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.

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.

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

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.

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.

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 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.

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.

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.

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.

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 aim of this work was to study the effect of nanofillers on the structural relaxation phenomena occurring in amorphous poly(ethylene-terephthalate)/poly(cyclohexane-dimethanol terephthalate) copolymer (PET/PCHDMT) nanocomposites in correspondence with the glass transition temperature. PET/PCHDMT nanocomposites were prepared by melt mixing with an organicmodified montmorillonite at different processing temperatures. Differential scanning calorimetry analysis revealed that addition of the organic modifier alone causes a decrease of the glass transition temperature and an increase of the specific heat discontinuity. Nanocomposites showed a higher glass transition temperature and a lower specific heat discontinuity compared with samples obtained by adding organic modifier to PET/PCHDMT. Both effects were more relevant for samples processed at lower temperatures. Therefore, the glass transition temperature was studied by introducing the concept of fictive temperature and relaxation time. It was found that nanocomposites have a higher apparent activation energy and an increased size of cooperatively rearranging regions compared with neat PET/PCHDMT. Both effects are more relevant for nanocomposites processed at lower temperatures. All the discussed effects are explained by considering the enhanced confinement of PET/PCHDMT macromolecules, due to the presence of intercalated lamellae of organofiller. The efficiency of intercalation is increased by decreased processing temperature, which involves an increase of the nano-confinement area of the polymer.

The research aims to investigate the effects of natural and accelerated weathering on polyethylene-based films. At this regard, monolayer films of low density/linear low density polyethylene blends, containing commercially available organic pigments and an UV absorber of the benzophenone type, have been considered. The samples were weathered on field (natural weathering) or using two different artificial procedures: UV lamp and QUV chamber. Conditioned film samples were, then, analyzed by performing several physical tests taking as-received films as a reference. Rheological measurements showed an increase in viscosity of weathered sample melts as a consequence of photodegradation phenomena, inducing the formation of double bonds and crosslinks. This latter result was also confirmed by gel content measurements. UV-visible spectroscopic tests indicated that in both cases of natural and artificial weathering an increase of the transmittance of films occurred. Tensile tests indicated the increase of films stiffness, especially in case of samples conditioned using the UV lamp, and a large decrease of the strain at break, both in machine and in transverse directions, especially for film weathered using the QUV chamber.

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.

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.

In this work, FE analysis was used to study steady-state diffusion into 2 D polymer nanocomposites. The developed FE model is made of randomly distributed and randomly oriented permeable lamellar stacks made of a certain number of platelets, separated by galleries. The model is able to account for diffusion occurring between lamellar stacks, as well as within stacks, inside lamellar galleries. This allows to account for different morphologic features of the nanofiller, including the number of lamellae in each stack, which defines the degree of dispersion, and the lamellar gallery thickness, indicative of the degree of intercalation. 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 nanocomposite. Besides the aspect ratio and volume fraction of the nanofiller, also the degree of intercalation and the degree of dispersion play a significant role in determining the barrier properties of nanocomposites. The behavior of nanocomposites made of permeable lamellar stacks was represented by introducing a geometrical model, which is based on the probability of collision of diffusing particles on the lamellar surface. For a random orientation of lamellar stacks, the developed model showed an excellent agreement with the simulation results. The developed model also allowed to estimate the error arising from the assumption of impermeable stacks when using permeability data in order to calculate the aspect ratio of nanofillers.

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

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.

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.

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.

In this work, diffusion in oriented lamellar nanocomposites was studied by means of FEM analysis. The developed FEM model, based on a random distribution of non-interpenetrating impermeable lamellae with arbitrary orientation, was used to calculate the coefficient of diffusion in lamellar nanocomposites in 3D and in 2D diffusion, at different values of filler volume fractions, aspect ratio and orientation angles. Comparison between coefficient of diffusion obtained by simulation results and Bharadwaj model showed a good agreement. Nevertheless, it was found that the good agreement derives from two counteracting errors, balancing their effect: overestimation of the diffusion length and underestimation of the dependence of normalized diffusion coefficient upon normalized diffusion length. Therefore, in order to gain a better understanding of the diffusion in lamellar nanocomposites, an analytical model was developed, which is able to predict the evolution of coefficient of diffusion as a function of orientation, volume fraction and aspect ratio of the nanofiller. The comparison between the simulation results and analytical model showed a very good agreement, comparable to that found for the Bharadwaj model. In addition, the developed analytical model provided an excellently good estimation of the diffusion length.

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.

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.

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 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 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.

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.

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.

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.