This work is aimed to study the suitability of the wooden backbone of Opuntia ficus indica cladodes as reinforcement for the production of bio-composites. The wooden backbone can be extracted from O. ficus indica cladodes, which constitute a very relevant agricultural scrap, and is characterized by a thick walled cellular structure. In view of its potential in poly-lactic acid (PLA) matrix bio-composite production, two different possible applications were examined. In the first alternative, the wooden backbone was used in replacement of flax fibers for the production of fully consolidated bio-composites. Results obtained have shown that, though being characterized by lower properties compared to those of flax fiber composites, the opuntia actually works as an efficient reinforcement for PLA/wood flour matrix, increasing the flexural strength and elongation at break. In the second alternative, the cellular structure was used for the production of a sandwich bio-composite with a PLA/wood flour skin. In this case, the very high interlaminar adhesion strength between the skin and the core was considered as an indication of the potentiality of this material for the production of high strength sandwich structures. As a confirmation of this, no interlaminar debonding was observed during short beam tests.

The role of composite materials in the development of new advanced products for many industrial applicationsis strictly dependent on the reduction of materials and processing costs. High-performance composites areusually manufactured utilizing prepregs for lamination and an autoclave, where the curing process of thethermosetting matrix is completed by increasing temperature and pressure. Several composite parts arecommonly cured in the same autoclave leading to nonuniform thermal histories, which depend on theirposition inside the autoclave, and on the thermal inertia of parts. In this paper, we propose a mixed integerlinear programming model to optimize the composite part placement into an autoclave. The main decisionvariables determine the orientation and placement of parts in the autoclave, while the objective function isformulated to minimize the maximum overexposure of the curing process. The validity for practical use ofour model has been tested on a set of real cases

The need for new measurement techniques able to assess the nanofiller dispersion is still receiving great consideration when nanocomposites are developed. This occurs since different routes to disperse nanostructures generate molecular changes in polymer matrices that promote complex polymer–polymer and polymer–nanofiller interactions, which make difficult a suitable estimation of the dispersion. In this paper, ultrasonic waves at different frequencies and power were used for preparing nanocomposite samples and for evaluating the nanofiller dispersion. First, a patented method was used to disperse multiwall carbon nanotubes (MWCNTs) in polyamide 12 through extrusion assisted by low-frequency and high power ultrasound (with frequency ranging between 20 and 50 kHz). This “green” processing method was able to induce different states of dispersion of the nanofillers, as well as chemical modifications to polymer chains promoting branching reactions. Then, ultrasonic dynamic mechanical analysis (UDMA with ultrasound frequency in the megahertz range) was used to estimate the dispersion of the different nanocomposite samples. Compared to rheological measurement methods, UDMA provided a better estimation of the quality of dispersion, being sensitive both to the complex molecular architectures in polymer matrices and to the scattering due to MWCNT agglomerates.

A new procedure for the alignment of carbon nanotubes in a thermosetting matrix is proposed in this study. The two-step approach is based on (i) the alignment of carbon nanotubes (CNTs) in thermoplastic fibres by electrospinning and (ii) the transfer of these nanocompositefibres into a reactive thermosetting resin, in which they are easily soluble. After fibre dissolution, the CNTs remain aligned in the cured thermosetting matrix. The proof of concept is demonstrated by producing electrospunpolymethyl methacrylate (PMMA) fibres filled with single wall carbon nanotubes (SWCNTs) in the form of unidirectional tape, which are then solubilised into a vinylester (VE) matrix. The PMMA is easily dissolved by the styrene present in the VE resin, leaving SWCNTs aligned in the cured VE network, as confirmed by Raman spectroscopy studies. A 50% increase in elastic modulus (SWCNT 1.3 wt.%) has been obtained by dynamic mechanical analysis carried out in tensile mode at 1 Hz. Thanks to its ability to orient carbon nanotubes in a thermosetting matrix, the proposed method can be exploited also to transfer oriented nanofillers into continuous fibre composites, thus obtaining multiscale or hierarchical composites.

This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as “recycled plastic lumber”, is characterized by very poor mechanical properties, which results in high deflections under flexural loads, particularly under creep conditions. The Prowaste project, founded by the EACI (European Agency for Competitiveness and Innovation) in the framework of the Eco-Innovation measure, was finalized to develop an innovative technology for selective reinforcement of recycled plastic lumber. Selective reinforcement was carried out by the addition of pultruded glass rods in specific positions with respect to the cross section of the beam, which allowed optimizing the reinforcing efficiency. The reinforcement of the plastic lumber beams with pultruded rods was tested at industrial scale plant, at Solteco SL (Alfaro, Spain). The beams obtained, characterized by low cost and weight, were commercialized by the Spanish company. The present paper presents the most relevant results of the Prowaste project. Initially, an evaluation of the different materials candidates for the reinforcement of recycled plastic lumber is presented. Plastic lumber beams produced in the industrial plant were characterized in terms of flexural properties. The results obtained are interpreted by means of beam theory, which allows for extrapolation of the characteristic features of beams produced by different reinforcing elements. Finally, a theoretical comparison with other approaches which can be used for the reinforcement of plastic lumber is presented, highlighting that, among others, the Prowaste concept maximizes the stiffening efficiency, allowing to significantly reduce the weight of the components.

Adhesion is attracting increasing interest in the aerospace field since composite materials have become, together with aluminium alloys, the main structural materials for aircraft primary structures. Nano-graphite was demonstrated to improve the mechanical performance of several polymers used as composite matrices. In this work Single Lap Joints (SLJs) of unidirectional composite laminates were manufactured, tested and simulated: two families of specimens were investigated and compared, one joined using conventional epoxy resin, the other joined with an adhesive obtained mixing the same epoxy resin with nano-graphite particles. The dispersion of expanded and sonicated graphene stacks (EGS, 3% wt) in the epoxy matrix was obtained by the swelling method, dispersing first the filler in acetone and then mixing it with the epoxy oligomers. Finally the solvent was evaporated and the filler-epoxy mixture was degassed under vacuum before adding an amine curing agent in a stoichiometric quantity. The research demonstrates the superior mechanical properties of the adhesive with the addition of nano-graphite through experimental characterization of its behaviour in terms of strength and energy absorption. Finite element numerical simulations have been carried out using the Cohesive Zone Model (CZM) element, obtaining as parameters the maximum shear stress and the critical fracture energy for the two adhesives. A good correlation between numerical and experimental results has been achieved and the criteria for developing reliable and accurate non-linear models of the adhesive failure have been established.

The objective of this work is to study the sintering behavior of polyamide 6 (PA6) powders and PA6 nanocomposites by means of thermomechanical (TMA) and dimensionless analysis in view of its technological application in rotational molding. TMA analysis was used to monitor the bulk density evolution of PA6 powders and PA6 nanocomposites when heated above the melting temperature. Experimental TMA results indicate that the sintering of PA6 and PA6 nanocomposites occurs in two different steps, namely powder coalescence and void removal. Furthermore, TMA analysis also showed that relevant degradation phenomena occur during the sintering of PA6 and PA6 nanocomposites, leading to gas formation in the molten polymer. The suitability of these materials in rotational molding was then assessed by defining a processing window, as the temperature difference between the endset sintering and the onset degradation. The heating rate dependence of the processing window was explained by means of dimensionless analysis, showing that powder coalescence is influenced by the viscosity evolution of the matrix, whereas void removal is influenced by the gas diffusivity inside the molten matrix. Therefore, the diffusion activation energy correlates the endset sintering temperature to the heating rate. On the other hand, the onset degradation temperature depends on the heating rate, due to the characteristic activation energy of the degradation process. Accordingly, the width of the processing window mainly depends on the values of the activation energies for diffusivity and degradation. The width of the processing window for neat PA6 was found to be too narrow to candidate this polymer for rotational molding. The addition of nanofiller causes a narrowing of the processing window, whereas the PA6 matrix modified with a thermal stabilizer showed a sufficiently broad processing window, compatible for use in rotational molding

An overview of the current state of art of the ultrasonic treatment technology applied to polymer melts is presented. The research and technological advancements of the ultrasonic treatment as applied to development of polymeric materials are discussed. An analysis of the technological progress shows that the mechanism of the effects of ultrasound on polymer melts is not fully understood at present. Such lack in fully understanding the mechanism could limit the use of this versatile technology in future applications. Based on the critical analysis of the research progress to date, some key issues for a deeper understanding of the chemical and physical effects of ultrasound on polymer melts are identified.

The design of a tracking detector for electrons in a magnetic field consisting of a drift chamber is discussed. The chosen materials for its construction must be light to minimize the effects of the subatomic particles interactions with the chamber walls. Low-density materials and very thin wall thicknesses are therefore needed. From a mechanical engineering point of view, it is important to analyse the drift chamber structure and define the conditions to which it is subject in terms of both mechanical loads and geometric constraints. The analysis of the structural response of the drift chamber has been performed through the Finite Element Method (FEM) as implemented in the commercial software ANSYS and (Ansys Composite Pre/Post).

The aim of this work is the analysis of ageing phenomenon occurring in amorphous thermoplastic polymers below their glass transition temperature by pressure-volume-temperature (PVT) analysis. The ageing behavior of different polymers as a function of the heating and cooling rates has been widespread studied. Also, different works in literature are aimed to study the effect of the applied pressure on the glass transition behavior. Another relevant aspect related to the glass transition behavior is related to the ageing effects, which can also be influenced by the applied pressure. This is a very relevant issue, since most of the polymers, during ageing, are subjected to mechanical loading. PVT analysis was used to study the ageing of amorphous PET copolymer (PETg) at different pressure levels. Specific volume-temperature curves measured during the cooling and the heating steps were used for calculating the relaxed specific volume, showing that ageing effects increase with increasing applied pressure. The evolution of the fictive temperature as a function of time was calculated from experimental data.

ABSTRACT: The aim of this work is to characterize the rheological and permeability behavior of nanocomposites based on amorphous poly(ethylene terephthalate) (PETg) and organically modified montmorillonites (omMMT), obtained by melt intercalation. The use of PETg instead of semicrystalline PET is believed to reduce the risks associated to organic modifier degradation during processing at high temperatures. X-ray and transmission electron microscopy analysis performed on the PETg nanocomposites showed that processing for long time at temperatures lower than melting of semicrystalline PET allowed to obtain a partially intercalated structure with some degree of exfoliation. The rheological behavior of PETg nanocomposites was studied as a function of shear rate in a cone– plate rheometer in order to correlate the viscosity with the aggregation state of omMMT. A simple model accounting for an apparent increase of rheological units size, associated with the intercalation of PETg macromolecules into omMMT galleries, is proposed. The glass transition temperature, Tg, as a function of the volume fraction of omMMT content of the nanocomposite, was measured using differential scanning calorimetry. Finally, the water vapour permeability of PETg nanocomposites was correlated to the volume fraction of the impermeable inorganic part of the omMMT.

This paper is aimed to study the suitability of poly(lactic acid) (PLA) for the production of biodegradable containers by rotational molding. To increase polymer toughness, PLA was plasticized with poly(ethylene glycole) (PEG), with an average molecular weight of 400 g/mol. Differential scanning calorimetry performed on neat PLA and PEG-plasticized PLA showed that the former is characterized by a better quenchability than the latter. Neat PLA and PEG-plasticized PLA were used for the production of rotational molding prototypes of simple shape. Owing to its very slow crystallization kinetics, a completely amorphous PLA was obtained by rotational molding with air cooling. As a consequence, rotomolded PLA is characterized by a good ductility and toughness. In contrast, the higher crystallization rate induced by the addition of PEG did not allow to obtain an amorphous structure for plasticized PLA, even if faster cooling was attained by water spraying. As a consequence, the PEG-plasticized PLA, characterized by a semicrystalline structure, shows a lower ductility and toughness compared to neat PLA.

