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Air pollution is one of the major global problems causing around 7 million dead per year. In fact, a connection between infectious disease transmission, including COVID-19, and air pollution has been proved: COVID-19 consequences on human health are found to be more severe in areas characterized by high levels of particulate matter (PM). Therefore, after the COVID-19 pandemic, the production of air filtration devices with high filtration efficiency has gained more and more attention. Herein, a review of the post-COVID-19 pandemic progress in nanofibrous polymeric membranes for air filtration is provided. First, a brief discussion on the different types of filtration mechanism and the key parameters of air filtration is proposed. The materials recently used for the production of nanofibrous filter membranes are presented, distinguishing between non-biodegradable polymeric materials and biodegradable ones. Subsequently, production technique proposed for the fabrication of nanofibrous membranes, i.e., electrospinning and solution blow spinning, are presented aiming to analyze and compare filtration efficiency, pressure drop, reusability and durability of the different polymeric system processed with different techniques. Finally, present challenges and future perspectives of nanofibrous polymeric membranes for air filtration are discussed with a particular emphasis on strategies to produce greener and more performant devices.

The use of biodegradable polymers for the production of membranes to be used in wastewater treatment has attracted increasing interest considering the possibility of reducing the risk of second pollution. In this work, porous fibrous membranes based on polylactic acid and polyethylene oxide (PEO) blends were prepared. The solutions were electrospun using two approaches: (i) conventional coaxial electrospinning followed by leaching treatment (double-step, DS); (ii) coaxial wet electrospinning with in situ leaching (single-step, SS). By varying PEO type and processing method it was possible to control membranes structure and porosity. DS leaching treatment lead to surface porosity (i.e. shell leaching), while SS allowed obtaining hollow and porous fibers (i.e. with shell and core leaching). Process, properties and structure relationships of devices were analysed trough rheological, morphological, mechanical and surface characterizations. Furthermore, the influence of the different porous structures on oil sorption capacity and reusability of the membranes was evaluated. Results reveal that different porosities lead to a variation in membranes mechanical performance, in their wettability and, consequently, in their oil spill cleanup capacity. Membranes obtained with SS displayed higher performance in oil removal if compared to the DS ones, due to their hollow structure and higher surface area.

Platelet-like and fibrous lignocellulosic fillers were achieved from the leaves of Chamaerops humilis (CHL) and Posidonia oceanica (POL) and used as a hybrid reinforcement for a polylactic acid (PLA) matrix at three different loading levels (from 5 to 20%). The materials were fully characterized from a morphological, physicochemical, mechanical, and dynamic-thermomechanical point of view. When compared to their counterpart containing either CHL or POL only, the resulting hybrid biocomposites showed the highest mechanical properties, with strengthening and stiffening effects respectively up to 120% and 50% higher than those expected from the linear combination of the two, and higher dynamic-mechanical performance, with storage moduli in the rubbery region 10 times higher than those of composites containing solely CHL or POL. Such synergistic efficiency is likely due to the formation of a strong and extensive interphase region, promoted by the balanced effect of morphological features of the hybrid network and physicochemical characteristics of the components. These green materials could find applications as panels for furniture or in the automotive industry. Graphical Abstract

Ionic tactile sensors (ITS) are an emerging subfield of wearable electronics, capable of mimicking the human skin, including not only the typical anisotropic structure, mechanical behaviour, and tactile functions but even the mechanosensitive ionic channels that are crucial for the human sense of touch. With the rapid development of intelligent technology, such bioinspired materials constitute the core foundation of intelligent systems and are a candidate to be the next generation e-skins, offering a more accurate and evolved biointerface. In the latest years, a wealth of novel ultra-stretchable ITS was proposed, progressively refining the choice of soft materials, including ion gels, ionic liquids and hydrogels, and fabrication techniques. Regardless of materials and methods adopted, all these tactile sensors can feel mechanical solicitations and external stimuli, thus behaving as – or even better than – human skin. In this review, an overview of the very latest advances in high-performance ITS applied in intelligent systems is reported. First, generality of ITS will be summarized. After, ion gel, ionic liquid, hydrogel, and elastomer ITS will be discussed focusing first on composition, fabrication, type and mode of sensing and then on their characteristics and application. In this perspective, the advantages that biomimetic approaches brought in terms of sensitivity, speed of response and multimodality of sensing will be highlighted, with a particular focus on the development of electrochromic, thermochromic, self-powered and self-healing devices. In conclusion, the prospects of tactile sensors for intelligent systems in biomedicine and robotics will be discussed, along with the possible strategies to overcome the current shortcomings, in terms of biocompatibility, durability, mechanical performance, adhesion to biological substrates, which represent the future challenges.

The usefulness of any material, including polymer blends, depends on its degradability and durability. The blend composition can significantly affect the degradative behavior of a polymer blend and can differ from the degradation routes of the pure components since the interactions among different species in the blends during degradation, and among the degradation products, can occur. These reactions can lead either to an acceleration of the degradation rate or to a stabilizing effect in comparison with the pure components. Thus, the additive rule cannot be often applied in case of degradation of polymer blends and, therefore, it is difficult to predict the degradative behavior of a polymer blend on the base of the properties of pure components. This review aims to report the status of the research on degradation of polymer blends focusing on thermal, thermomechanical and photo-oxidative degradation.

