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In this work, highly filled composites made of a commercial polypropylene resin and low melting point Tin particles, up to 50 vol.% in loadings, have been prepared by melt blending process. The introduction of stearic acid (SA), a common dispersant, was investigated in compositions. The developed systems were characterized in terms of dynamic rheological testing. Final results confirmed a reduction of linear viscoelastic domain, by increasing filler loadings, with an effect more emphasized in the presence of SA. Contrary to literature studies, at equal filler content (50%), both moduli resulted to be superior for formulations containing the dispersing agent. A further rheological characterization continued on systems at 30 vol.% of particle loadings for highlighting differences depending on the SA addition. Specific tests were also performed at temperatures above the melting of Tin particles. Finally, optical microscopic analyses were carried out for gaining insight on sample microstructure, in controlled conditions of temperature and shear rate.

The global production of plastic is increasing, and plastic represents one of the most popular materials, widespread in countless applications in commercial and industrial fields and everyday life [...]

The purpose of this study is to limit the environmental impact of packaging applications by promoting the recycling of waste products and the use of sustainable materials in additive manufacturing technology. To this end, a commercial polylactide acid (PLA)-based filament derived from waste production of bio-bags is herein considered. For reference, a filament using virgin PLA and one using a wood-based biocomposite were characterized as well. Preliminary testing involved infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The effect of printing parameters (namely bed temperature, layer thickness, top surface layers, retraction speed, and distance) on the final aesthetics of 3D printed parts was verified. The results allow us to attest that the thermal properties of recycled polymer are comparable to those of virgin PLA and biocomposite. In the case of recycled polymer, after the extrusion temperature, bed temperature, and printing speed are estabilished the lowest allowable layer thickness and an appropriate choice of retraction movements are required in order to realize 3D-printed objects without morphological defects visible to the naked eyes. In the case of wood biocomposite, the printing process was complicated by frequent obstructions, and in none of the operating conditions was it possible to obtain an aesthetically satisfying piece of the chosen geometry (Lego-type bricks) Finally, mechanical testing on the 3D printed parts of each system showed that the recycled PLA behaves similarly to virgin and wood/PLA filaments.

This work aimed to review the recent scientific research, focused on the application of recycled fibers, taken from textile waste, in the field of composite materials to fulfill the eco-sustainability requirements of textile manufacturing, and promote actions for a circular economy. The yarns and fabric production represent one of the most polluting processes of the industrial world. The harmful environmental impact of the textile process has been described by reporting the different treatments involving the raw material and the filament fabrication, and concerning the uses of insecticides, fertilizers, and many other chemicals for improving the quality of the final products. In addition, solid textile waste constituted a further additional issue for the environmental sustainability of fabric production. Various strategies have been discussed and in part already adopted by many companies to recover waste fibers and prevent them from ending up in landfills. The alternatives of fiber recycling for composite realization have been presented by reporting several recent studies involving the uses of recycled fibers from the textile waste embedded in different matrices: thermoplastic polymer, thermosetting resins, natural constituents, and concrete in light of specific applications.

This study aims to provide an overview of the latest research studies on the use of biopolymers in various textile processes, from spinning processes to dyeing and finishing treatment, proposed as a possible solution to reduce the environmental impact of the textile industry. Recently, awareness of various polluting aspects of textile production, based on petroleum derivatives, has grown significantly. Environmental issues resulting from greenhouse gas emissions, and waste accumulation in nature and landfills, have pushed research activities toward more sustainable, low-impact alternatives. Polymers derived from renewable resources and/or with biodegradable characteristics were investigated as follows: (i) as constituent materials in yarn production, in view of their superior ability to be decomposed compared with common synthetic petroleum-derived plastics, positive antibacterial activities, good breathability, and mechanical properties; (ii) in textile finishing to act as biological catalysts; (iii) to impart specific functional properties to treated textiles; (iv) in 3D printing technologies on fabric surfaces to replace traditionally more pollutive dye-based and inkjet printing; and (v) in the implants for the treatment of dye-contaminated water. Finally, current projects led by well-known companies on the development of new materials for the textile market are presented.