In haemodialysis patients, the risk of bacteremia associated to the use of vascular access is very high; many reports count the use of both tunnelled and not tunnelled catheters as one of the major cause of infections. The use of silver in modern medicine is growing thanks to its strong biocide activity against a broad spectrum of bacteria and fungi and its good degree of biocompatibility. In this study an innovative and patented technology has been used for superficial treatment of polyurethane haemodialysis catheters with silver.

Antibacterial coatings on catheters for acute dialysis were obtained by an innovative and patented silver deposition technique based on the photo-reduction of the silver solution on the surface of catheter, with consequent formation of antibacterial silver nanoparticles. Aim of this work is the structural and morphological characterization of these medical devices in order to analyze the distribution and the size of clusters on the polymeric surface, and to verify the antibacterial capability of the devices treated by this technique against bacterial proliferation. The structure and morphology of the silver nanoparticles were investigated by using scanning and transmission electron microscopy. The antimicrobial capability of the catheters after silver deposition was confirmed by antibacterial tests with Escherichia coli. Both scanning electron microscopy analysis and antibacterial tests were performed also after washing catheters for 30 days in deionized water at 37°C, relating these data to thermogravimetric analysis and to energy dispersive spectroscopy, in order to check the resistance of coating and its antimicrobial capability after the maximum time of life of these devices.

In the public transport system, hand-touch surfaces such as seats in buses, trains, trams, and airplanes represent a reservoir of bacteria and a potential risk for contamination among passengers. The antimicrobial activity of silver has been known since ancient times. In this work, natural leather commonly used in the public transport system was treated with silver through the in situ photoreduction of a silver solution. The morphology of the coating and the distribution of silver clusters were studied by scanning electron microscopy and by energy dispersive X-ray spectroscopy. The amount of silver on the surface was quantified by thermo-gravimetric analysis. The antibacterial capability of the treated materials was checked against Gram-positive and Gram-negative bacteria. Taber test was conducted on silver treated samples in order to study the durability of the treatment. The morphology of the silver coating and its antibacterial capability were analyzed also after the Taber test.

Over the last few years different antibacterial technologies have been developed in order to obtain fabrics and fibers with antibacterial capabilities for use in hospital environments. High levels of sanitation are indeed required in order to reduce nosocomial cross-transmission of infections. Silver-coated fibers are particularly appealing for the production of antibacterial textiles, due to the outstanding properties of silver, characterized by a high degree of biocompatibility, an excellent resistance to sterilization conditions, and antibacterial properties with respect to different bacteria, associated with long-term efficiency. In this study an innovative patented low-cost technique to deposit silver on natural and synthetic substrates has been exploited to obtain silver-coated natural fibers (i.e. cotton and flax). Such natural fibers are largely used in the hospitals for the production of sheets, pillowcases and other textile products that should possess high levels of sanitation. The structure and morphology of the silver nanoclusters deposited onto natural fibers was observed by scanning electron microscopy (SEM), and the coating was quantitatively assessed by thermogravimetric analysis (TGA). Good silver coating stability resulted from several industrial washings performed on the samples. The antimicrobial capabilities of the treated fibers were confirmed by antibacterial tests with Escherichia Coli. Silver-coated natural fibers thus show potential for the development of antibacterial textiles with long-term efficiency that is particularly useful in healthcare settings.

This study is aimed at the synthesis of antimicrobial hydroxyapatite (HAP)‐based composites for dental application by stereolithography (SLA). A micron‐sized commercial HAP was modified by methacrylate and quaternary ammonium salt, and, then, it was used in different amounts (namely 2.5, 5, and 10 wt%) as filler for a photocurable custom made resin for SLA. Thermal stability, microstructure, and particles size of the pristine (HAP) and modified HAP (mHAP) were evaluated by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and particle size analyser (CILAS). The suitability of each formulation for stereolithography process was assessed by measuring viscosity, degree of conversion (DC%) by Fourier transform infrared spectroscopy (FTIR), glass transition temperature, and thermal stability. Photo‐cured specimens for physical, mechanical, and antimicrobial testing were built by SLA. The flexural strength of the samples was measured using a 3‐point bending test method, and the fractured surface was analysed by scanning electron microscopy (SEM). The antimicrobial activity of samples was investigated against some standard microorganisms (Staphylococcus aureus, Escherichia coli, and Candida albicans), as representative Gram positive and Gram negative bacteria and fungus, respectively. The flexural strength increased with a filler content up to 5% and slightly decreased for higher content. SEM analysis confirmed the presence of uniformly distributed HAP. The incorporation of mHAP reduced the bacterial and fungal growth in dose‐dependent manner in comparison with the neat samples. Finally, a prototype of dental bite was built by SLA.

The aim of the present article is to study the different phenomena which are at the basis of the consolidation of commingled thermoplastic semi-pregs made of amorphous polyester fibers and E-glass reinforcement. The evolution of the void fraction during the consolidation of the composite was monitored by a dynamometer, equipped with parallel plates and a forced convection oven. Different physical changes were associated to the consolidation temperature. Scanning electron microscopy (SEM) and thermomecahnical analysis (TMA) showed that at low temperature, matrix fiber deformation and sintering are responsible of the initial void reduction. At a temperature higher than the onset of the flow region, reinforcement impregnation is responsible of the further void reduction. Dimensionless analysis confirmed that at lower temperatures, corresponding to higher viscosities, consolidation due to viscous flow of the polymer matrix is negligible compared to consolidation due to sintering of matrix fibers. The results indicate that the Darcy law can efficiently represent the consolidation during the microscale impregnation of the reinforcement, but cannot account for the initial stages of consolidation.

Thermoplastic materials are getting increasing attention in the aerospace field for a wide range of applications not only related to primary structures. In this work two types of thermoplastic structures are manufactured and investigated: a L-shaped stringer used as stiffener of flat plates; a stiffened panel for aerospace applications. The panel has been reinforced using four L-shaped stringers joined to it by induction welding, an innovative technique alternative to mechanical fastening and adhesive bonding. The main focus of this work is experimentally demonstrating the capability of the welding to keep properly the loads arising from a compression test until the failure of the stiffened panel. Interesting results came out concerning the post-buckling behaviour of the adopted thermoplastic materials that exhibited outstanding load bearing capabilities.

This work is aimed to study the suitability of a bio based compound, cardanol acetate (CA), as plasticizing agent of poly(lactic acid) (PLA). Compared to other natural derived plasticizers, cardanol acetate is not obtained from food crops but as a by product of cashew nut extraction. In addition, the cardanol derived plasticizers can be obtained by the use of non toxic and low environmental impact reagents. The plasticizing effectiveness of cardanol acetate was confirmed by the decrease of the glass transition temperature and flexural modulus, which were comparable to those obtained by the use of conventional oil based plasticizers, such as diethylhexyl phthalate (DEHP). In addition, calorimetric analysis revealed that the addition of the plasticizer, both cardanol derived and phthalate, involves a significant increase of the crystallization kinetics. An analysis of the flexural strength and deformation at break indicated that the increase of the crystallization kinetics has more dramatic effects compared to the decrease of the glass transition, particularly at low plasticizer content, finally leading to a decrease of the ductility. At higher plasticizer content, an increase of the ductility is observed, and PLA plasticized by 10% of CA showed a significant higher deformation at break than PLA plasticized by DEHP. In addition, plasticizer migration tests showed a lower weight loss of PLA plasticized by CA compared to DEHP plasticized PLA, which indicates the potential higher stability of properties of the cardanol derived plasticizer.

The strong influence of graphite oxide (GO) nanofiller on the glass transition temperature (Tg) of epoxy resins, generally attributed to restricted molecular mobility of the epoxy matrix by the nanofiller or to the crosslinking of GO layers via the epoxy chains, is investigated. The study confirms that large increases of the glass transition temperature of the nanocomposite can be observed in presence of GO. However, similar Tg increases are observed, when the filler is a high-surface-area graphite (HSAG), lacking oxidized groups. Moreover, these Tg differences tend to disappear as a consequence of aging or thermal annealing. These results suggest that the observed Tg increases are mainly due to a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and diamine), rather than to reaction of the epoxide groups with functional groups of GO. This hypothesis is supported by investigating the catalytic activity of graphite-based materials on reactions between analogous monofunctional epoxide and amine compounds

This article compares the catalytic activities of oxidized carbon black (oCB) and graphene oxide (eGO) samples on the kinetics of a reaction of diglycidyl ether of bisphenol A (DGEBA) with a diamine, leading to crosslinked insoluble networks. The study is mainly conducted by rheometry and Differential Scanning Calorimetry (DSC). Following the same oxidation procedure, CB samples are more efficiently oxidized than graphite samples. For instance, CB and graphite samples with high specific surface areas (151 and 308 m2/g), as oxidized by the Hummers’ method, exhibit O/C wt/wt ratios of 0.91 and 0.62, respectively. Due to the higher oxidation levels, these oCB samples exhibit a higher catalytic activity toward the curing of epoxy resins than fully exfoliated graphene oxide.

Sulla base dei risultati ottenuti in precedenti studi ed in considerazione dell’impatto ambientale che lo smaltimento dei pneumatici pone ancora in Italia, la Regione Puglia ha finanziato un Progetto di Ricerca dal titolo “Impiego di particelle di gomma e fibre d’acciaio provenienti da pneumatici fuori uso in conglomerati cementizi”, sviluppato dall’Università del Salento . Nell’ambito di detto Progetto è stata condotta un’indagine sperimentale finalizzata alla valutazione delle proprietà meccaniche di calcestruzzi rinforzati con fibre di acciaio provenienti da PFU, (RSFRC -Recycled Steel Fiber Reinforced Concrete) e di calcestruzzi ottenuti con l’aggiunta di particelle di gomma in sostituzione di parte dell’inerte (Rubcrete). Nel lavoro sono riportati i principali risultati ottenuti in seguito al suddetto Progetto di Ricerca.

A significant effort was directed to the synthesis of graphene stacks/epoxy nanocomposites and to the analysis of the effect of a graphene precursor on cure reaction of a model epoxy matrix. A comparative thermal analysis of epoxy resins filled with an exfoliated graphite oxide eGO were conducted. The main aim was to understand the molecular origin of the influence of eGO on the Tg of epoxy resins. The higher Tg values previously observed for low curing temperatures, for epoxy resins with graphite-based nanofillers, were easily rationalized by a catalytic activity of graphitic layers on the reaction between the epoxy and amine groups of the resin, which leads to higher crosslinking density in milder conditions. A kinetic analysis of the cure mechanism of the epoxy resin associated to the catalytical activity of the graphite based filler was performed by isothermal DSC measurements. The DSC results showed that the addition of graphite based filler greatly increased the enthalpy of epoxy reaction and the reaction rate, confirming the presence of a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine). A kinetic modelling analysis, arising from an auto-catalyzed reaction mechanism, was finally applied to isothermal DSC data, in order to predict the cure mechanism of the epoxy resin in presence of the graphite based nanofiller.

Reactive compounds in thermosetting matrices of composite materials are monomers or oligomers characterized by a functionality that ranges from a minimum of two up to six or more, in order to produce a crosslinked network. The generic term of resin is usually referred either to the monomer present in the larger amount either to the mix containing the main monomer and all other reactive components, i.e. curing agents, catalysts and initiators. The same base monomer can thus be used to produce crosslinked polymers characterized by properties strongly different depending on the curing agents. In this section, the curing agents involved in and strictly necessary to the curing reactions, are only considered. In very basic terms, curing agents are divided in two classes depending on the role they play in the curing reactions. In step reactions curing agents participate to form the crosslinked network being present in a significant amount and are often referred as hardeners. In radical chain reactions the initiator, producing the first radical promoting the initiation step, is present in a very limited amount in the reactive mixture (a few percent by weight). The discussion will be essentially limited to epoxy resin and partly to polyester and vinylester resins.