A novel floatable and biodegradable sponge for the selective absorption of oil from water and potentially useful as cell carrier for bioremediation treatments was prepared in polycaprolactone (PCL). The eco-friendly process for fabricating the PCL sponge does not involve either synthetic routes or organic solvents, thus minimizing environmental hazard. In particular, the 3D porous materials have been prepared by mixing in the melt the polymer matrix with two water-soluble porogen agents (NaCl and PEG) and thereafter leaching the obtained PCL/NaCl/PEG composites in water. The PCL sponges here proposed are capable to remove different types of oily pollutants (up to 500 wt%), and were successfully tested as carrier materials of hydrocarbon(HC)-degrading bacteria for bioremediation. The bioremediation efficiency of the scaffold-bacteria system was analyzed on crude oil and n -alkanes using two highly performant HC-degrading bacterial strains: the marine hydrocarbonoclastic model strain Alcanivorax borkumensis SK2 and the soil long-chain n -alkane degrader Nocardia sp. SoB. Morphological analysis highlighted a high capacity of adhesion and proliferation of bacterial cells within the whole interconnected three-dimensional structure. HC degradation rates, evaluated by GC-FID analysis, demonstrated the higher degrading performance of immobilized-cells if compared with conventional submerged liquid culture.

In this work, we report the effect of an organoclay on the photochemical weathering of nanocomposites based on a poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) (PLA) blend. The evolution of physicochemical properties was monitored by integrating spectroscopic, mechanical, and morphological analyses. A robust relationship was found between the molecular transformations of the polymer macromolecules and the morpho-mechanical properties of irradiated films. Moreover, the analysis of insoluble fractions extracted from nanocomposites pointed out that free-standing, porous structures, displaying an unprecedented thickness as great as 100 µm, were formed, thus unambiguously demonstrating that the organoclay increased the propagation depth of photochemical crosslinking reactions by 10 times with respect to previously reported results on PBAT. The pore architecture and chemical structure of such crosslinked networks proved to change depending on organoclay content of films.

International audience; In the present study, the possibility to synthesize graphene oxide (GO)-based nanohybrids with pure and O2-doped silica nanoparticles by a rapid and easy hydrothermal process has been explored. The nanohybrids were prepared by varying the type of silica nanoparticles (average diameter 7 nm or 40 nm) and the silica/GO weight ratio. All the materials were fully characterized by spectroscopic and morphological techniques.The experimental results revealed that it is possible to tune the characteristics of the obtained nanohybrids, such as morphology and amount of ester/ether linkages upon varying the preparation parameters, together with the nanosilica's typology and the silica to GO ratio. By Fischer esterification it was possible to achieve GO-silica nanohybrid lamellae to be then reduced into nanostructured films by a hydrothermal process. These latter materials show a “lasagna-like” structure in which it is possible to observe fully exfoliated (and partially reduced) GO lamellae intercalated by silica nanoparticles agglomerates. The extension of silica layers, film morphology and structure, degree of functionalization, and thermal stability are strongly affected by the type of silica. Furthermore, after the hydrothermal treatment, the nanohybrids were found to be insoluble in water.

A novel approach was designed to fabricate high-added value manufacts, starting from cost-effective materials and combining well-known processing techniques. Bi- and three-layered, functionally graded laminates were achieved by direct electrospinning onto dense substrates. The architecture of each multilayer comprises a dense layer formed by solvent casting, which is constituted by polylactic acid (PLA) and carvacrol, and one or two electrospun fibrous skin layers, consisting of PLA only. Processing-structure-properties relationships of such materials were investigated. As regards mechanical behavior, the amount of fibrous PLA layers determined an increase of stiffness from 20 to 35 MPa, adequately predicted by isostrain model, whereas the breaking properties proved to be governed by the dense layer, with values of tensile strength (6 MPa) and elongation at break (200%) almost ten-folded with respect to those of electrospun fibrous PLA. As concerns carvacrol release behavior, the presence of fibrous skin, especially in three-layered structures, proved to progressively reduce the burst delivery at early stage of immersion, while enhancing the depletion time, i.e. the release activity, of such devices from 288 to 795 h. Furthermore, a correlation was found between the thickness of fibrous layers and release kinetics, thus suggesting that adjusting simple variables, such as electrospinning time, allows to control the ultimate properties of these devices. Moreover, this approach enables gathering the mechanical robustness of a dense film with the extremely large specific area of fibrous materials, thus showing promising potential for a broad range of application fields.

In this work, the feasibility of antibacterial biopolymeric foams containing carvacrol (CRV) for potential food packaging applications was investigated. Sodium bicarbonate (SB) was chosen as foaming agent and a commercial biodegradable polymer, Mater-Bi® (MB), as a matrix. MB/SB and MB/SB/CRV systems were prepared by melt mixing and the foaming process was conducted in a laboratory press. The influence of foaming agent and antibacterial additive content was investigated. The foamed samples were characterized through morphological analysis, mechanical tests and measurements of CRV release kinetics. Moreover, a mathematical model, i.e. power law model, was used to fit the release data in order to investigate the release mechanism. The antibacterial activity of foams containing CRV was tested in vitro against pro-technological, spoilage and pathogenic bacteria applying the disc diffusion method. The results showed that by using 3% of SB it is possible obtain foams with a porosity of about 40%. The presence of carvacrol, strongly influenced the properties of the biopolymeric foams but at the higher content ensured antibacterial activity of the samples.

In this work, polylactic acid (PLA) membranes at two different carvacrol (CRV) nominal concentration (i.e. 14 wt% and 28 wt%) were prepared via electrospinning technology. The membranes were characterized by scanning electron microscopy, ATR-FTIR and calorimetric measurements as well as tensile tests. Moreover, the release kinetics of CRV in phosphate buffered solution at 37 °C was monitored through UV–Vis measurements and the data were fitted with a power law model. Results indicated that the successful incorporation of CRV in the polymer matrix damaged the fibers morphology but increased all the mechanical parameters investigated (i.e. elastic modulus, tensile strength and elongation). The power law model highlighted that the mechanism of CRV release changed with time from an anomalous release in the first 6 h to a Fickian diffusion mechanism for both the PLA/CRV systems.