Polyurethane is a polymer adaptable to different scientific and industrial requirements, nevertheless it is also extremely susceptible to UV radiation, which compromises the physical and mechanical functionality. In this framework, our study investigated the effect of waterborne polyurethane dispersion (WPUD) applied to a polyester (PET)-based fabric, through the impregnation method, on the puncturing and water resistance of the pristine material, before and after UV weathering. Results confirmed an increment of both features in the prepared fabrics, attributed to the PUR textile treatment, but a partially loss of the gained properties in the samples due to the UV weathering. In order to improve the efficiency of the impregnating dispersions, in protecting the durability of the treated materials, the addition of different UV light stabilizers, or/and of crosslinking agent into WPUD was also tested. From the experimental data, it can be concluded that formulations based on WPUD, containing both the crosslinker and UV organic absorber, have displayed an increment of their perforation and water resistance for the treated samples with respect to the starting textile, and contemporary have preserved the features against the UV light. Finally, microscopic and spectroscopic analyses have been performed as further characterization techniques of the samples surface.

Commercial waterborne polyurethane (PU) dispersions, different in chemistry and selected on the basis of eco-friendly components, have been applied to a common polypropylene (PP)-based woven fabric. Impregnation has been chosen as a textile treatment for improving the features of basic technical textiles in light of potential applicability in luggage and bag production. The effect of drying method, performed under conditions achieved by varying the process temperature and pressure, on the features of the treated textiles, has been verified. The prepared specimens were characterized in terms of mechanical behavior (tensile, tear and abrasion resistance) and water resistance (surface wettability and hydrostatic pressure throughout the treated textiles). The experimental results suggest an incremental improvement of the tensile features for all the investigated specimens. For tear strength, no augmentation compared to that of the neat textile, could be verified as a consequence of polyurethane treatment. Remarkable improvements of abrasion resistance were displayed for all the impregnated PP textiles. Benefits in water resistance could be attributed to the presence of hydrophobic PU in the textile weaving of the PP samples. The ultimate improvement in water resistance was dependent on drying conditions.

The reactivity of polylactic acid (PLA) with epoxidized natural rubber (ENR50) was confirmed by monitoring the changes in melt viscosity during mixing and by TGA runs. The plasticization resulting from a partial miscibilization of ENR50 during mixing was found to have opposite effects on the crystallization of the PLA matrix, depending on the temperature scanning mode. An increase in heat of crystallization (ΔHc) with increasing temperature scanning rate was observed when heated from the glassy state, while a corresponding reduction in ΔHc was obtained in cooling scans from the melt. Studies on the kinetics of events have shown that the classical Kissinger plots for crystallization by heating from the glassy state display a variable activation energy for the case of the reactive blend. The vitrification kinetics, on the other hand, could be modelled quite accurately with the Mahadevan method for all systems, including an intrinsically amorphous PLA.

Cellulose/PLA-based blends (up to 77 vol./vol.% of the added fibers) for applications in extrusion-based technology were realized in an internal mixer by setting different operating conditions. In particular, both the mixing time and temperature were increased in order to simulate a recycling operation (10 or 25 min, 170 or 190 &deg, C) and gain information on the potential reuse of the developed systems. The torque measurements during the compound&rsquo, s preparation, and the compound&rsquo, s mechanical tensile features, both in the static and dynamic mode, were evaluated for each investigated composition. The final results confirmed a reduction of the torque trend over time for the PLA matrix, which was attributed to a possible degradation mechanism, and confirmed by infrared spectroscopy. The mechanical behaviour of the pristine polymer changed from elastoplastic to brittle, with a significant loss in ductility going from the lower mixing temperatures up to the higher ones for the longest time. Through the addition of cellulose fibers into the composite systems, a higher stabilization of the torque in the time and an improvement in the mechanical performance were always verified compared to the neat PLA, with a maximum increase in the Young modulus (+100%) and the tensile strength (+57%), and a partial recovery of the ductility.