The aim of the present work is the development of amorphous thermoplastic matrix nanocomposites based on graphite nanoparticles. Different types of graphite were used, including unmodified graphite, graphene nanoplatelets and graphite intercalation compounds. Graphite intercalation compounds were subjected to thermal treatment to attain exfoliation of the nanofiller. The exfoliation process was studied by means of thermal analysis. The nanofillers and nanocomposites were characterized by means of X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analysis. The nanocomposites were further characterized by means of mechanical and dielectric analysis. The flammability of the nanocomposites was also analyzed. Results obtained indicate that addition of the nanofiller allows improving the proprieties of the amorphous thermoplastic matrix. The effect of the degree of dispersion of the nanofiller is particularly relevant for the dielectric properties of the nanocomposites, whereas no direct correlation between degree of dispersion and mechanical properties can be observed.

In the last decade cellulose-based hydrogels have been receiving increasing attention for a number of applications, due to their smart swelling behaviour, biodegradability and biocompatibility. Given the dramatic spreading of obesity and overweight in the industrialized countries and the lack of scientific consensus over currently available dietary supplements, it was recently proposed that such hydrogels might be used as orally administered bulking agents in hypocaloric diets, since the hydrogel swelling in the stomach may greatly reduce the space available for food intake, thus giving a sense of fullness. This study focused on the synthesis of cellulose-based hydrogels, starting from pharmaceutical and food grade cellulose derivatives, and showed that such hydrogels possess good swelling properties in water solutions mimicking the environmental conditions of the stomach and the intestine, as well as a good biocompatibility. The crosslinking agent used was a ‘zero-length’ crosslinker, i.e. a water soluble carbodiimide, which is washed out from the gel after the synthesis and does not affect the gel compatibility, as shown by preliminary biocompatibility assays. The experimental results confirmed that cellulosebased hydrogels might be a scientifically valid dietary adjuvant in the treatment of obesity and overweight, and provide further scientific evidence for future experiments on humans.

The need for reconstructing complex bone defects in the maxillofacial region as a result of trauma, tumor surgery or congenital malformation has become a hot topic in the field of tissue engineering. Tools such as 3D computer aided design (CAD) systems and rapid prototyping (RP) machines can be exploited to fabricate custom made bone scaffolds. RP techniques allow the construction of complex physical models based on 3D clinical images elaborated by suitable software and CAD systems. Hydroxyapatite (HA) is one of the most commonly used materials for bone reconstruction because of its close similarity in composition to human bone and teeth. Thus, producing a custom-made scaffold from a ceramic material directly by RP represents an exciting challenge. The aim of this paper is the development of a suspension of HA powder dispersed in an UV curable epoxy based resin, suitable for stereolithography (SLA). The influence of different HA concentrations within the ceramic suspension on the kinetics of the photochemical reaction was firstly investigated. The rheological behavior of the same ceramic suspensions was also analyzed by verifying the effect of HA on the viscosity and the stability of the suspensions as a function of the shear rate and the time from preparation. After the selection of a suitable suspension, simple green ceramic bars built by stereolithography and sintered with an appropriate thermal cycle, were built and characterized, showing good mechanical properties. A complex prototype, starting from a CAD model, was finally built by a SLA apparatus

Hyperhidrosis, or excessive sweating, is an overlooked and potentially disabling symptom, which is often seen in social anxiety disorder. In this work an innovative advanced textile material was developed for application in the management of excessive sweating, preparing a drying yarn providing improved comfort. Hybrid cotton/hydrogel yarns were obtained by combining cotton with superabsorbent hydrogels through an optimization study focused on the achievement of the most promising product in terms of absorption properties and resistance to washings. Swelling and washing tests were performed using different hydrogels, and the effect of an additional crosslinking on the materials was also evaluated by testing different solutions containing Al(3+) and Ca(2+) ions. Scanning electron microscopy and infrared spectroscopy analyses were adopted to characterize morphology and chemical structure of the hydrogels undergoing different production processes. The biocompatibility of the hybrid fabrics was demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) through the extract method.

Purpose: The objective of this work was to develop composite hydrogels based on poly(ethylene glycol) diacrylate (PEGDA) and collagen (Coll), potentially useful for biomedical applications. Methods: Semi-interpenetrating polymer networks (semi-IPNs) were obtained by photo-stabilizing aqueous solutions of PEGDA and acrylic acid (AA), in the presence of collagen. Further grafting of the collagen macromolecules to the PEGDA/poly(AA) network was achieved by means of a carbodiimide-mediated crosslinking reaction. The resulting hydrogels were characterized in terms of swelling capability, collagen content and mechanical properties. Results and conclusions: The grafting procedure was found to significantly improve the mechanical stability of the IPN hydrogels, due to the establishment of covalent bonding between the PEGDA/poly(AA) and the collagen networks. The suitability of the composite hydrogels to be processed by means of stereolithography (SLA) was also investigated, toward creating biomimetic constructs with complex shapes, which might be useful either as platforms for tissue engineering applications or as tissue mimicking phantoms.

This work is aimed to study the diffusion process in oriented nanocomposites, characterized by the presence of permeable lamellar stacks, by FEM analysis. To this purpose, a geometrical model, based on a random distribution of non-interpenetrating stacks, was used to calculate the coefficient of diffusion. The main novelty of the developed analysis is that each nanofiller particle is made by a stack of individual platelets, separated by galleries of varying thickness. Consequently, the nanofiller particles are not considered to be completely impermeable to the diffusing species, thus allowing to account for mass transport between stacks, as well as within each stack. Simulations were run at different nanocomposites morphologies, varying nanofiller volume fraction, orientation angle, lamellar gallery thickness and number of platelets in each stack. An analytical model was developed, which is able to predict the evolution of coefficient of diffusion as a function of the four morphologic features of the nanocomposites. The developed model can account for the multi scale diffusion mechanism, showing a very good agreement with the simulation data. The developed analytical model was used to estimate the orientation angle of graphene stacks in epoxy matrix by comparison with experimental permeability data.

To evaluate the diagnostic performance of gold nanorod (GNR)-enhanced optoacoustic imaging employing a conventional echographic device and to determine the most effective operative configuration in order to assure optoacoustic effectiveness, nanoparticle stability, and imaging procedure safety. The most suitable laser parameters were experimentally determined in order to assure nanoparticle stability during the optoacoustic imaging procedures. The selected configuration was then applied to a novel tissue-mimicking phantom, in which GNR solutions covering a wide range of low concentrations (25-200 pM) and different sample volumes (50-200 μL) were exposed to pulsed laser irradiation. GNR-emitted optoacoustic signals were acquired either by a couple of single-element ultrasound probes or by an echographic transducer. Off-line analysis included: (a) quantitative evaluation of the relationships between GNR concentration, sample volume, phantom geometry, and amplitude of optoacoustic signals propagating along different directions; (b) echographic detection of "optoacoustic spots," analyzing their intensity, spatial distribution, and clinical exploitability. MTT measurements performed on two different cell lines were also used to quantify biocompatibility of the synthesized GNRs in the adopted doses. Laser irradiation at 30 mJ/cm(2) for 20 seconds resulted in the best compromise among the requirements of effectiveness, safety, and nanoparticle stability. Amplitude of GNR-emitted optoacoustic pulses was proportional to both sample volume and concentration along each considered propagation direction for all the tested boundary conditions, providing an experimental confirmation of isotropic optoacoustic emission. Average intensity of echographically detected spots showed similar behavior, emphasizing the presence of an "ideal" GNR concentration (100 pM) that optimized optoacoustic effectiveness. The tested GNRs also exhibited high biocompatibility over the entire considered concentration range. An optimal configuration for GNR-enhanced optoacoustic imaging was experimentally determined, demonstrating in particular its feasibility with a conventional echographic device. The proposed approach can be easily extended to quantitative performance evaluation of different contrast agents for optoacoustic imaging.

The growing use of reinforcement preforms during composite manufacturing requires resin soluble binders which significantly affect the properties of crosslinking thermosetting resins. In this study, for the first time the influence of an epoxy preforming binder on the curing kinetics and chemorheological behavior of a crosslinking epoxy matrix was studied. The results proved that the addition of the binder lead to a significant change of the curing behavior suggesting that the epoxy binder was an essential component needed to complete the stoichiometry of the resin-hardener mixture. The developed kinetic and chemorheological model of the experimental results could be used for process optimization

Abstract This paper is aimed to study the morphology of intercalated nanocomposites, by coupling experimental permeability data with different analytical models. X-Ray diffraction provided the reference morphological features of the nanocomposite, including gallery thickness and aspect ratio of the lamellar stacks. Afterward, the water permeability of two intercalated nanocomposites was used for the calculation of the nanofiller aspect ratio, following different approaches. The obtained results indicate that an assumption of impermeable stacks involves a significant over- estimation of the nanofiller aspect ratio. Further, when the morphological features determined in the assumption of impermeable particles are used for estimation of the nanocomposite diffusivity by the use of the Fricke model, results do not show a satisfactory agreement with experimental data. On the other hand, fitting experimental permeability data with an analytical model accounting for intra-stack diffusion provided an estimation of the nanofiller aspect ratio in excellent agreement with that obtained by XRD. Further, applying the Fricke equation with the morphological features determined by the permeable stack model, an excellent agreement to the experimental data was obtained. The results indicate the relevance of intra-stack diffusion in intercalated nanocomposite, and the need to account for it when modeling mass transfer in nanocomposites.

The aim of this work is to study the effect of an organically modified clay on the structural relaxation behavior of an amorphous thermoplastic matrix. Differential scanning calorimetry (DSC) and pressure–volume–temperature (PVT) analysis were used in order to calculate the relaxation enthalpy and specific volume of the neat matrix and the nanocomposite during ageing below the glass transition region. Stress relaxation experiments were used to measure the characteristic relaxation time of the materials at different temperatures below glass transition. DSC and PVT analysis both revealed that relaxation phenomena are more relevant for the nanocomposite compared to the neat matrix. This result was confirmed by stress relaxation measurements, which indicates that below the glass transition the relaxation times of the nanocomposite are lower than those of the neat matrix. The enhanced relaxation behavior of the nanocomposite compared to the neat matrix was attributed to the presence of the organic modifier, which, acting as a plasticizer for the matrix, enhances its molecular mobility. The presence of low glass transition portions in the matrix was also evidenced by DSC and dynamic mechanical analysis.

This work is aimed to the development and property optimization of cardanol derived plasticizers. To this purpose, different plasticizers were produced though different epoxidation routes, characterized by low toxicological and environmental impact. The plasticizers are characterized by different yield of epoxidation of the alkyl chain double bonds. The properties of the cardanol derived plasticizers were compared to the properties of commercial plasticizers, either phthalates or natural derived. Mechanical properties of soft PVC plasticized by cardanol derivatives were shown to be comparable to those of PVC with commercial plasticizers. The plasticizing efficiency of cardanol derivatives was significantly improved by increasing the yield of epoxidation. Also, mechanical properties performed after ageing showed the excellent stability of the properties of the cardanol derived plasticizer characterized by the higher yield. Evaluation of the property retention index after ageing indicated that such plasticizers showed an improved stability of properties compared to other commercial plasticizer. The results obtained highlight the relevance of an high conversion of the double bonds into epoxies in order to produce high quality plasticizers.