In order to develop scaffold able to mimic the natural gradient properties of tissues, biphasic and triphasic approaches were adopted. In this work, polycaprolactone/polyethylene glycol (PCL/PEG) scaffolds were prepared by using a combination of melt mixing and selective leaching without harmful solvents. The method permitted to develop three-layer scaffolds with high control of porosity and pore size. The mechanical properties were evaluated under physiological condition in order to simulate the real conditions of work. Co-culture of osteoblastic and fibroblastic mice cells were carried out in order to study the differential cellular permeation through the different pore size layers.

In this work, we prepared poly(caprolactone) (PCL) monofilaments incorporating different amounts of the antiseptic chlorhexidine diacetate (CHX) and evaluated the effect of “online” drawing during the melt spinning or of an “offline” cold drawing on the antimicrobial and physical properties of PCL/CHX monofilaments. The results showed that the drawing conditions strongly affected the properties of the threads. In particular, the filaments exhibited antimicrobial activity for all the draw ratios (DR) adopted, but on increasing DR the antibacterial efficiency reduced. These results were correlated with the CHX surface concentration and with the release kinetics.

PLA/PCL co-mingled nanofibrous mats were prepared via multi-jet electrospinning. The concentration of PLA and PCL in the co-mingled mats were controlled by changing the flow rate of the two polymer solutions. The amount of PLA and PCL in the co-mingled nanofibrous mats was monitored by UV–Vis measurements through a colored dye added to PLA and by FTIR-ATR analysis. Morphology and mechanical properties of the nanofibrous mats were respectively examined by scanning electron microscopy (SEM) and tensile tests. Water contact angles measurements were also carried out in order to investigate the wettability of the materials. Finally, the hydrolytic degradation of the mats in buffer solution at pH 4, pH 7 and pH 10 were studied up to 50 days.

In this work the effect of multiple reprocessing was studied on molecular structure, morphology and properties of poly(lactic acid)/hydrotalcites (PLA/HT) nanocomposites compared to neat PLA. In addition, the influence of two different kinds of HT – organically modified (OM-HT) and unmodified (U-HT) – was evaluated. Thermo-mechanical degradation was induced by means of five subsequent extrusion cycles. The performance of the recycled materials was investigated by mechanical and rheological tests, differential scanning calorimetry (DSC), intrinsic viscosity measurements and SEM observation. The results indicated that the best morphology was achieved in the systems incorporating OM-HT. On increasing the extrusion reprocessing cycles, the properties showed behavior due to two opposite effects: i) chain scission due to thermo-mechanical degradation and ii) filler dispersion effect resulting from multiple processing. In particular, at low reprocessing cycles, both tensile and rheological properties seem to be mainly affected by HT dispersion, especially when OM-HT was added. After five reprocessing cycles, on the contrary, chain scission, i.e. thermo-mechanical degradation, dominated. As regards the effect of the presence of organic modifier in HT, the results indicated that this variable apparently did not affect the macroscopic performance of the nanocomposites, especially at high reprocessing cycles.

The investigation of the thermal stability up to 400 °C of Graphene Oxide (GO) and GO-silica nanoparticles (n-SiO2) composites prepared by direct mixture of GO and n-SiO2 is reported. Using Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, Energy Dispersive X-ray analysis, Atomic Force Microscopy, Raman and Infrared absorption measurements a thorough characterization of the prepared materials is carried out. By deepening the changes induced in the 2D Raman spectral region of GO at about 2900 cm−1 the comprehension of an interplay, driven by the thermally induced changes of the material, between inter-valley and intra-valley vibrational transitions is elucidated. This result enables to find out that the major thermally induced changes are related to the GO counterpart of the nanocomposite and shows that the deposited silica nanoparticles are not interfering with the GO principal features exploiting the potentiality of nanocomposites preparation. Furthermore, silica nanoparticles are found to act as solid exfoliant agents, thus inhibiting GO lamellae re-aggregation even at high temperatures.

Composites obtained from biodegradable polymers and natural–organic fillers are attracting increasing interest, thanks to the environmental advantages they promise. On the other hand, the real biodegradation performance of a biodegradable polymer/natural organic filler composite should be assessed by performing specific biodegradation tests. These are often carried out under laboratory conditions, but more realistic conditions should be taken into account. In this work, a systematic study on the biodegradation of kenaf fiber-filled Mater-Bi® composites in different environments is presented, and some interesting parameters for the understanding of the optimum way to obtain a fast degradation of the composites can be extrapolated. In particular, it was found that the presence of the fibers, the environmental conditions, and the manufacturing procedures of the composites can significantly affect the biodegradation behavior. The results can be used to determine the most suitable disposal environments for biodegradation of Mater-Bi®-based wastes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The actinomycetes, Gram-positive filamentous bacteria, are the most prolific source of natural occurring antibiotics. At an industrial level, antibiotics from actinomycete strains are produced by means of submerged fermentations, where one of the major factors negatively affecting bioproductivity is the pellet-shaped biomass growth. The immobilization of microorganisms on properly chosen supports prevents cell-cell aggregation resulting in improving the biosynthetic capability. Thus, novel porous biopolymer-based devices are developed by combining melt mixing and particulate leaching. In particular, polycaprolactone (PCL), polyethylene glycol (PEG), and sodium chloride (NaCl) with different grain sizes are used to prepare PCL/PEG/NaCl blends in the melt. These blends are then leached to obtain PCL-based porous membranes that are used as solid support for the growth of Streptomyces coelicolor, a model streptomycete used to produce various antibiotics including the blue colored actinorhodin (ACT). Thereafter, the effect of the devices' characteristics on the bacterial growth and on the production ACT is evaluated. The results showed that ACT production is strongly dependent on the pore size distribution of the device. Moreover, membranes with pores ranging from 90 to 110 μm are able to offer a potential improvement in volumetric productivity of ACT if compared to conventional submerged liquid culture.