The wear resistance of several thermoplastic polyurethanes (TPUs) having different chemical nature and micron- scale arrangement of the hard and soft segments has been investigated by means of erosion and abrasion tests. The goal was correlating the erosion performances of the materials to their macroscopic mechanical properties. Unlike conventional tests, such as hardness and tensile measurements, viscoelastic analysis proved to be a valuable tool to study the erosion resistance of TPUs. In particular, a strict correlation was found between the erosion rate and the high-frequency (~10 7 Hz) loss mod- ulus. The latter reflects the actual ability of TPU to dissipate the impact energy of the erodent particles.

Films of semicrystalline poly(ε-caprolactone) (PCL) are fabricated by casting drops of fully biocompatible ethyl lactate (EL) and ethyl acetate (EA) solutions onto a glass substrate. The main goals of this work are: i) to assess the interplay among the physico-chemical properties of the solution and its interaction with the casting substrate; and ii) determine how the solution/substrate interactions influence the formation of the films and their final surface morphology and hydrophilicity. The competition between the rates of solution drop spreading and solvent evaporation controls the polymer crystallization process and the final film properties. Compared with EA, EL provides better wetting properties and a slower evaporation rate, eventually resulting in thinner films. The film thickness increases with polymer concentration in the solution; this parameter also affects the crystalline structure and, ultimately, the film surface roughness. As a result, the film hydrophilicity is finely tunable by changing the solution composition, so as to control the crystal nucleation density.

The low velocity impact behaviour of composites made of polypropylene (PP) as matrix and glass fibre fabric as reinforcement has been investigated. Two PP grades, differing for their melt flow index, have been used as matrix, and maleic anhydride has been used to manage the polymer/glass fibre interface strength. Impact tests at four energies (5, 20, 40 and 105 J) have been carried out to evaluate the main dissipation mechanisms occurring in each impact condition and to identify the role of the interface strength. Quasi-static flexural tests confirmed that the compatibilizer improves both flexural modulus and strength, as well as strain at yield. A different performance trend is shown by low velocity impact tests. Not compatibilized samples have exhibited, since the lowest impact energy (5 J), significant energy dissipation resulting from the interface failure occurring at very low strains, as confirmed by lock-in thermographic analysis. Conversely, compatibilized samples showed no or small damages. As the impact energy increases not compatibilized samples outperformed compatibilized samples by large margins showing better impact resistance. This result has been related to the large energy dissipation occurring at the polymer/fibre interface. Furthermore, the broad interface failure and slipping act as crack blocker, preserving the integrity of fibres and allowing for higher load bearing. Managing the interface strength can be a viable option to design thermoplastic based composites with improved impact damage tolerance and balanced quasi-static properties. © 2014 Elsevier Ltd. All rights reserved.

Composite laminates based on polyolefin wastes coming from two different sources are compared with similar systems involving a virgin polypropylene in terms of damage behavior. In particular, this paper reports the response of film-stacked composite laminate plates subjected to falling weight impact tests. As expected, samples based on recycled polyolefins show lower impact parameters with respect to the latter ones even if a partial improvement of the performances can be obtained by modification of the matrix by an adequate coupling agent. Despite the inferior impact behavior, potential uses of new systems provide an opportunity to develop valuable products by reducing the environmental impact of plastic wastes.

The influence of the main film production technologies, i.e. chill-roll extrusion and film blowing on the structural characteristics and mechanical performances of films based on a commercial thermoplastic polyurethane resin reinforced with carbon nanotubes has been studied. Structural investigations by means of X-ray diffraction and FTIR spectroscopic analysis have shown how the different processing conditions determine the mutual arrangement of soft and hard domains characteristic of the polyurethane matrix as well as the orientation and the final distribution of the included nanotubes as confirmed by electron microscopy observations. The higher the carbon nanotubes content, the higher the content and the size of segregated hard domains. Furthermore the film blowing process, characterized by relatively longer cooling times with respect to the extrusion process, allows a better self-assembly of hard domains maximizing the interdomain distance and, apparently, ensuring a worse distribution of the filler. By focusing on samples with 0.5 wt.% of carbon nanotubes, an increase of the tensile modulus with respect to neat TPU ones, approximately equal to 90% and 30% has been shown for flat and blown films, respectively. Morphological and structural considerations have provided a reasonable explanation of the mechanical behavior exhibited by the investigated films.