Soft PVC was obtained by using a new plasticizer, based on cardanol, a renewable resource characterized by chemical and physical properties very close to those of diethylhexyl phthalate (DEHP). Cardanol acetate (CA) was obtained by solvent free esterification of cardanol, and used as secondary plasticizer, by partial substitution of DEHP in soft PVC formulations. Ageing tests were performed in order to study the stability of properties of the soft PVC formulations related to plasticizer diffusion. Tensile properties and hardness changes were used to monitor the macroscopic effects of plasticizer diffusion. Soft PVC obtained by partial substitution of DEHP by CA showed a significant modification of mechanical properties related to a higher plasticizer evaporation during ageing tests. Migration tests confirmed that CA is characterized by a higher diffusivity in soft PVC compared to DEHP.

Surface engineering based on the application of silver nanoparticles is emerging as one of the most promising in the nanotechnology field. The well-known antimicrobial activity of silver is emphasized by the high specific surface which grows inversely to the particle dimensions. In this chapter, various properties and applications of antibacterial silver coating are reviewed. In particular, an innovative deposition technology of silver nanoclusters on various natural and synthetic substrates developed by the authors is described. The deposition of strongly adhered silver nanostructures was obtained by a wet chemical method followed by a UV curing process. A very close view of the microstructure of the silver nanoclusters on the coated substrates has been obtained using advanced diagnostic tools: TEM, SEM, EDX. The strong antimicrobial capabilities of the treated substrates was evidenced with systematic antibacterial tests with Escherichia coli.

Graphene stacks/epoxy nanocomposites were produced and characterized in order to analyse the effect of different graphene precursors on cure reaction of a model epoxy matrix. A kinetic analysis of the cure mechanism of the epoxy resin associated to the catalytical activity of the graphite based fillers was performed by isothermal DSC measurements. The DSC results showed that the addition of all graphite based fillers greatly increased the enthalpy of epoxy reaction and the reaction rate, confirming the presence of a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine). A kinetic modelling analysis, arising from an autocatalyzed reaction mechanism, was finally applied to isothermal DSC data, in order to predict the cure mechanism of the epoxy resin in presence of the graphite based nanofiller.

The aim of this paper is a comparison of the effectiveness of different macrocharacterization techniques for the prediction of the degree of dispersion and intercalation of bidimensional nanofillers in an amorphous thermoplastic matrix. Organically modified montmorillonites (omMMT) were used as bidimensional nanofillers, whereas amorphous polyethylene-terephthalate copolymer (PETg) was used as matrix. Wide angle xray diffraction analysis showed no relevant difference between the samples processed at different temperatures, all characterized by a predominantly intercalated structure. On the other hand, transmission electron microscopy (TEM) analysis showed the presence of some degree of exfoliation, as well as the presence of lamellar stacks of different thickness. The aspect ratio of lamellar stacks was estimated by means of rheological, mechanical, and gas permeability analysis. All techniques provided values which are in quite good agreement with TEM analysis. Furthermore, all techniques were able to capture the increase in the lamellar stack aspect ratio with decreasing processing temperature.

This work is aimed to study the diffusion in 3D nanocomposites obtained with stacks of lamellar nanofillers characterized by the presence of permeable galleries, by finite element (FE) analysis. To this purpose, a geometric model, based on a randomdistribution of noninterpenetrating stacks,with each one beingmade of regularly spaced lamellae, was developed.The developedmodel is able to account for diffusion between stacks (interstack diffusion) as well as diffusion inside stacks (intrastack diffusion). Simulation results showed that intrastack diffusion, related to flowinside galleries, can be quite relevant, particularly at high values of gallery thickness. Comparison of the simulation results with literature models shows that when intrastack diffusion is not taken into account, the diffusion behavior in intercalated nanocomposites is not well predicted. Therefore, intrastack permeability of nanofillers such as organic modified clays cannot be neglected. Such intrastack diffusivity is shown to depend on the morphological features of the nanofiller requiring the development of a proper mathematical model.

Continuous inductionwelding for thermoplasticmatrix composites requires an accuratemodeling of the temperature distribution in the laminates, depending on the electromagnetic field. In this work, a transient threedimensional finite element (FE)model was developed in order to study the heat transfer phenomena, and melting and crystallization in the welding area during the continuous induction welding of carbon fiber reinforced Poly(ether ether ketone) (CF/PEEK) laminates. The multiphysics problemwas solved by coupling electromagnetic and heat transfer equations considering matrix melting and crystallization behavior. The model was able to simulate the continuous process along a linear path at a constant speed. The computed temperatures were in good agreement with experimental measurements. Several numerical simulation were used for selecting a processing window as a function of coil speed and current, for the welding of CF/PEEK joints. The results of welding experiments were evaluated by single lap shear tests and morphology characterization of the welded interfaces and fracture surfaces.

This work is aimed to study the mass transport in 3D nanocomposites, characterized by the presence of permeable lamellar stacks, by means of finite element (FE) analysis. To this purpose, a geometric model was developed, based on a random distribution of non-interpenetrating stacks, each one made of regularly spaced platelets, which are considered representative of an intercalated nanocomposite. The morphological features of the stacks are the number of lamellae and the thickness of lamellar galleries, which determine the thickness, and therefore the aspect ratio. FE simulation results showed the relevance of diffusion within stack, and therefore the unsuitableness of the assumption of stack impermeability. The diffusion behavior of nanocomposites made of permeable stacks was modeled by considering the probability of collision of diffusing particles on the stack surface. For a random orientation of stacks, the developed analytical model showed an excellent agreement with the FE simulation results. It was shown that other analytical models found in literature are not able to capture the dependence of diffusivity on the morphology of intercalated nanocomposites. The developed analytical model allowed estimating the error arising from the assumption of impermeable stacks in the estimation of nanofiller aspect ratio from experimental diffusivity data.

The influence of different graphite-based nanofillers on epoxide ring opening reactions, as induced by amines for diglycidyl ether of bisphenol A (DGEBA), is studied. Direct kinetic studies, with full chemical characterization and quantitative evaluation of the low molecular mass products, for reactions of DGEBA with primary and secondary monoamines as well with alcohols, are conducted. Moreover, the kinetic behavior of a commercial epoxy resin based on DGEBA and a diamine, leading to crosslinked insoluble networks, is studied by indirect methods, such as differential scanning calorimetry (DSC) and rheometry. The reported results show a relevant catalytic activity of graphene oxide on epoxy resin crosslinking by amines. For instance, for a graphene oxide content of 3 wt%, the exothermic crosslinking DSC peak is shifted (upon heating at 10 C min1) from 113 C down to 96 C, while the gel time at 50 C is reduced by a factor of 2.5. This behavior is due to the ability of graphene oxide to catalyze primary amine–epoxy, secondary amine–epoxy and mainly hydroxyl–epoxy additions.

Rationale and Objectives: The aim of this study was to identify the optimal parameter configuration of a new algorithm for fully automatic segmentation of hepatic vessels, evaluating its accuracy in view of its use in a computer system for three-dimensional (3D) planning of liver surgery. Materials and Methods: A phantom reproduction of a human liver with vessels up to the fourth subsegment order, corresponding to a minimum diameter of 0.2 mm, was realized through stereolithography, exploiting a 3D model derived from a real human computed tomographic data set. Algorithm parameter configuration was experimentally optimized, and the maximum achievable segmentation accuracy was quantified for both single two-dimensional slices and 3D reconstruction of the vessel network, through an analytic comparison of the automatic segmentation performed on contrast-enhanced computed tomographic phantom images with actual model features. Results: The optimal algorithm configuration resulted in a vessel detection sensitivity of 100% for vessels > 1 mm in diameter, 50% in the range 0.5 to 1 mm, and 14% in the range 0.2 to 0.5 mm. An average area overlap of 94.9% was obtained between automatically and manually segmented vessel sections, with an average difference of 0.06 mm2. The average values of corresponding false-positive and false-negative ratios were 7.7% and 2.3%, respectively. Conclusions: A robust and accurate algorithm for automatic extraction of the hepatic vessel tree from contrast-enhanced computed tomographic volume images was proposed and experimentally assessed on a liver model, showing unprecedented sensitivity in vessel delineation. This automatic segmentation algorithm is promising for supporting liver surgery planning and for guiding intraoperative resections.

Ultrasonic metal welding has been applied for joining aluminum AA5754 sheets to a thermoset matrix composite consisting in a carbon fiber reinforced epoxy resin (CF/epoxy). To overcome the limitations of thermosetting resins, that, unlike thermoplastic polymers, cannot melt due to their chemical structure, a thermoplastic film of Polyamide 6 (PA6) has been used as a surface layer of the CF/epoxy stack before curing. The functional surface created on the thermoset matrix composite enables a fast welding with a metallic sheet. By a proper selection of welding energy and force, an average adhesion strength of 34.8 MPa has been obtained on CF/epoxy-PA6-AA5754 ultrasonically welded joints. The morphological characterization has revealed that the aluminum-composite interface is characterized by carbon fibers in a direct contact or even embedded in aluminum, whose surface presents pores and crevices due to the pronounced plastic deformation of the Al interfacial area

Abstract Two fusion bonding techniques typically used for thermoplastic matrix composites, such as ultrasonic and induction welding, were applied for joining thermosetting matrix composites. A proper modification of the composite layup was proposed, i.e. a thermoplastic film of Poly-vinyl butyral (PVB) was added as a last ply in the stacking sequence of carbon fibre epoxy prepregs, typically used in aeronautical applications. After matrix curing, an intermingled thermoplastic-thermoset polymer zone at the surface of composite was obtained. The composite containing the thermoplastic film was used for fabrication of single lap joints by ultrasonic and induction welding, exploiting the melting of the thermoplastic film. The joint properties and the chemical compatibility and adhesion of PVB to the carbon fiber-epoxy prepregs were studied by mechanical testing and microstructural analysis

The approach for joining thermosetting matrix composites (TSCs) proposed in this study is based on the use of a low melting co-cured thermoplastic film, added as a last ply in the stacking sequence of the composite laminate. During curing, the thermoplastic film partially penetrates in the first layer of the thermosetting composite, leading to macro-mechanical interlocking as the main connection mechanism between the thermoplastic film and the underlying composite. After curing, the thermosetting composite joints with the thermoplastic modified surface can be assembled by welding. Welding of the TSC-TSC joints is performed by ultrasonic and induction welding. The weld strength is investigated by morphological characterization of cross sections and failure surfaces and by mechanical testing. The effect of the thermoplastic film thickness on the welding process and on its outcome is also analyzed. Both induction and ultrasonic welding mostly result in good-quality welded joints. The welding process used as well as the initial thickness of the thermoplastic film are found to have a significant effect on the final thickness of the weld line and on the location of failure. Thicker thermoplastic films are found to ease the welding processes.

In this work, the behavior of hybrid composite plates, embedding superelastic shape memory alloy (SMA) wires, subjected to low-velocity impacts was studied. The impact experiments were performed on glass reinforced thermoset composite plates containing 1% by volume of superelastic thin wires (0.1 mm of diameter) of a SMA. The specimens were impacted with instrumented drop weight impact equipment: different dropping heights were used to attain impact energies from 1 to 500 J. The shape and size of damaged area were analyzed using two nondestructive inspection methods: (1) light scattering under back illumination was used to observe minor damages such as matrix cracks and fiber matrix debonding and (2) the size and shape of large damages such as delaminations were evaluated by infrared thermography

This work is aimed to study the mechanical properties of basalt fibers, and their adhesion to polypropylene (PP) matrices. Single filament tensile tests were used to calculate the strength of different types of fibers, characterized by different providers and surface treatment. Single fiber fragmentation tests (SFFT) were used to calculate the critical length of the fibers, in a homopolymer PP matrix and in a maleic anhydride modified PP matrix. It was shown that the tensile strength of the fibers is not significantly influenced by the origin or the surface treatment. Only fibers without any sizing show very reduced mechanical properties. On the other hand, the tensile strength was shown to be severely dependent on the filament length. Weibull theory was used in order to calculate the fitting parameters σ0 and β, which were necessary in order to extrapolate the tensile strength to the critical length determined by SFFT. This allowed calculating the adhesion properties of the basalt fibers. It was shown that fiber-matrix adhesion is dependent on both the presence of sizing on the fiber surface, as well as on the modification of the matrix.