Virgin/post-consumer ABS (pc-ABS) blends were re-processed and re-formed up to three times. The effect of pc-ABS content and of reprocessing cycles on the physical properties of the prepared blends was evaluated by mechanical tests (tensile, flexural and impact tests) and by rheological and thermo-mechanical measurements. The processability of pc-ABS blends was not substantially different by that of virgin ABS up to two recycling steps even if the third one induced a slightly decrease of viscosity, more remarkable on increasing the pc-ABS content. The mechanical and thermo-mechanical properties of the samples worsened on increasing the level of pc-ABS and after each reprocessing operation even if the most relevant decreases were observed after the first recycling.

Surface modification of polymeric films is a way to obtain final products with high performance for many specific and ad hoc tailored applications, e.g. in functional packaging, tissue engineering or (bio)sensing. The present work reports, for the first time, on the design and development of surface modified ethylene–acrylic acid copolymer (EAA) films with polyaniline (PANI), with the aim of inducing electrical conductivity and potentially enable the electronic control of a range of physical and chemical properties of the film surface, via a new “grafting from” approach. In particular, we demonstrate that PANI was successfully polymerized and covalently grafted onto flexible EAA substrates, previously activated. The final hybrid materials and the corresponding intermediates were fully characterized via FTIR, XPS, SEM–EDAX, mechanical and electrical tests. The mechanical properties of the films are not detrimentally affected by each treatment step, while a significant increase in electrical conductivity was achieved for the new hybrid materials.

In this paper, the processability and the performance of a biodegradable polymer, Mater-Bi, and of its blends with either a sample of poly (hydroxy alkanoates) (PHA) or with bacterial biomass containing PHAs were compared. Adding PHA or directly the biomass containing it allows improving the processability of the matrix. Moreover, the mechanical behaviour of the systems was compared considering two different preparation methods, namely compression and injection moulding. The injection moulded samples show poorer mechanical performances than those of the compression moulded systems. The impact strength significantly improves when PHA is added while it reduces when bacterial biomass is used instead. In this latter case this was likely due to the easier propagation of micro-cracks during the impact tests.

In this work we report the properties of nanocomposite based on PET with two different samples of organically modified montmorillonites. In particular, we studied the effect of the filler concentration on morphology, rheology, and mechanical performance, focusing our attention on the effect of the degradation phenomena of the clay modifiers. The results indicate that at low clay level the morphology achieved is mainly intercalated. On increasing the filler level, coalescence and/or bad defragmentation phenomena induce a coarser morphology, as confirmed by XRD, SEM, and TEM observations. When a more polar organic modifier is used to modify the clay, the particle adhesion and distribution is slightly better. Conversely, at the processing temperatures adopted, this organic modifier induces a strong degradation of PET, as confirmed by melt rheology and intrinsic viscosity measurements. DSC indicates, in addition, a slight increase of crystallinity likely due to the decreased molecular weight. As regards the mechanical properties, Young's modulus is not significantly changed unless high amounts of clay (10%) are used while the elongation at break drops even at the lowest clay content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Several compatibilising systems were added to high-density polyethylene (HDPE) and polyamide 6 (PA6) blends in the presence of an organically modified montmorillonite (OMM). All the blends were prepared by using a co-rotating twin-screw extruder and characterized by SEM, TEM and XRD analyses. In addition, the rheological behaviour and the mechanical properties – tensile and impact – were evaluated. The presence of OMM affects the dimensions of the polymeric phases in the blend but not their mutual adhesion, granted only by the compatibilisers. TEM, SEM and XRD analyses indicated that there is a strict correlation between the compatibilisation level and the final interlayer distance achieved by OMM. Even if some filled compatibilised blends showed a fairly good morphology – in terms of phase adhesion, dispersion and dimension – the mechanical performance was not so satisfactory. These results were interpreted considering the possible thermo-oxidative degradation of the organic modifier of OMM and the subsequent interaction between and the degradation products and the compatibilising systems. In order to prevent these phenomena, a stabilizing system was added to the nanocomposite blends. In this case, an improvement of mechanical properties was achieved.

Poly(lacticacid)(PLA)hasbeengainingarisinginterestoverthe last years as a biodegradable and environmental-friendly substitute of traditional non-biodegradable poly-mers.Several ways exist to synthesize PLA, however, poly-merization through lactide formation is the most used onindustrial scale, allowing to obtain optimum results interms of mechanical and thermal properties.