Carbon nanotubes effectiveness, as thermally conductor, in polymer/CNTs nanocomposites, is mainly related to various key aspects as dispersion, matrix/CNT interfacial resistance and inter-CNT contact resistance. Features of raw materials and processing parameters for the realization of nanotube/polymer composites, can simultaneously affect these critical issues, also in adverse way. In this contribution, polypropylene based-composites, containing multi walled carbon nanotubes (MWNTs), are prepared by melt-blending and then characterized prevalently in term of thermal transport behavior, choosing different matrix grades, filler functionalization and process conditions. In more details, two commercial polypropylene (PP) grades with different melt flow rates are considered as matrices and three kind of MWNTs with the same aspect ratio, one neat and two chemically modified with carboxyl –COOH and amino –NH2 groups, respectively, are used as fillers. The presence of a compatibilizer, as maleic anhydride grafted polypropylene (Ma-g-PP), and the use of various processing conditions as temperature, time, screw speed, pressure, filler drying and so on, are taken into account in order to optimize the thermal conductivity enhancement of PP/MWNTs compounds.

The potential of a multi-component laminate composite material in terms of improved flame retardancy and adequate mechanical performance is discussed. A double-layer system based on a biodegradable polyhydroxyalkanoates blend was obtained by compression molding. A thin halogen-free flame-retarded layer was located at the top of a kenaf-fiber-reinforced core. Kenaf fibers acted as a carbonization compound promoting charring and building up a superficial insulating layer that protected the material throughout combustion. The impact of different skin/core thickness on the thermal and fire properties was investigated. Synergistic flame retardancy occurs in the cone calorimeter. Chemical and fire investigations confirmed a changed pyrolysis behavior in multicomponent materials. Promising results are obtained in terms of mechanical performance: higher flexural and impact properties were observed in the single fiber-reinforced layer.

Three grades of polypropylene were tested in compression at room temperature, across an unusually wide range of strain rate: 10-4 to 104s-1. The quasi-static testing was done in a Hounsfield machine fitted with a digital image acquisition kit, while tests at the highest strain rates were carried out using a compression split Hopkinson pressure bar. The strain rate dependence of compressive yield stress was compared with the Eyring prediction, and found to be a nonlinear function of logio(strain-rate). The nonlinearity Is attributed to the presence of two relaxation processes in polypropylene, with differing activation volumes: the α- and β-processes. According to the Bauwens two-process model this would lead naturally to curved Eyring plots, where the apparent activation volume decreases with increasing strain-rate. Another prominent feature in the experimental results was the increase in magnitude of post-yield strain-softening with increase in strain-rate. This indicates that the dominant structural relaxation time exceeds the experimental time-scale at the highest strain-rates, but lies below It for the quasi-static tests. © 2008 American Institute of Physics.

The elasticity and structure of graphite nanoplatelets networks in polymer matrices are studied through linear viscoelastic analyses. GNPs-filled polystyrene nanocomposites at different filler content are prepared through a combination of solution and melt mixing techniques. Electrical volume conductivity experiments prove that a continuous path of conductive nanoplatelets builds up across the matrix above a critical filler content. GNP networks, however, are too tenuous to be detected through conventional dynamic-mechanical spectroscopy in the melt state. Nevertheless, we are able to estimate their elasticity by exploiting the predictive feature of a simple two-phase rheological model. Our approach, validated through the building of a master curve of the elastic modulus of samples at different composition, allows to isolate the elastic contribution of the bare GNP network, whose dynamics reveal that its elasticity follows critical behaviour as predicted by percolation theory.