In this work, a method developed for the measurement of the transversal permeability of fibrous reinforcement is presented. The permeability of a reinforcement is defined by the Darcy equation and can be obtained once the pressure drop through the reinforcement and the viscosity and average velocity of the fluid are known. The method used in this work is based on a proper modification of a capillary rheometer, obtained by substituting the capillary with a tool, capable of sustaining the reinforcement during reinforcement impregnation and through thickness flow. The developed device was used to measure the pressure built during the flow at different velocities of the rheometer piston. The impregnation tests were performed at different temperatures using a high-viscosity matrix characterized by a Newtonian behaviour. At each temperature, pressure versus velocity plots showed two distinct zones, each characterized by a different slope. The slope observed at low pressures was higher than the slope observed at pressures, suggesting an increase in the permeability with increasing pressure or velocity. The double slope was attributed to the existence of two different impregnation mechanisms, the first one being characteristic of the flow of the matrix around the reinforcement bundles and the second is the characteristic of the flow of the matrix inside each bundle. Dimensionless analysis models and scanning electron micrographs were used to support that the slope of the first portion of the plot is due to inter-bundle flow, whereas the slope of the second portion is due to global flow including both inter- and intra-bundle flow.

Ultrasonic propagation was used to provide heat and pressure in order to perform impregnation and consolidation during production of thermoplastic matrix composites. For this purpose, a new experimental set-up, integrating a laboratory filament winding machine with a horn and a compaction roller, was developed. The heat transfer phenomena occurring during continuous impregnation and consolidation were simulated solving by finite element (FE) analysis the energy balance equations in 2D accounting for the heat generated by ultrasonic waves, the melting characteristics of the matrix and the movement of the thermoplastic commingled roving. The temperature distribution in the composite, predicted by the numerical simulations, was validated by temperature measurements during the production of E-glass/polypropylene cylinders, with the optimized parameters obtained by the FE analysis. The ultrasonic consolidated composite cylinders were characterized by low void content and a shear modulus comparable with that obtained by the micromechanical analysis.

The propagation of low intensity ultrasound in a curing resin, acting as a high frequency oscillatory excitation, has been recently proposed as an ultrasonic dynamic mechanical analysis (UDMA) for cure monitoring. The technique measures sound velocity and attenuation, which are very sensitive to changes in the viscoelastic characteristics of the curing resin, since the velocity is related to the resin storage modulus and density, while the attenuation is related to the energy dissipation and scattering in the curing resin. The paper reviews the results obtained by the authors’ research group in the last decade by means of in-house made ultrasonic set-ups for both contact and air-coupled ultrasonic experiments. The basics of the ultrasonic wave propagation in polymers and examples of measurements of the time-evolution of ultrasonic longitudinal modulus and chemical conversion of different thermosetting resins are presented. The effect of temperature on the cure kinetics, the comparison with rheological, low frequency dynamic mechanical and calorimetric results, and the correlation between ultrasonic modulus and crosslinking density will be also discussed. The paper highlights the reliability of ultrasonic wave propagation for monitoring the physical changes taking place during curing and the potential for online monitoring during polymer and polymer matrix composite processing

The degree of crystallinity of cellulose was used for assessing the degradation level of coated and uncoated samples of pine wood after weathering. X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy measured the changes in the surface crystallinity of cellulose resulting from weathering, both natural and artificial. Both techniques revealed an increase in the crystallinity index (CI) of cellulose when wood was subjected to weathering. An increase in the size of crystallites was also observed by XRD measurements. These results were related to the reduction of the amorphous fractions of wood, and, consequently, to the enrichment of the relative crystalline content. Thanks to FT-IR analysis, the degradation of hemicellulose was observed for uncoated samples after exposure to artificial weathering. The effect of weathering was less evident on coated samples because of the protective action of the coating. A good correlation between the crystallinity indexes obtained from FT-IR and XRD was found. The experimental results proved that the proposed method may be a very useful tool for a rapid and accurate estimation of the degradation level of wood exposed to weathering. This methodology can find application in the field of conservation and restoration of wooden objects or in the industry of wood coatings.

The potential improvement of physical and mechanical properties in nanostructured composites can be fully exploited by proper distribution of the nanofillers in the polymer matrix, which strongly affects both their final properties and processability. A nanofilled thermosetting polymer can be used as a matrix for continuous fibers when the alignment of a high aspect ratio nanofiller is achieved: in this case a hierarchical composite is obtained. In this work a new processing technology for the production of hierarchical polymer based composites is proposed. First, the alignment of graphene nanoplatelets (GNPs) in thermoplastic fibers of amorphous polyetylene terephthalate (PETg) is achieved by a fiber spinning process. The obtained nanocomposite fibers with a very high filler content (10 wt%) are then transferred into a reactive epoxy resin. After dissolution of PETg, the nanofillers remained oriented in the thermosetting matrix. The characterization of the obtained nanocomposites has been carried by means of different experimental techniques which provided complementary results.

The use of polyether polyols is common in the polyurethane (PU) industry, particularly for soft PU applications. In particular, viscoelastic foams, characterized by slow recovery after compression, are obtained using poly(ethylene oxide) (PEO) polyols. Nanofilled polyols can be used for the production of viscoelastic foams with improved fire-resistance properties. The high polarity of polyetherpolyols is responsible for a poor affinitywiththeorganicmodifiersusedincommercialorganicallymodified montmorillonite (omMMT). The aim of the work reported here was the development of a procedure for enhanced polyether polyol intercalation using modified MMT. The exfoliation of the lamellar nanofiller is obtained during the mixing stage of the polyol and the MMT. The MMT is modified using polyetheramines with different amounts of ethylene oxide/propylene oxide. Aftermixingwith the modifiedMMT, the polyol shows an increase in viscosity by three orders of magnitude, and the diffraction angles of the MMT measured by X-ray analysis decrease to values lower than 1.5◦. The intercalated structure is preserved after the curing stage, when isocyanate is added to the polyol/omMMT. The resulting PU has an irregular open-cell structure, and is characterized by a higher flame resistance compared to unfilled PU. Organically modified MMT was prepared, having an improved affinity with polyether polyols. The modified MMT has an improved compatibility with the PEO-based polyether polyols commonly used for soft PU foam production. The properties of the nanofiller can be tailored by varying the type and amount of organicmodifier. A strongly intercalated/exfoliated structure is obtained aftermixing the polyol with the omMMT.

Bioactive food-preserving materials are based on the use of a natural antimicrobial compound loaded in a carrier material, which is able to trigger its release when requested and to modulate the rate of release, thus using either toxic or inhibitory properties against pathogens or bacteria due to food decomposition. In this study, the Schiff base formation for chitosan functionalization was achieved by the reaction of chitosan with cinnamaldehyde at different concentrations. Cinnamaldehyde is an aromatic α,β-unsaturated aldehyde, and the major component in essential oils from some cinnamon species. It has been shown to exert antimicrobial action against a large number of microorganisms including bacteria, yeasts, and mould. The formation of the Schiff base is reversible under suitable conditions, and this might allow the release of the active cinnamaldehyde from chitosan, used as the carrier. The reaction kinetics was investigated by means of rheological measurements, while infrared spectroscopy was used to assess the efficacy of the functionalization. The addition of nanometric graphene stacks to the cinnamaldehyde-functionalized chitosan films was evaluated with the aim to increase the mechanical properties of the film. Finally, the films were tested for antifungal properties with bread slices against a selected mould line.

The impregnation of a glass woven fabric with an amorphous polyethylene terephthalate copolymer (PET-g) matrix was investigated using a finite element (FE) model for interbundle and intrabundle flow of the matrix. Micrographs of samples obtained by film stacking of PET-g to impregnate the glass fabric have confirmed the occurrence of interbundle and intrabundle flow, taking place as separate steps. On the basis of this evidence, two different mechanisms for the fiber impregnation were postulated. The first flow process is associated with a macroscale interbundle impregnation, whereas the second is associated with microscale intrabundle impregnation. Two different FE models were developed to simulate the microscopic and macroscopic flow of the matrix, considering a large number of different random fiber arrangements. Both models could account for the non-Newtonian rheological behavior of the thermoplastic matrix. The microscale impregnation of fibers was simulated by using randomly spaced and nonoverlapping unidirectional filaments. The effect of the number of filaments and the number of random distributions necessary to achieve an adequate accuracy of the method was assessed. The results obtained from the simulation showed that at low pressures, the polymer melt exhibits Newtonian behavior, which makes it possible to predict the tow permeability by the Darcy law. A more difficult situation arises at high pressures because of thenon-Newtonian behavior of the melt. This requires the introduction of a value for the permeability that is also dependent on the rheological properties of the melt. The same non-Newtonian behavior of the matrix was observed for macroscale impregnation of bundles

High power ultrasound was used in order to mould thermoplastic composites in a process including the simultaneous fibers impregnation and plies consolidation. An experimental equipment, made of an ultrasonic device implemented on a filament winding machine, was developed. During winding, a titanium horn is put in contact with thermoplastic layer and its melting point is reached. Several cylindrical speciments were fabricated and their physical, mechanical and morphological properties were investigated. Temperature field obtained during in-situ consolidation through heat generated by ultrasonic waves propagation was modeled using finite element (FE) analysis in order to optimize process parameters

simple procedure for the alignment of graphene nanoplatelets (GNPs) in a thermosetting matrix is presented. First, the alignment of GNPs in thermoplastic fibers of amorphous polyetylene terephthalate (aPET) is achieved by a fiber spinning process. The nanocomposite fibers, obtained with a very high filler content (10 wt%), are then transferred into a reactive epoxy resin. After dissolution of aPET, the nanofillers remained oriented in the thermosetting matrix. The characterization of the obtained nanocomposites has been carried by means of different experimental techniques which provided complementary results. The proposed method has the potential to be used in the manufacturing of hierarchical composites, by introducing nanofilled microfibers into continuous fibers reinforced composites.

The present work is aimed to the preliminary analysis of the applicability of cardanol derivatives as renewable plasticizers for soft PVC. Two different plasticizers were studied, obtained by esterification of the cardanol hydroxyl group (cardanol acetate) and further epoxidation of the side chain double bonds (epoxidated cardanol acetate). Differential Scanning Calorimetry (DSC) was used to study the miscibility between PVC and cardanol derived plasticizers. The miscibility was correlated to the chemical structure of plasticizer by means of the Hansen solubility parameter analysis. Results obtained indicated that esterification of cardanol yields a partial miscibility with PVC, whereas esterification and subsequent epoxidation yield a complete miscibility with PVC. Therefore cardanol acetate, obtained by solvent-free esterification of cardanol, was used as a secondary plasticizer of PVC. Mechanical and rheological analysis showed that the cardanol acetate can partially replace DEHP in PVC formulation.