In this work, a comprehensive study of the rheological behavior under shear and isothermal and nonisothermal elongational flow of low density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA) based nanocomposites was reported to evaluate their "filmability", that is, the ability of these material to be processed for film forming applications. The influence of two different kinds of organoclay - namely Cloisite 15A and Cloisite 30B - and their concentration was evaluated. The presence of filler clearly affects the rheological behavior in oscillatory state of polyolefin-based nanocomposites but the increase of complex viscosity and the shear thinning are not dramatic. A larger strain-hardening effect in isothermal elongational flow is shown by the nanocomposites compared to that of the pure matrix, particularly for EVA based nanocomposites. The melt strength measured under nonisothermal elongational flow increases in the presence of the nanofiller, while the drawability is only slightly lower than that measured for the neat matrix. Moreover, the rheological behavior under nonisothermal elongational flow of EVA-based nanocomposites is similar for both nanoclays used. Differently, LDPE-based nanocomposites show a strong dependence on the type of organoclay. Finally, the mechanical properties of the materials were measured by tensile tests. They revealed that the presence of the filler provokes, in all the cases, an increase of the rigidity.

Polymer composites based on biodegradable polymers and natural-organic fillers are becoming more and more important because of their interesting properties in terms of environmental impact, manufacturing cost, and esthetic features. In particular, the use of biodegradable polymer matrices allows obtaining a full biodegradability. One of the most interesting biodegradable polymer families is the Mater-Bi® one. In this work, we investigated the processability, the influence of different processing techniques, and the influence of the filler particle size on the properties of Mater-Bi/wood flour composites. Injection molding caused a partial degradation of the macromolecular chains, whereas single-screw extrusion followed by calendering and twin-screw extrusion provoked an increase of the elastic modulus and of the viscosity. The use of wood flour led to a significant increase of the rigidity, whereas a reduction of the ductility was observed. Because of the very similar aspect ratios of the two different filler size classes, no dramatic differences in the properties were found. These results are useful in order predicting and setting up the optimum preparation and processing strategy for the production of fully biodegradable polymer composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Specific reactions of amino and carboxyl end groups of Nylon 6 with the reactive oxazoline groups belonging to a cyclophosphazene compound (referred as CP20XA) were carried out at 240 °C for different times, under inert atmosphere. Ny6 polymers terminated with one specific reactive chain end (-COOH or NH2) were reacted with different amounts of CP20XA to study the kinetic order of the reactions. All Ny6-CP20XA reacted products soluble in trifluoroethanol (TFE) were well characterized by MALDI-TOF MS, FT-IR and ( 1H and 13C) NMR techniques. The MALDI-TOF results show that the oxazoline rings react with the carboxyl chain ends of Ny6 following second-order kinetics. The reactions with amino chain ends are very fast and high amounts of gels are produced in just 5 min heating, whereas traces of gel are formed when Ny6C00H and CP-20XA are reacted for 60 min. The gels were characterized by FTIR analyses, and also by MALDI-TOF MS after partial acid hydrolysis. MALDI-TOF mass spectra reveal also that oxazoline rings can react with -NH amide groups along the Ny6 chains, and with secondary amino groups formed by a condensation reaction involving the elimination of ammonia from two amino chain ends. These side reactions could be responsible of the formation of the gels. The polymerization of CP20XA was also observed, and the oligomers formed could also react with Ny6 samples during the melt mixing.

These kinds of filmshave,asaprimaryaim,tocreateafavorablemicro-climateto accelerate the plant growth.Thematerialsfortheseapplicationsmustpossessseveralspecificandpeculiarcharacteristics,suchastheabilitytobeshaped into films (even with wide dimensions and largethickness ranges), good deformability and tear resistancetogetherwithasufficientrigidity,transparencyforUVandIR radiation in particular regions of the spectrum, a goodresistance to photo-oxidative phenomena and for someapplications to provide a barrier for certain gases.Moreover, an important property requested for thematerials used for greenhouse covering is the capabilityto diffuse the light. In fact, according to some studies,diffused light makes easier the plant growth and preventsdamages caused by an excessive warming of the environ-ment.

The influence of an elongational flow on the morphology of PE/clay nanocomposite drawn fibers was studied. An increase of the elastic modulus and the tensile strength as well as a decrease of the elongation at break are observed with increasing draw ratio. The applied elongational gradient orients the polymer chains and the clay particles along the spinning direction. When the applied flow results in the formation and the orientation of exfoliated nanoparticles, a pronounced increase of the mechanical properties is observed. The dispersed clay particles can be broken and oriented by the extensional flow, which might indicate a flow induced intercalated/exfoliated morphology transition.

The rheological response of a polyethylene/clay nanocomposite to annealing treatment under air and nitrogen atmospheres was studied. The treatment influences the rheology of the nanocomposite significantly. In particular, the viscosity and the non-Newtonian behavior dramatically increase with annealing time, and a liquid-like/solid-like transition is observed. The annealed samples were characterized by ATR-FT-IR spectrometry and it was shown that a silicate-rich layer is formed on the surface of the nanocomposite. This result was confirmed by TEM images of bulk and surface of annealed samples. It was demonstrated that the formation of this coating is the main cause of the change of rheological behavior.

Zinc oxide (ZnO) nanoparticles functionalized with a bi-functional coupling agent methacryloxypropyl-trimethoxysilane (MPS) were used to fabricate a vinyl-ester resin polymeric nanocomposite, which shows an improved interfacial interaction between the particle and matrix. As a result, in comparison to the unmodified particle-filled nanocomposites, the functionalized particle-filled composites possessed higher resistance to thermal degradation, and demonstrated improved UV shielding and enhanced photoluminescent properties. The more uniform particle dispersion, passivation of the particle surface with MPS and increased oxygen vacancies were justified to contribute to the increased thermal stability and the enhanced photoluminescent properties. Significant tensile strength improvement was closely related to the observed uniform particle distribution and the intimate interfacial interaction through the strong chemical bonding.