The origins of the commercial exploitation of synthetic polymers and the subsequent industrial developments are reviewed, and the main landmarks are highlighted, starting from the pioneering work on the nitration of cellulose in the 19th century and progressing through various advancements to the latest innovations. This includes the contribution made by many authorities, starting from Staudinger, as the founder of polymer science, to the most recent Nobel laureates in the field. The increased awareness for the need to capture CO2 from combustion gases has stimulated interests in the possibility of using polymerization methods as a route to produce useful solid products. The available theoretical arguments and experimental evidence are presented in relation to the feasibility of producing linear polymers, both as homopolymer and copolymers, placing emphasis on stability aspects and possible uses of the products. The various claims on the possibility of opening both double bonds of molecular CO2 to produce stable networks are also analyzed. Arguments in support of the possibilities of producing mixed CO2–SiO2 glasses are provided, and the expected properties of the resulting solids are discussed. Suggestions are made for the possible utilization of such products. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 31: 179–192, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21275

We study the structure and linear viscoelasticity of interacting polymer nanocomposites based on mixtures of poly(ethylene oxide) and fumed silica particles. The filler is dispersed within the polymer using two different techniques which lead to different dispersion states. The analysis of the dynamic response of our systems highlights the formation of a stress-bearing network above a critical volume fraction, Φ(c). Extending a two-phase model used to describe weakly interacting systems, we show that above Φ(c) the melt-state elasticity of the composites arises from the independent contributions of a polymer-particle network and a viscous matrix. We also find that, although Φ(c) depends on the initial state of dispersion, the network elasticity scales with volume fraction following a universal power-law, with an exponent ν ≈ 1.8. Such a scaling law has been recently predicted for the stress-bearing mechanism governed by polymer-mediated interactions.

The addition of nanoparticles to polymer systems with an existing phase-separated morphology, such as polymer blends, represents an innovative approach to controlling the microstructure and, hence, the macroscopic properties of the material. During the melt mixing of the constituents, the particles migrate toward specific regions of the material and are driven by more favorable thermodynamic interactions. Kinetic effects related to the high viscosity of the polymer melts, however, may lead to nonequilibrium morphologies. This makes the mixing procedure crucial for controlling the space distribution of the filler and, hence, the microstructure of the blend and its final properties. We focused on this topic by investigating the effect of the sequence of addition of the constituents in blends of polystyrene and polyamide 6 filled with an organoclay prepared by melt compounding. We show that the mixing procedure could bring about alterations in the onset of cocontinuity, which could be exploited to enhance the high-temperature mechanical strength of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The known flame-retardant synergism between phosphorus-based additives and metal oxides, already used for petroleum-based plastics, has been extended to bio-based materials. The pyrolysis and the flame-retardancy properties of aluminium phosphinate (AlPi) in combination with nanometric iron oxide and antimony oxide on a poly(3-hydroxy-butyrate-co-3-hydroxyvalerate)/poly(butylene adipate-co-terephthalate) (PHBV/PBAT) blend were investigated. Better fire retardancy, ascribed to increases in intermediate char, favoured improvements in the UL 94 classification. Both the phosphorus and the nanofiller components participate simultaneously in the flame-retardancy mechanism: the first acting as flame inhibition in the gas phase, and the second promoting cross-linking in the solid phase. Redox reactions between iron oxide and the phosphinate additive were confirmed by XRD analysis and provided further evidence of the activity of metal compounds.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This paper has been retracted at the request of the authors. A more detailed description of the research has been published in Surface & Coatings Technology (SCT 243, pages 65–70 (http://dx.doi.org/10.1016/j.surfcoat.2012.03.030).

The impact of small amounts of organomodified clay (OMMT) on the photo-degradation behaviour of two blends obtained by mixing either low-density polyethylene (LDPE) or high density polyethylene (HDPE) with polyamide 6 (PA6) (LDPE/PA6 and HDPE/PA6 75/25 wt-%) was studied. The complex photo-degradation behaviour was followed by monitoring the main physical–mechanical properties of the blends. In particular, mechanical and spectroscopic tests were performed in conditions of accelerated artificial aging. An accurate mechanical and morphological characterization was previously carried out. The presence of the OMMT promotes the unexpected formation of a co-continuous morphology for the HDPE/PA6 blend without significantly improving the interfacial adhesion. Differently, the OMMT-filled LDPE/PA6 blend exhibits a finely distributed morphology, and some apparent improvement of the interfacial adhesion was noticed. Probably due to these differences in microstructure, a different impact of the nanoparticles on the photo-resistance behaviours was observed for the two families of samples. In particular, the HDPE-based nanocomposite blend exhibits an improved photo-resistance, while the opposite occurs for the LDPE-based system.