Transparent nanocomposite films were prepared using bacterial cellulose (BC) as reinforcement and diethylene glycol bis(allyl carbonate) polymer (DEAC) as matrix by vacuum infiltration and UV polymerization. The BC/DEAC nanocomposites exhibit excellent transparency up to 88% at wavelength of 550 nm. The uniform dispersion of resin in BC 3D network was evidenced from SEM and ATR-FTIR analyses, confirms the complete photo-polymerization of diethylene glycol bis(allyl)carbonate monomer to Poly (diethylene glycol bis(allyl carbonate) in BC network. The BC/DEAC composites have good mechanical properties, reaching a tensile strength of 130 MPa and a Young’s Modulus of 6.4 GPa. Applying a micromechanic modeling approach, the elastic modulus of the composite was used in order to determine the average aspect ratio of BC fibers. These flexible transparent BC/DEAC

The present work deals with the development of a biodegradable superabsorbent hydrogel, based on cellulose derivatives, for the optimization of water resources in agriculture, horticulture and, more in general, for instilling a wiser and savvier approach to water consumption. The sorption capability of the proposed hydrogel was firstly assessed, with specific regard to two variables that might play a key role in the soil environment, that is, ionic strength and pH. Moreover, a preliminary evaluation of the hydrogel potential as water reservoir in agriculture was performed by using the hydrogel in experimental greenhouses, for the cultivation of tomatoes. The soil-water retention curve, in the presence of different hydrogel amounts, was also analysed. The preliminary results showed that the material allowed an efficient storage and sustained release of water to the soil and the plant roots. Although further investigations should be performed to completely characterize the interaction between the hydrogel and the soil, such findings suggest that the envisaged use of the hydrogel on a large scale might have a revolutionary impact on the optimization of water resources management in agriculture.

In this work, a finite model able to evaluate the evolution of resin pressure as a function of temperature and degree of reaction, accounting for viscosity changes, during autoclave cure cycles has been developed. The model also includes a kinetic and rheological model whose input parameters have been experimentally determined by Differential Scanning Calorimetry and rheological analysis. The predicted resin pressure for different lay up, including breather thickness, and for different cure cycles has been compared with the results of experimental characterization of void evolution.

The engineering aspects associated with the development of nanocomposites involve either their final properties either their processability. Both are affected by the distribution of nanofiller in the matrix and by the aspect ratio of the nanofiller. A nanofilled thermosetting resin can be exploited as a matrix for continuous fibers when the alignment of a high aspect ratio nanofiller is achieved: in this case a hierarchical composite is obtained. A new procedure for the alignment of nanofillers in a thermosetting matrix is proposed in this study. The two-step approach is based on i) the alignment of nanofillers (carbon nanotubes, graphene, ect.) in thermoplastic fibers by a fiber spinning processes and ii) use of these nanocomposite fibers as a carrier to bring aligned nanofillers into a reactive thermosetting resin. These fibers, soluble in the thermosetting resin, release the nanofillers orientated according to the direction in which fibers are positioned, even after the matrix curing. The proof of concept is demonstrated by producing melt spun polyetylene terephtalate (PETg) fibers filled with graphene nanoplatelets (GNP) and multi-wall carbon nanotubes (MWCNT) with a very high filler content (up to 10 wt%) in view of producing a hierarchical composite

Coupled polymer/composite parts were obtained for adapting a bladder-molding technique, previously developed for the production of hollow components with continuous fiber-reinforced thermoplastic matrix composites. The internal layer (bladder side) is made up of an unreinforced thermoplastic polymer, linear low-density polyethylene (LLDPE), and the external one (mold side) is made up of a thermoplastic matrix composite, based on isotactic polypropylene (PP) and E-glass fabric. The adhesion between the two layers is achieved by applying pressure (<1 bar) through a silicone bladder. The composite/polymer interface was characterized by the evaluation of the interfacial shear strength (IFSS) (between composite and unreinforced polymer), flexural stiffness, and short-beam strength analysis. The experimental mechanical properties were compared with model results, derived on the assumption that perfect adhesion exists between the two layers. A good agreement between predicted and experimental mechanical properties was observed. As indicated by double notch shear tests, used for the IFSS evaluation, good adhesion between LLDPE and PP matrix composite was achieved during processing. The results reported confirm the suitability of the method for a double-layer structure fabrication.

Rapid prototyping techniques have been investigated for the production of biomedical devices that perfectly fit the patient's tissue defect (e.g. for bone and dental applications) and/or reproduce the microstructure of the tissue or organ of interest. The possibility to create patient-specific devices has been recently exploited for the creation of tissue engineer-ing scaffolds, i.e. porous, resorbable matrices, which stimulate cell functions and induce tissue regenera-tion by providing cells with appropriate physical, mechanical and biochemical cues. Poly(ethylene glycol) (PEG)-based hydrogels, although intrinsically non-biodegradable and non-bioactive, show great promise as tissue engineering scaffolds, due to their ability to be covalently linked to bioactive and/or degradable moieties, that elicit specific cell responses, and to their fast and biocompatible formation under ultra-violet (UV) exposure. In this work, poly(ethylene glycol)-based hydrogels, containing bioactive moieties, were photopolymerized and characterized in terms of mechanical, swelling and degradation properties. The production of hydrogels possessing a complex shape was finally investigated by means of stereolithography, a rapid prototyping technique which is able to build a three-dimensional object, starting from the CAD model, by guiding an ultravio-let laser beam on the surface of a photosensitive solution. The results demonstrated that the developed hydrogel formulations allow the creation of biomimetic constructs with complex shapes, which might be useful as platforms for tissue engineering or as tissue mimicking phantoms.

A finite element (FE) model able to evaluate both the evolution of resin flow, degree of reaction and void formation during autoclave cure cycles was developed. The model was implemented using a commercial epoxy matrix widely used in aeronautic field. The FE model also included a kinetic and rheological model whose input parameters were experimentally determined by Differential Scanning Calorimetry and rheological analysis. The FE model was able to predict the evolution of degree of reaction with very good agreement with the experimental data. Moreover, the predicted resin losses were lower than 3% of the overall composite resin content.

During autoclave processing of composites for high-performance applications, it is mandatory to limit the porosities, which mainly depend on the hydrostatic pressure in the resin. This pressure, which is not constant during heating being affected either by resin flow either by elastic stress in the fiber stack, can be significantly different from the autoclave pressure. Modeling of resin flow and stress in the fiber stack is a key issue for prediction of the resin hydrostatic pressure, which can be related to void development. Also, the viscosity of the thermosetting matrix is a relevant parameter since it is not constant but evolves during curing going through a minimum and then increasing to an infinite value at gel point. In this work, a viscoelastic model is adopted to calculate the evolution of resin pressure during an autoclave cycle up to gelation, accounting for viscosity and degree of reaction changes. Therefore, the model includes a kinetic and rheological model whose input parameters have been experimentally determined by Differential Scanning Calorimetry and rheological analysis. The predicted resin pressure for three case studies associated to different composite and bleeder thicknesses and reinforcement materials have been discussed

This paper is aimed to study the suitability of bio-polymers, including poly-lactic acid (PLLA) and Mater-Bi, for the production of hollow components by rotational molding. In order to reduce the brittleness of PLLA, the material was mixed with two different plasticizers, bis-ethyl-hexyl-phthalate (DEHP) and poly-ethylene-glycol (PEG). The materials were characterized in terms of sinterability. To this purpose, thermomechanical (TMA) analysis was performed at different heating rates, in order to identify the endset temperatures of densification and the onset temperatures of degradation. Results obtained indicated that the materials are characterized by a very fast sintering process, occurring just above the melting temperature, and an adequately high onset of degradation. The difference between the onset of degradation and the endset of sintering, defined as the processing window of the polymer, is sufficiently wide, indicating that the polymers can be efficiently processed by rotational molding. Therefore, a laboratory scale apparatus was used for the production of PLLA and Mater-Bi prototypes. The materials were processed using very similar conditions to those used for LLDPE. The production of void-free samples of uniform wall thickness was considered as an indication of the potentiality of the process for the production of biodegradable containers

This work is aimed to study the suitability of the wooden backbone of opuntia ficus indica cladodes as reinforcement for the production of biodegradable composites by rotational molding. The wooden backbone is extracted from opuntia ficus indica cladodes, which constitute a very relevant agricultural scrap, and is characterized by a thick-walled cellular structure. In view of the potential of poly-lactic acid (PLA) for the production of hollow components by rotational molding, the use of the wooden backbone is expected to increase the stiffness of the material. The wooden backbone of opuntia cladodes can be readily incorporated in the wall thickness of rotational molding products, in contrast to other natural fibers in the form of filaments and/or bundles, which are very difficult to use in the rotational molding. The results obtained showed that, although being characterized by lower properties compared with compression-molded PLA, the bio-composites are characterized by adequate mechanical properties, higher than those previously found for PLA processed by rotational molding. In view of a potential application for the production of fully biodegradable hollow parts, an increase of stiffness and strength can therefore be attained adopting materials and procedure developed in this work.

This paper is aimed at studying the effect of the grade and the granulometry of poly(lactic acid) (PLA) on its processability by rotational molding. Two PLA grades were considered: a low melt flow rate (MFR), high viscosity, material, characterized by an excellent quenchability, leading to a completely amorphous structure of rotomolded samples; a high MFR, low viscosity, material, characterized by a lower quenchability, leading to a semicrystalline structure of rotomolded samples. Three different granulometries were considered: a coarser one, that is, the pellets as received, intermediate size pellets produced by extrusion followed by pelletizing, and a powder obtained by grinding of as received pellets. Besides the different dimensions, the intermediate size pellets also experienced a supplementary extrusion step, which induced some degradation in the material. For both grades and three granulometries, void-free prototypes were obtained, which indicate a very efficient sintering process, attributed to the low viscosity of all PLA grades. As a consequence, the modulus of the rotomolded samples was found to be unaffected by the PLA grade or granulometry. In contrast, the strength was shown to be more significantly dependent on quenchability than on the grade. To obtain an adequately high strength, an amorphous structure must be developed during cooling. Finally, the supplementary extrusion step experienced by the intermediate size pellets was shown to significantly decrease the strength of prototypes, as a consequence of the thermal degradation induced by this additional processing step.

The aim of this work was to develop polyamide-6/ organic-modified montmorillonite (omMMT) nanocomposites for the production of hollow parts by rotational molding. Particular emphasis was placed on the mechanical and flame retardancy properties needed for the fabrication of vessels for flammable liquids. The morphology of the melt compounded nanocomposites, produced by melt compounding, was investigated by X-ray diffraction measurements (WAXD), and Transmission Electron Microscopy (TEM) showed an exfoliated structure. Rheological measurements were used in order to verify whether the viscosity of materials was adequate for rotational molding. While thermomechanical analysis has revealed that neat PA6 and its nanocomposites were not suitable for rotational molding, due to the very low thermal stability of the polymer, the addition of a thermal stabilizer, shifted the onset of degradation to higher temperatures, thus widening the processing window of both PA6 and PA6 nanocomposites. Large-scale vessel prototypes were obtained by rotational molding of thermo-stabilized PA6 and its nanocomposites, and samples extracted from the rotomolded parts were characterized with respect to physical and mechanical properties. It was found that the PA6 nanocomposites exhibited significant improvements at cone calorimeter tests in comparison with neat PA6.

The aim of this paper is the production of fiber reinforced LLDPE components by rotational molding. To this purpose, a process upgrade was developed, for the incorporation of pultruded tapes in the rotational molding cycle. Pultruded tapes, made of 50% by weight of glass fibers dispersed in a high density polyethylene(HDPE) matrix, were glued on the internal surface of a cubic mold, and rotational molding process was run using the same processing conditions used for conventional LLDPE processing. During processing, melting of LLDPE powders and of HDPE allowed to incorporate the tapes inside rotational molded LLDPE. The glass fiber reinforced prototypes were characterized in terms of mechanical properties. Plate bending tests were performed on the square faces extracted from the rotational molded product. The rotational molding products were also subjected to internal hydrostatic pressure tests up to 10 bar. In any case, no failure of the cubic samples was observed. In both cases, it was found that addition of a single pultruded strips, which corresponds to addition of about 0.6% by weight of glass fibers, involved an increase of the stiffness of the faces by about 25%.