Mechanical recycling is an easy and economic way to re-use plastic waste as secondary materials, but, in general, their properties are worse with respect to the reclaimed materials and the virgin polymer. The aim of this work was to study the effect of concentration and reaction kinetics of two additives, an ethylene-co-glycidyl methacrylate (Lotader) and a hydroxylamine derivative (CGX), in the re-building of a degraded polyethylene. CGX is a nitroxyl radical generator able to form branching in polyolefins while the epoxy groups of Lotader can react with the functional groups present in the recycled polyethylene. The results indicate that the CGX has a higher reaction rate than Lotader, probably due to its lower molecular weight and the different reaction path. As for the effect of concentration, as expected, a higher amount of additive accelerates and increases re-building, especially when CGX is used. The melt strength increases with the additive content and the mechanical properties show a significant reduction at the highest concentrations of both additives due to excessive cross-linking.

Poly(butylene terephthalate) (PBT) and a sample of polyamide have been melt processed in the presence of two new phosphazene compounds, namely 2,2-dichloro-4,4,6,6-bis[spiro(2′,2″dioxy-1′,1″biphenyl)]cyclotriphosphazene (2Cl-CP) and 2,2-bis-(2-methoxy-4-methyleneoxy-phenoxy)-4,4,6,6,-bis[spiro(2′,2″dioxy-1′,1″biphenyl)]cyclophosphazene (CP-2EPOX). The blends were prepared by using polyamide 6 (PA6) at 25/75 w/w and 75/25 w/w composition. In order to perform a preliminary analysis on the behaviour of the blends, the materials were prepared in a batch mixer. The materials have been completely characterized from a rheological, morphological, mechanical point of view. The results indicate that the additives used cause an increase of the rupture properties and of the viscosity especially in the PA-rich blend. This result can be attributed to a chain extension effect on the PA phase, even if some compatibilisation with the formation of PBT/PA6 copolymers cannot be excluded as evidenced by the reduction of particle dimensions and by the improvement of the adhesion between the phases. Between the two compatibilisers, the CP-2EPOX displays the best results for both the investigated compositions while 2Cl-CP seems to act simply as a PA6 chain extender with very low compatibilising effect.

In this paper we present the synthesis and the characterization of cyclophosphazenes substituted with allyl groups, their transformation in epoxide-containing cyclophosphazenes and the final utilization of these compounds as chain extenders in combination with polyamides. The reaction at high temperature of Nylon-6 with epoxy-functionalized cyclophosphazenes leads to the opening of the epoxy units by the action of both amino (--NH2) and carboxylic (--COOH) end-groups of the polymer to enhance the final molecular weight of this material. The consequences of this fact on the thermal, mechanical and visco-elastic properties of treated Nylon-6 have been also evaluated and compared to those of the pristine material. Possible utilization of these cyclophosphazenes in recycling processes for degraded polyamides could be envisaged.

It is a common industrial practice to blend virgin polymer with the same recycled polymer coming from plastic scraps that, in general, has not undergone relevant degradation. In this work, the characteristics of blends of virgin and recycled polyamide have been considered by changing the amount of recycled polymer and the presence of humidity and a stabilizer. Neither dry nor wet stabilized recycled polyamide samples show significant variations of the molecular weight, but the melt Newtonian viscosity of the blends are slightly different from that predicted by an additive rule, despite the same chemical nature of the two components. This holds true even more for the humid unstabilized sample, as its noticeably lower molecular weight implies values lower than those expected on a linearity basis. The situation is different for the mechanical properties; here the morphology reached in the solid state determines a more rigid and brittle material, compared to the pure components, with relevant deviations from linearity for all the recycled samples used to prepare the blends. A different crystallinity as a function of the composition can be invoked to explain this phenomenon. The blends containing dry and wet stabilized recycled polyamide show almost the same behavior, confirming the reduced degradation of these samples.

Recycling of polycondensation polymers can give rise to secondary materials with good mechanical properties only if a careful drying is carried out before the melt reprocessing operations. The presence of humidity provokes the hydrolytic chain scission of the macromolecules and the consequent decrease of molecular weight and properties. In this work, the drying step was substituted by the addition of an antioxidant that is able to protect the macromolecules because it is the autioxidant is more prone to hydrolysis, thus removing the water from the melt. The mechanical properties of polyamide 6 reprocessed more times in wet conditions and in the presence of this stabilizer are even better than those obtained reprocessing the dry polyamide. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1899–1903, 2002

Polyamide (PA) and acrylonitrile/butadiene/styrene copolymer (ABS) may appear as a mixture in the recycled plastic stream. The incompatibility of these blends results in a blend with poor mechanical properties. The aim of this work is to partially convert the nitrile groups of the acrylonitrile/styrene copolymer (SAN) into oxazoline groups by reaction with aminoethanol (AE). Such modified SAN (SAN-m) can react with the amine or carboxylic acid end groups of PA, and therefore used as compatibilizers for blends of PA with ABS. SAN-m was found to reduce the SAN-domain size in the PA/SAN-blends. The initial acrylonitrile content of SAN-m had a strong influence on the degree of conversion into oxazoline groups and on the compatibilizing effect. Mechanical properties of SAN-m compatibilized PA/ABS blends were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 449–455, 2002

A new starch-based polymeric system, ZI1OU from Novamont, mainly composed of starch and polycaprolactone, was reprocessed several times in an extruder to investigate the recyclability of this biodegradable polymer. A previous investigation of the thermomechanical degradation in a mixer has been also done. The degradation is mostly due to the thermal stress but the presence of the mechanical stress strongly increases the degradation kinetic. During melt processing two concurrent processes take place: the first is the degradation, i.e. the breaking and shortening of polymeric chains, mostly occurring in the PCL phase; the second is the formation of some crosslinked structure in the starch phase. The rheological and mechanical properties, measured on samples subjected to repetitive extrusion operations carried out in a single screw extruder, clearly indicate that, in the adopted processing conditions, no significant modifications are observed. Only after five extrusions some decrease of these properties was measured.