We investigate the relation between structure and viscoelasticity of model polymer nanocomposite systems based on a mixture of spherical nanoparticles and different polymer matrices. When Brownian motions become relevant, the composites exhibit a strong time dependence of the linear visoelastic moduli, which is indicative of the three-dimensional structuring of the filler in the melt polymer. Despite the complexity of the rheological response, we show that the viscoelasticity of the samples can be rationalized by splitting it into the independent responses of the “viscous” suspending polymer melt and that of the “elastic” particle network. Besides underlying the similarities between polymer-based nanocomposites and Newtonian colloidal suspensions, our analysis is expected to be useful for understanding the behavior of other complex fluids where the elasticity of the components may be superimposed.

The effect of organically modified clay on the morphology, rheology and mechanical properties of high-density polyethylene (HDPE) and polyamide 6 (PA6) blends (HDPE/PA6 ¼ 75/25 parts) is studied. Virgin and filled blends were prepared by melt compounding the constituents using a twin-screw extruder. The influence of the organoclay on the morphology of the hybrid was deeply investigated by means of wide-angle X-ray diffractometry, transmission and scanning electron microscopies and quantitative extraction experiments. It has been found that the organoclay exclusively places inside the more hydrophilic polyamide phase during the melt compounding. The extrusion process promotes the formation of highly elongated and separated organoclay-rich PA6 domains. Despite its low volume fraction, the filled minor phase eventually merges once the extruded pellets are melted again, giving rise to a co-continuous microstructure. Remarkably, such a morphology persists for long time in the melt state. A possible compatibilizing action related to the organoclay has been investigated by comparing the morphology of the hybrid blend with that of a blend compatibilized using an ethyleneeacrylic acid (EAA) copolymer as a compatibilizer precursor. The former remains phase separated, indicating that the filler does not promote the enhancement of the interfacial adhesion. The macroscopic properties of the hybrid blend were interpreted in the light of its morphology. The melt state dynamics of the materials were probed by means of linear viscoelastic measurements. Many peculiar rheological features of polymer-layered silicate nanocomposites based on single polymer matrix were detected for the hybrid blend. The results have been interpreted proposing the existence of two distinct populations of dynamical species: HDPE not interacting with the filler, and a slower species, constituted by the organoclay-rich polyamide phase, which slackened dynamics stabilize the morphology in the melt state. In the solid state, both the reinforcement effect of the filler and the co-continuous microstructure promote the enhancement of the tensile modulus. Our results demonstrate that adding nanoparticles to polymer blends allows tailoring the final properties of the hybrid, potentially leading to high-performance materials which combine the advantages of polymer blends and the merits of polymer nanocomposites.

Three types of multiwall carbon nanotubes, one non-functionalized tubes and two functionalized with polar (amino and carboxyl) groups, were used as fillers in a polypropylene resin to develop nanocomposites with improved thermal conductivity. In particular, formulations containing up to 5% in volume of carbon nanotubes, prepared by melt blending, were analyzed in terms of dynamic rheological behavior of melts and thermal conductivity. The former can give information related to the build-up of internal network structures and to the level of dispersion of the fillers. Taking into account that the properties of nanocomposites are strictly related to these aspects, the enhancement of thermal conductivity with respect to the pristine matrix are discussed as a function of the filler content, dispersion of the filler and presence of internal structures.

Polypropylene (PP) resins, widely used in several industrial applications, are still the object of research interests with the aim to improve specific functional properties. As a well-known weakness of plastics is their low thermal conductivity, a great deal of attention is paid to explore the possibility to enhance thermal conductivity of polymers through the addition of conductive particles. Although particle composites suffer the limitation that high filler loadings can give rise to high viscosities and poor processability, recent studies have shown that hybrid systems developed by using different (in shape and nature) particles can give rise to specific conductive paths with limited particle concentrations. In this view - and with the aim of improving thermal conductivity of a commercial polypropylene without sacrificing its extrudability - we have prepared binary, containing up to 2.5% in vol. of multiwalled carbon nanotubes (MWNT), and ternary nanocomposites, containing 1.5% in vol. of the same carbon nanotubes and 10% in vol. of an additional filler (boron nitride, calcium carbonate, zinc oxide, talc, respectively). The hybrid ternary systems (PP/MWNT/secondary filler) show a remarkable enhancement of thermal conductivities with respect to binary ones (PP/MWNT) while rheological tests demonstrated that their extrudability remain acceptable.