This work is aimed to study the use of pultruded profiles for the selective reinforcement of linear low density polyethylene (LLDPE) parts produced by rotational molding. A preliminary screening on different types of pultruded profiles was performed, highlighting the relevance of adhesion to LLDPE in order to prevent debonding of the reinforcing pultruded profiles. As expected, high density polyethylene (HDPE) matrix pultruded tapes are characterized by a very high adhesion to rotomolded LLDPE. Therefore, HDPE matrix pultruded tapes, fastened on the inner surface of the mold, are incorporated into LLDPE during rotomolding. Plate bending tests performed on reinforced rotomolded plates and pressurization tests performed on the box shaped prototypes showed a significant increase of the stiffness with a negligible amount of reinforcement and increase of the weight of the component.

The use of fabrics with antibacterial properties for commodity applications can provide numerous advantages such as a reduction in the release of odors due to bacterial proliferation in sweat and a reduction in the development of skin hypersensitivity reactions due to microorganisms trapped into the fabrics. Silver is one of the most effective antibacterial agents used for the high degree of biocompatibility and for its long-term antibacterial effectiveness against many different bacterial strains. In this study, an innovative technique for the deposition of nanosilver antibacterial coating on woolen fiber was analyzed. In particular, fabrics woven with different percentages of silver-treated fibers were compared to determine the best ratio preserving the antibacterial activity and optimizing the cost-effectiveness of the final product. Scanning electron microscopy revealed a uniform distribution of silver nanoclusters on the fibers. The impressive silver coating stability and durability were demonstrated after several washing cycles through thermogravimetric analysis. The antimicrobial activity of the silver-treated substrates was evaluated by antibacterial tests on Escherichia coli. A very strong antibacterial activity was found even in presence of the lower silver content; therefore, a blend of coated and uncoated fibers is proposed for practical applications.

This paper is aimed to study the suitability of poly-lactic acid (PLLA) for the production of components by rotational molding. To this purpose, the sintering behavior of PLLA powders was studied by thermomechanical analysis (TMA), in order to identify the onset and endset temperatures of sintering and the onset temperatures of degradation. The results indicate that sintering of PLLA is characterized by two different steps, namely powder coalescence and void removal. The first process is fast, occurring just above the melting temperature, whereas the second one occurs at much higher temperatures. Finally, at higher temperatures, degradation involves the formation of gas in the bulk of the polymer, leading to a decrease of the bulk density. The different phenomena occurring during heating of PLLA powders were interpreted by means of dimensionless numbers. The use of such approach allowed identifying the processing window for PLLA powders, defined as the difference between the endset of sintering and the onset of degradation. In agreement with experimental results, the dimensionless analysis confirmed that wider processing windows are obtained for slower heating rates of PLLA powders. On the other hand, it is well known that potential materials for rotational molding should be characterized by an adequate toughness, essentially related to de-molding of parts. Therefore, PLLA was mixed with two different plasticizers, a non-biodegradable one, i.e. di-ethyl-hexyl-phthalate (DEHP) and a biodegradable one, i.e. poly-ethylene glycol (PEG). The plasticizers were responsible of a reduction of viscosity and therefore a faster sintering process. On the other hand, the decrease of thermal stability due to the addition of plasticizer is expected to significantly decrease the width of the processing window.

A durable and flexible silicone-based backcoating (halogen free) is applied to the backside of an otherwise smoldering-prone and flammable fabric. When exposed to fire, cyclic siloxanes (produced by thermal decomposition of the backcoating) diffuse through the fabric in the gas phase. The following oxidation of the cyclic siloxanes forms a highly conformal and thermally stable coating that fully embeds all individual fibers and shields them from heat and oxidation. As a result, the combustion of the fabric is prevented. This is a novel fire retardant mechanism that discloses a powerful approach towards textiles and multifunctional flexible materials with combined smoldering/flaming ignition resistance and fire-barrier properties.

This work was aimed to test the suitability of an epoxidized cardanol derived plasticizer for the production of soft PVC characterized by low environmental and toxicological impact soft PVC. Nowadays, the use of natural derived plasticizer in soft PVC industry is emerging as valid alternative towards conventional phthalate plasticizers, in order to reduce the environmental and toxicological impact of soft PVC. In facts, cardanol is a natural and renewable resource, characterized by a wide worldwide availability. In addition, being derived from cashew nut shell liquid, which is a by-product of cashew nut shell industry, it does not contribute to the subtraction of resources from the food chain, in contrast, for example, to epoxidized soybean oil. To this purpose, soft PVC samples were produced in an industrial plant, using both cardanol derived and phthalate plasticizer. Thermal and mechanical characterization showed that the properties of PVC plasticized by cardanol derivative are comparable to those of soft PVC obtained by phthalate, which is a clear indication of the good plasticizing effectiveness of cardanol derivative, and highlights its potential for the production of soft PVC characterized by reduced environmental and toxicological impact.

The structural behaviour of bolted joints of composite laminates for aerospace applications was modelled comparing the shape, amplitude and phase of stress–strain cycles. This study proposes a model for the bolted joints resulting in a typical load–displacement curve, under cyclic loading, significantly affected by hysteretic effects. From the data gathered through the experimental activities, a constitutive relationship between strain and stress was proposed, starting from simple physical models. The assumption of a rigid shift between the laminates was used to correlate load and displacement curves in the different phases of the load cycle. The hysteretic behaviour was attributed to friction phenomena and interpreted using damping coefficients characterizing the global dynamic response of the structural joint.

Polymer nanocomposites are usually studied by means of different techniques, being wide angle X - ray diffraction (WAXD) and transmission electron microscopy (TEM) the most commonly used. Although WAXD offers a convenient method to determine the interlayer spacing of the silicate layers in the intercalated nanocomposites, little can be said about the spatial distribution of the silicate layers or any structural non-homogeneities in nanocomposites. On the other hand, TEM is very time-intensive, and only gives qualitative information on the sample as a whole, due to the small investigable area [ ]. In this work, PETg nanocomposites were produced by melt intercalation of omMMT at different temperatures. Nanocomposites were characterized by means of WAXD and TEM analysis, showing that XRD is only able to capture some of the basic features of the nanocomposite morphology. Further, DSC analysis revealed the relevance of the degree of intercalation on the relaxation times of the nanocomposite.

The improvement of physical and mechanical properties of nanofilled matrices significantly depends on the average size of dispersed fillers. In particular, the aspect ratio of lamellar nanofillers, such as graphene stacks, results from a combination of both filler morphology and processing techniques. In this study, nanocomposites were obtained dispersing three different graphene precursors in an epoxy resin: expanded graphite, commercial graphene nanoplatelets, and natural graphite. Epoxy matrix nanocomposites reinforced with graphene stacks, ranging from 1 wt% to 3 wt% were prepared and characterized. The structural, mechanical, and thermal properties of expanded graphitebased nanocomposites, as well as the rheological properties of liquid resin/filler suspensions, were studied and compared with those of the unfilled epoxy matrix and of the matrix filled with natural graphite and commercial nanoplatelets. The comparison of mechanical and rheological properties with simple mathematical models indicated that the aspect ratio of expanded graphite is in the order of 1000, i.e., a dispersion of nanoscale graphene stacks was obtained. This result suggests that the measurement of engineering properties of nanocomposites not only represents an objective but can also provide information about the average degree of dispersion.

The engineering aspects associated with nanocomposite development are strongly dependent on the final properties that can be achieved as well as on their processability. Both features are affected by the average distribution of nanofiller in the matrix, or in other words by its dispersion. Furthermore, characterization of intercalation or exfoliation of organic modified montmorillonite (omMMT) or graphene lamellae by X-ray or transmission electron microscopy cannot be easily related to nanocomposite macroscopic properties (mechanical, rheological etc.), the most relevant from an engineering point of view. On the other hand mechanical and rheological analysis shows that properties of nanocomposites are not only dependent from lamellar spacing but also the aspect ratio plays a key role. Even if single graphene sheets or single omMMT are not observed in the matrix bulk, a high aspect ratio of the filler can generate a significant improvement of macroscopic properties. Finally, the measurements of engineering properties of nanocomposites not only represent an objective but can provide information about the average degree of dispersion. Comparison of mechanical and rheological properties with simple mathematical models can be used to determine the average aspect ratio of nanofillers. It may be concluded that macrocharacterization can represent a valuable and complementary tool for the morphological characterization of nanocomposites being capable of providing information about the level of dispersion of nanocomposites.

The aim of this study is the characterization of recycled carbon fibres, in view of their potential application in long-fibre reinforced thermoplastic composite. The fibres were obtained from epoxy matrix composite panels, applying a patented process that includes the pyrolisis of the matrix followed by an upgrading of the fibres. Then, recycled fibres were further subjected to thermal and acid treatments in order to modify their surface morphology and chemistry. Scanning electron microscopy and energy dispersive spectrometry were used to characterize the morphological and compositional changes of the fibre surface. The fibres were characterized in terms of mechanical properties and adhesion to an epoxy matrix. The fibres treated by thermal processes at high temperatures (600C) were shown to be too severely damaged, making them unsuitable for the production of fibre-reinforced composites. A thermal treatment at lower temperatures (450C) involved a very limited damaging without any evident chemical modification of the fibre surface, which in turn involved a limited increase of the adhesion properties to an epoxy matrix. Chemical treatment by nitric acid caused a very limited damage of fibres, coupled with a significant modification of surface chemistry, which in turn involved a further increase of the fibre/matrix adhesion properties.

In this study nanocomposites were prepared by dispersing three different grades of graphite particles, expanded graphite, commercial graphene nanoplatelets and natural graphite, in a commercial epoxy matrix. Dielectric properties, thermal conductivity and permeability to oxygen of the composites were studied and compared to those of the unfilled epoxy matrix. An increase of all properties is obtained using expanded graphite, suggesting the presence of a good dispersion of the filler in the matrix and a strong polar interactions of the filler with the matrix, attributed to the partially oxidised surfaces of the expanded graphite. All the measured transport properties were fitted with simple mathematical models obtaining good agreement between the experimental results and theoretical predictions. The model parameters were related to the aspect ratio of the filler, defined as the ratio between the in-plane average dimension and the thickness of the reinforcement. An aspect ratio between 1250 and 1550 indicates that graphite thin platelets (or graphene stacks), characterized by a thickness of the order of a few tens of nanometers, were dispersed in the epoxy matrix.

In this work, a new FE model was developed, in order to simulate the diffusion into polymer nanocomposites in 2D and 3D geometries. The simulation model is based on a random distribution of non-interpenetrating impermeable lamellae with an arbitrary average orientation angle. Simulations were run at different filler volume fractions, aspect ratio and orientation angles. Simulation results showed that the normalized coefficient of diffusion only depends on the normalized path length, which is, in turn, dependent on the morphology of the composite (volume fraction, aspect ratio and orientation). The dependency of the normalized coefficient of diffusion on normalized path length was found to follow a simple power law model. In order to account for the normalized path length dependence on filler volume fraction and aspect ratio, a geometrical model was developed, which is based on the probability of collision of diffusing particles on the lamellar surface. For a random orientation of particles, both in 2D and 3D geometries, the developed model showed an excellent agreement with the simulation results. In 3D, the model prediction are even better than the Bharadwaj model prediction.

We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100–200 keV/c) for particle momenta in a range (50–100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN- Lecce .