The effect of the compounding method on the morphology and on the properties of poly(lactic acid) (PLA)-hydrotalcite (HT) composites was studied. Moreover, the influence of two different kinds of HT - organically modified (OM-HT) and unmodified (U-HT) - and their concentration was evaluated. The composites were prepared using either a single screw extruder (SSE), a counter rotating twin-screw compounder (TSC) or a corotating twin-screw extruder (TSE). The prepared materials were characterized by scanning electron microscopy, gel permeation chromatography (GPC) analysis, mechanical and rheological measurements. The results indicated that the best morphology, i.e., particles dimension and distribution, is exhibited by materials prepared by TSE while the worse ones by the samples processed by SSE. The viscosity of all the materials containing the HT is lower in comparison with the viscosity exhibited by the neat matrix, in particular, when the OM-HT is used. These results were correlated to degradation phenomena occurring during the processing of the materials as revealed by the results of GPC analysis. The addition of HT caused only a slight increase of elastic modulus of filled materials even when 5% of filler was incorporated. However, in full agreement with morphological analyses, the best performances were exhibited by materials prepared by TSE while the worse ones by the samples processed by SSE. POLYM. ENG. SCI., 54:1804-1810, 2014. © 2013 Society of Plastics Engineers.

The compatibilization of blends of polyamide-6 (PA6) with linear low density polyethylene (LLDPE) and of poly(ethylene terephthalate) (PET) with high density polyethylene (HDPE), by functionalization of the polyethylenes with oxazoline groups was investigated. Chemical modification of LLDPE and HDPE was carried out by melt free radical grafting with ricinoloxazoline maleinate. Blends preparation was made either with a two-steps procedure comprising functionalization and blending, and in a single step in which the chemical modification of polyethylene with the oxazoline monomer was realized in situ, during blending. The characterization of the products was carried out by FTIR spectroscopy and scanning electron microscopy (SEM). The rheological and mechanical properties of the blends were also investigated. The results show that functionalization of the polyethylenes can be achieved by melt blending with ricinoloxazoline maleinate even in the absence of free radical initiators. The compatibilization of the blends enhances the dispersion of the minor phase significantly, increases the melt viscosity, and improves the mechanical properties. The one-step preparation of the compatibilized blends was also found to be effective, and is thought to be even more promising in view of commercial application.

The compatibilization mechanism of some compatibilizers for blends of polyolefins with a liquid crystalline polymer (LCP) was studied. Polyethylene (PE) and polypropylene (PP) were blended with a semirigid LCP (SBH) in a batch mixer, either with and without compatibilizers. The latter were two commercially available samples of functionalized polyolefins, that is, a PE-g-MA (HDM) and a PP-g-AA (Polybond 1001) copolymer and some purposely synthesized PE-g-LCP and PP-g-LCP copolymers. Microtomed films of the binary and the ternary blends were annealed at 240°C on the hot stage of a polarizing microscope and the changes undergone by their morphology were recorded as a function of time. The results indicate that the compatibilizers lower the interfacial tension, thereby providing an improvement of the minor phase dispersion. In addition to this, the rate of the coalescence caused by the high-temperature treatment is appreciably reduced in the systems compatibilized with the PE-SBH and PP-SBH graft copolymers. Among the commercial compatibilizers, only Polybond 1001 displayed an effect comparable to that of the above copolymers. HDM improved the morphology of the as-prepared PE blends, but failed to grant sufficient morphological stabilization against annealing-induced coarsening. The results are discussed with reference to the chemical structure of the different compatibilizers.

Oxazoline is a very interesting functionality for reactive extrusion and other applications. In this paper, we report the possibility of chemically transforming nitrile group attached to a copolymer of styrene and acrylonitrile (SAN) to oxazoline group using 2-amino-ethanol (AE). The chemical modification of SAN with AE was done in the molten state. Among various catalysts tested, zinc acetate turned out to be the most efficient. The effects of the catalyst concentration, temperature and mixing on the overall kinetics were studied. The formation of the expected oxazoline functionality was confirmed by infrared spectroscopy and by reacting with 1-naphthylacetic acid. The reaction between the oxazoline and the acid was very rapid as it went to completion within 2 minutes in the melt at 180 degrees C. The efficiency of an oxazoline modified SAN as compatibilizing precursor was evaluated for SAN/PA 6 and SAN/PBT blends.

In this work, we studied the effect of the method of preparation and of reprocessing on the morphology and, con- sequently, on the physical properties of polyamide 6 (PA6)/ high density polyethylene (HDPE)-clay nanocomposite blends in the presence of different compatibilizers. In particular, the nanocomposites were obtained by melt mixing using a co- rotating twin screw extruder (E1). The blends thus obtained were re-extruded (E2) under the same operating conditions. Moreover, blends with the same final composition were produced using a masterbatch of the compatibilizer with the clay prepared in a separated stage in a batch mixer (MB). All the materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD) analyses. In addition, the rheological behaviour and the, tensile and impact, properties were evaluated. The XRD and TEM analysis showed that re-extrusion slightly improves the morphology of the nanocomposites. A further improvement of the morphology, in terms of lower clay dimension and better dispersion, was observed in the MB blends. The results of the mechanical tests showed that reprocess- ing (E2) induced an increase of all the properties for all the three systems. A further general increase of the mechanical properties was showed by the MB blends.