Biocomposite laminates based on poly(lactic acid) (PLA) and woven jute fabric were obtained by film stacking and compression molding techniques. Sample laminates were systematically characterized by impact tests with a falling dart at impact energies equal to 5, 10 and 20 J. Tests showed that, investigated PLA/jute fabric plates suffer only barely visible damages at the first two levels of impact energy while they result to be perforated at 20 J as highlighted by photographic images taken on low and back side of impacted surfaces.

The influence of plate-like nanoparticles on the morphology evolution of co-continuous polymer blends during quiescent annealing is investigated thorugh viscoelastic analysis. Contextually, the effect of the molten polymer phases on the assembly dynamics and ultimate structure of the filler is also studied. A model co-continuous blend of polystyrene and poly(methyl methacrylate) (45/55 wt/wt) has been selected, and different amount of clay nanoparticles preferentially adsorbing at the polymer-polymer interface are added to this system. The filler inhibits the typical phase coarsening of the co-continuous morphology during thermal treatments even at extremely low filler volume fractions (Φ=0.4 vol.%). In addition, the time evolution of the rheological response of the filled blends resembles that of homopolymer-based nanocomposites, suggesting that the fluid phases do not appreciably alter the nanoparticle dynamics. Exploiting a simple two-phase model, the main elastic features of the filler network that builds up at sufficiently high Φ were found to prescind from the multiphasic nature of the matrix. Nonetheless, the presence of a co-continuous polymer microstructure prevented the elastic and structural features of the network to be discerned through the use of fractal models.

This paper deals with melt blended polypropylene based nanocomposites filled with multi wall carbon nanotubes. The effect of the content of unfunctionalized, amino- and carboxyl-functionalized carbon nanotubes having the same aspect ratio on their actual dispersion is investigated by dynamic rheological measurements and transmission electron microscopy observations. In particular, the former tests highlight a greater propensity to percolate of non functionalized nanotubes with respect to amino surface modified ones and even the absence of terminal effects in presence of carboxyl functionalized carbon nanotubes. Morphological observations, instead, show dispersion and agglomeration effects typically expected by increasing the carbon nanotubes loading. Moreover, through-plane steady-state evaluations of their thermal conductivity reveal a cubic polynomial trend of this parameter as a function of the filler content. This behaviour is interpreted in terms of the “average inter-aggregate distance (AID)” related to competitive dispersion/agglomeration phenomena to which added multi wall carbon nanotubes are subjected during the preparation of compounds with concentrations over specific threshold values.

Summary: Reuse and recycling of tires at the end of their useful life is an environmental challenge owing to the huge volumes discarded all over the world. This paper tries to give a scientific contribution toward the mechanical recycling of elastomers derived from pre treatment of tires to produce anti-shock tiles and heat-insulating panels for civil applications. Thermal and mechanical results herein reported satisfactorily justify the interest devoted by now to this topic.

The possibility of improving the processing characteristics of a high-viscosity engineering polymer alloy (PPO-PA6,6) was explored through the addition of small amounts of a thermotropic liquid crystalline polymer (LCP). The thermal and rheological characteristics were examined for LCP contents up to 5 wt%. Inclusion of even a small amount of LCP (1 wt%) has resulted in a substantial decrease in the melt viscosity (∼50%) and in the possible lowering of the processing temperature of the PPO–PA alloy. Numerical simulation and experimental tests for the injection molding of a fairly complex component have shown that cavity filling occurs more rapidly when small amounts of LCP are added to the blend. Together with morphological examinations, these results have confirmed that LCP is thoroughly dispersed in the blend and acts as a true viscosity depressant, rather than behaving as an external lubricant. The resulting improvements in processing characteristics were also evident from the increase in the onset degradation temperature and the reduction in thermal expansion coefficient of the blends. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:109–120, 2007; Published online in Wiley InterScience www.interscience.wiley.com). DOI 10.1002/adv.20089