Thermoplastic matrix composites are finding new applications in different industrial area, thanks to their intrinsic advantages related to environmental compatibility and processability. The approach presented in this work consists in the development of a technology for the simultaneous deposition and consolidation of commingled thermoplastic rovings through to the application of high energy ultrasound. An experimental equipment, integrating both fiber impregnation and ply consolidation in a single process, has been designed and tested. It is made of an ultrasonic welder, whose titanium sonotrode is integrated on a filament winding machine. During winding, the commingled roving is at the same time in contact with the mandrel and the horn. The intermolecular friction generated by ultrasound is able to melt the thermoplastic matrix and impregnate the reinforcement fibers. The heat transfer phenomena occurring during the in situ consolidation have been simulated solving by finite element (FE) analysis, an energy balance accounting for the heat generated by ultrasonic waves and the melting characteristics of the matrix. To this aim, a calorimetric characterization of the thermoplastic matrix has been carried out to obtain the input parameters for the model. The FE analysis has enabled to predict the temperature distribution in the composite during heating and cooling. The simulation results have been validated by the measurement of the temperature evolution during ultrasonic consolidation. The reliability of the developed consolidation equipment has been proved by producing hoop wound cylinder prototypes using commingled continuous E-glass rovings and polypropylene filaments. The consolidated composite cylinders are characterized by high mechanical properties, with values comparable with the theoretical ones predicted by the micromechanical analysis.

An experimental set-up for the ultrasonic consolidation of commingled thermoplastic rovings has been developed. It integrates a laboratory filament winding machine with the sonotrode of an ultrasonic welding head. A commingled roving made of polypropylene and glass fibers was used to fabricate several prototypes of cylinders of different thicknesses. The physical, mechanical and morphological properties of consolidated composite specimens were measured and related to the different processing conditions. The heat transfer phenomena which occur during consolidation of these rovings were simulated solving, by finite element analysis, the energy balance accounting for the heat generated by ultrasound and the melting characteristics of the thermoplastic matrix

An experimental set-up for ultrasonic cure monitoring has been developed at the Laboratory of Composite Materials (University of Salento). The obtained results demonstrate that ultrasonic wave propagation is able to detect and monitor the physical changes taking place during curing of thermosetting matrices. Moreover, the set-up has the potential for online monitoring during composite processing

The mechanical and electrochemical behavior of ultrasonic spot welded hybrid joints, made of AA5754 aluminum and carbon fiber reinforced epoxy with a co-cured thermoplastic surface layer, was studied. The effect of the welding parameters (energy and force) and the thickness of a thermoplastic film, applied as an upper ply in the composite lay-up, on the development of adhesion strength, was investigated. The best mechanical results were obtained when the welding parameters were able to achieve a large bonding area of mechanical interlocking between naked carbon fibers and aluminum and a better load distribution. The electrochemical results excluded the possibility of galvanic corrosion between aluminum and composite adherends thanks to the insulating action provided by the thermoplastic film

The finite element method (FEM) has been applied to simulate the ultrasonic wave propagation in a multilayered transducer, expressly designed for high-frequency dynamic mechanical analysis of polymers. The FEM model includes an electro-acoustic (active element) and some acoustic (passive elements) transmission lines. The simulation of the acoustic propagation accounts for the interaction between the piezoceramic and the materials in the buffer rod and backing, and the coupling between the electric and mechanical properties of the piezoelectric material. As a result of the simulations, the geometry and size of the modelled ultrasonic transducer has been optimized and used for the realization of a prototype transducer for cure monitoring. The transducer performance has been validated by measuring the velocity changes during the polymerization of a thermosetting matrix of composite materials.

This work is aimed to study the suitability of cardanol derivatives as plasticizers for poly(vinyl chloride), (PVC). The plasticizers are obtained by chemical modification of cardanol, a natural, renewable resource, obtained as a by-product of the cashew nut shell industry. Due to the choice of environmentally friendly chemical modification routes, partial conversion of cardanol to the target compounds was obtained. Consequently, the tested plasticizers were composed of a mixture of different cardanol derivatives. Rheological tests on PVC plastisols obtained with neat cardanol showed that cardanol must be subjected to chemical modifications, such as acetylation and epoxidation, in order to perform as an effective plasticizer. In particular, only after epoxidation, does the cardanol derivative become fully soluble in PVC. PVC plastisols obtained with such cardanol derivatives present a similar gelation temperature compared to bis (2-ethylhexyl) phthalate (DEHP) based plastisols. Mechanical properties of the flexible PVC produced by the addition of cardanol derived plasticizer after epoxidation are also comparable to those attained by the use of DEHP. Nevertheless ageing tests showed an accelerated migration of cardanol derived plasticizer, attributed to the loss of unreacted cardanol present in the plasticizer, which was in turn responsible for a significantly faster degradation of the properties, compared to flexible PVC containing DEHP. This highlights the relevance of achieving a high yield of the acetylation and epoxidation reactions, which is a relevant issue of the future research and development activities in this field.

Non-Destructive Testing of aircraft structures is of paramount relevance leading to key information regarding the structural characteristics and the residual life of a component. This paper is focused on the experimental and modeling activities related to vibrational analysis carried out on a typical aeronautical composite sample. A flap section of a regional aircraft has been studied applying the conventional tools of the modal analysis. The aeronautical component has been at first characterized in terms of natural frequencies and normal modes. Then it has been damaged using a drop tower that induced a controlled impact in the structural component. The vibrational analyses have been repeated and the normal modes in the two conditions have been compared. Then other approaches based on vibrational properties of the structures have been investigated to detect defect and damage.

In this work nanocomposites based on amorphous poly(ethylene terephthalate) (PETg) were developed using melt intercalation. X-ray analysis performed on the PETg nanocomposites showed that intercalation and exfoliation took place during static mixing. The water vapor permeability of PETg nanocomposites was correlated to the volume fraction of the impermeable inorganic part of the omMMT.

L’invenzione propone un metodo per la produzione di un materiale composito fibro-rinforzato consolidato mediante il trattamento tramite energia ultrasonora di un substrato grezzo di tipo commingled, costituito da fibre di rinforzo secche e fibre di matrice polimerica termoplastica (Figura 1). Tramite il trattamento ultrasonoro si ottengono in un'unica operazione le fasi di rammollimento e/o fusione delle fibre di matrice termoplastica, le fasi di impregnazione delle fibre di rinforzo secche e le fasi di consolidamento del composito finale solitamente eseguite, secondo lo stato della tecnica nota, separatamente e secondo fasi successive.

An induction welding method of two adherends (10, 11) at least one of which comprises an electrically conducting composite material having a thermosetting matrix and an interface material (4) comprising a layer of thermoplastic material diffused in the thermosetting matrix and defining a contact surface (S), comprises the steps of:- arranging the contact surface (S) of an adherend (10) onto a thermoplastic material of the other adherend (11);- energizing a coil (12) facing a surface (R) of one of the adherends (10, 11) so as to heat the interface material (4) to a first temperature;- controlling the cooling of the surface (R) so that a second temperature of the surface (R) is lower than the first temperature while the coil (12) is energized.

Production of natural or synthetic yarns with heat transmission barrier property, obtained by deposition of non-hypercritical synthesized aerogel. Characterized by high porosity, the aerogel confers to the yarn thermal insulation properties. This enables the production of fabrics which can be utilized, as an example, under hot and cold extreme conditions. The invention is characterized by a new technique of aerogel non-hypercritical synthesis and by a process of aerogel deposition by impregnation and then yarn exposition to the UV-rays.

Production of yarns able to absorb the sweat, by introduction of super absorbent material (hydrogel) inside the yarn itself, and eventually to release perfume, previously absorbed inside the hydrogel. The super absorbent hydrogel are reticulated polymers, able to absorb up to 2 litre of water per gram of dry material. Production of yarns able to absorb the sweat, by introduction of super absorbent material (hydrogel) inside the yarn itself, and eventually to release perfume, previously absorbed inside the hydrogel. Hydrogel sweat absorption increases the comfort, since the sportsman hangover sensation is often due to the sweat direct contact with the skin. Once washed and dried, the fabric realized with such a yarn is ready for reuse, because the hydrogel absorption characteristics are fully reversible and remain even after the washing. Moreover the hydrogel is able to absorb the perfume of the washing soap and, thanks to its nature, to keep it for a long time and to release it slowly.

A method for the production of components made of ceramic- matrix composite material, in the energy sector (burners, refractory shields for combustion chambers, parts for ovens and heating systems subject to thermal shock and high temperatures, with the need to support heavy mechanical loads), in the metal -casting industry (tubes for conveying molten metal), and in the space sector (thermal shields for re-entry vehicles); according to the method, a preform (6) for ceramic fibres is shaped and set in a draining mould (12), for example made of gypsum; the fibres of the preform (6) are impregnated with a suspension of ceramic powders, the liquid of which is drained by capillarity from the draining mould; simultaneously to draining, a suspension of ceramic powders (20) is infiltrated between the fibres of the preform (6) so as to fill the empty space left by the drained liquid; at the end of the steps of draining/ infiltration a body (21) is obtained with a solidified or compacted porous matrix, which is removed from the draining mould (12) and undergoes sintering.

Production of yarns able to absorb the sweat, by introduction of super absorbent material (hydrogel) inside the yarn itself, and eventually to release perfume, previously absorbed inside the hydrogel. The super absorbent hydrogel are reticulated polymers, able to absorb up to 2 litre of water per gram of dry material. Production of yarns able to absorb the sweat, by introduction of super absorbent material (hydrogel) inside the yarn itself, and eventually to release perfume, previously absorbed inside the hydrogel. Hydrogel sweat absorption increases the comfort, since the sportsman hangover sensation is often due to the sweat direct contact with the skin. Once washed and dried, the fabric realized with such a yarn is ready for reuse, because the hydrogel absorption characteristics are fully reversible and remain even after the washing. Moreover the hydrogel is able to absorb the perfume of the washing soap and, thanks to its nature, to keep it for a long time and to release it slowly.

Una delle più idonee tecnologie per la produzione di corpi cavi in composito è la tecnologia del filament winding. Mentre tra le tenologie per la produzione di corpi cavi in materiale polimerico ci sono il blow-moulding (soffiaggio) e lo stampaggio rotazionale. La tecnologia filament winding permette di produrre pezzi in composito di 5 grandi dimensioni con l’unica limitazione sulle dimensioni del mandrino, per il quale deve essere garantita una adeguata rigidezza. Questa tecnologia permette la produzione di oggetti che hanno una simmetria assiale con l’asse di rotazione.

La società ha per obiettivo primario la valorizzazione dei risultati della ricerca svolta all'interno dell'Università attraverso lo sviluppo di nuovi prodotti e servizi nel campo dei sistemi di monitoraggio, misura e controllo, di sensoristica e di sistemi ed apparati elettrici ed elettronici, con principale riferimento alle applicazioni di interesse sia pubblico che privato. in particolare, si valorizzeranno i risultati della ricerca sviluppata presso l'Università del Salento nel settore delle misure elettriche ed elettroniche, dei campi elettromagnetici, della sensoristica applicata e dei sistemi elettrici ed elettronici.

La società si propone come impresa ad elevato contenuto tecnologico avente per obiettivo primario la valorizzazione dei risultati della ricerca svolta all'interno dell' Università attraverso lo sviluppo di nuovi prodotti e servizi nei campi biomateriali/biotecnologie e salute dell'uomo. In particolare: produzione e commercializzazione di polimeri naturali estratto da tessuti di origine animale; produzione e commercializzazione di dispositivi innovativi ad elevato grado di complessità strutturale a base di tali materiali, sviluppo e prototipazione di nuovi prodotti legati alle terapie avanzate; applicazione industriale di tecniche e tecnologie basate sui processi di sintesi dei materiali e dei dispositivi sviluppati; ricerca, sperimentazione, produzione e commercializzazione nei settori biomedico, cosmetico e farmaceutico.