The increase of the interest in polymer nanocomposites has been leading to continuous growing search toward nanofillers alternative to the widely known clay-based ones. One of these possible alternatives is represented by calcium carbonate nanoparticles, which have not been widely investigated in such context. In this article, a study on the rheological and morphological behavior of dif- ferent low density polyethylene-calcium carbonate nanocomposites, compared with a reference calcium carbonate microcomposite, is presented. Several different nanosized calcium carbonates at different amounts were used. The results from the rheological and me- chanical tests outlined that only minor changes occur when the amount is up to 2 wt %. The use of higher filler concentrations or the increase in the processing time can significantly affect this behavior. SEM analysis allowed deeper understanding of these phenom- ena. V C 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 2544-2552, 2013

Fluoroelastomers (FEs) usually have working temperatures above 150°C and a great resistance to aggressive agents such as oils, fuels, aliphatic and aromatic solvents, steam, moderate acid, and basic environments. Liquid crystal polymers (LCPs) can be effective processing aids and reinforcing agents for elastomers. These characteristics are very attractive to lower melt viscosity and to stiffen and strengthen the final product through a simple blending. Among the LCPs, the semirigid LCPs seem the most appealing for blending with flexible thermoplastics (FTs) because their processing temperatures can be arranged to be in the same processing temperature range of FTs and because the presence of flexible segments can improve the compatibility with the flexible matrix. This is very important especially for FEs that are subjected not only to mechanical degradation, but also to thermal degradation. Blends of FEs with two types of semirigid LCPs show easy processability and enhanced mechanical and thermomechanical properties. These improvements were observed both for pure FEs and for filled vulcanized systems. The improvement of the mechanical properties is below that expected on the basis of the additive rule due to the incompatibility between the components; nevertheless, an impressive increase of the elastic modulus, up to 40 times, was noticed by adding 20% of LCP. In vulcanized systems, the tensile strength is also increased, whereas the elongation at break is slightly reduced. The working temperature is also drastically increased both in vulcanized and in unvulcanized systems. © 1996 John Wiley & Sons, Inc.

Semirigid liquid crystalline polymers (LCPs) show some advantages with respect to rigid LCP: in particular lower processing temperatures, better compatibility with flexible thermoplastics, but also some disadvantages. Thermal resistance of rigid LCPs is much better and the maximum working temperature is, in general, very high. The thermomechanical properties can be improved by adding inorganic fillers. In this work processing, mechanical and thermomechanical properties of a filled semirigid liquid crystal copolyester are reported. Several inorganic fillers have been used in order to put in evidence the influence of shape and dimensions of the particles on the properties of the filled materials. Both elastic modulus and tensile strength improve by increasing the filler content while the elongation at break decreases. The more eclatant improvement, however, arises from the creep and from thermomechanical behaviour. The creep rate is drastically reduced and the maximum working temperature is remarkably increased. The glass fibre filled polymer displays the best results. The only negative feature is the rise of the power necessary to process the material. Copyright (C) 1996 Elsevier Science Ltd

The photo-oxidative behaviour of different antimicrobial blown films based on poly (ethylene-co-vinyl acetate) (EVA) was studied. In particular, two samples of EVA containing different level of vinyl acetate comonomer (namely 14% and 28%) were used as matrices while nisin at different concentrations was used as antimicrobial agent. The degradation was followed by analyzing the changes in the spectroscopic behaviour and of the elongation at break measured in tensile tests. Moreover, changes in the antimicrobial activity of the films were followed by measuring the inhibition halo in agar diffusion tests. The results indicate that nisin acts as an excellent UV stabilizer for both samples of EVA used and especially for the sample with the higher vinyl acetate content. The protective effect of nisin is accompanied by a progressive decrease of the antimicrobial properties as a function of the photo-oxidation time due to the photo-degradation of the additive, which causes the inactivation of the additive.

Poly(ethylene terephthalate) (PET) is one of the most used commodity polymers, especially for food and beverage applications, and its recycling is of great importance because of the possible use in the textile and construction industries. On the other hand, the interest in biodegradable polymers has led, in recent years, to the use of materials such as poly(lactic acid) (PLA) also in the food and beverage industry. The presence of small amounts of PLA in the PET waste can significantly affect the post-consumer recycling process. In this work, the effect of the presence of small amounts of PLA on the recycling of PET bottles is investigated by rheological, mechanical, morphological and thermogravimetric analysis. The results indicate that this presence can significantly affect the rheological properties under non-isothermal elongational flow, while the mechanical properties were considerably affected only in some circumstances and the thermal stability was not significantly modified.

In this work, we present the results of a kinetic study of the surface modification of the carboxyl group of poly(ethylene-co-acrylic acid) into acyl chloride. Reaction temperature and time, concentration of the reactants, kind of agitation have been changed in order to understand their effect on the conversion. A study on the penetration of the reaction inside the sample bulk was also performed. The results indicate that, when short reaction times are adopted, the reaction limits to the outer layers of the samples and, in this case, on increasing the temperature, the concentration of the reactants and the stirring allows having a faster kinetic. At longer reaction times, the reaction penetrates deep inside the sample (several tens of microns) and the influence of the above mentioned variables on the kinetic is very low. The results, obtained by direct FTIR, ATR-FTIR, SEM–EDX and contact angle measurements, were confirmed and corroborated by theoretical estimations.