Poly(vinyl chloride) has been a key polymeric material since its commercial production in 1931, demonstrating versatility across numerous industries due to its compatibility with various additives. PVC's inherent properties, flame retardance, durability, and recyclability make it ideal for building and construction, which accounts for a significant portion of its consumption in Europe. This paper reviews the thermal degradation, decomposition, and combustion behavior of plasticized PVC, focusing mainly on classical stabilization systems and novel nanostructured additives such as polyhedral oligomeric silsesquioxane (POSS), which offer promising advances in improving PVC's thermal stability and fire performance. The review highlights how these aspects, mainly when addressed with innovative additives, could shape the future of PVC compounds in high-performance applications, especially in the cable industry, where fire performance and regulatory compliance are increasingly important.

This study evaluated the feasibility of mechanical recycling of plastic waste recovered from the disassembly of end-of-life lithium iron phosphate battery cases. In particular, the work focused on the case fraction, corresponding to the outer battery envelope, which represents the largest share of the plastic waste by weight. A preliminary characterization was carried out to determine the physico-chemical properties of the material and assess its suitability for mechanical recycling. The polymer matrix was found to consist of polypropylene, with glass fibers and calcium carbonate as inorganic fillers, each present at 18 wt%. X-ray fluorescence and elemental analysis confirmed the absence of elements of concern and subsequently, recycled material processability was investigated, with particular attention to injection molding, the same technology used to manufacture the original battery cases. Rheological analyses confirmed that the material exhibits Newtonian rheological behavior, suitable for injection molding, as also supported by a melt flow index value equal to 7.5 g/10 min (230 °C, 2.16 kg). The material was then reprocessed, and the resulting specimens were subjected to mechanical tests, with impact energy equal to 30.5 kJ/m2 and flexural strength amounting to 36.8 MPa. Overall, the recycled material exhibited adequate processability and mechanical performance after one reprocessing step, suggesting its potential for high-value mechanical recycling.

In this work, the influence of the elongational flow on the microstructure and the ductility of a poly(lactic acid)/ poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) blend was investigated. Anisotropic films were produced through cast extrusion and film blowing, and their morphology and mechanical properties were compared to those of an isotropic compression-molded sample. The results revealed that the application of the elongational flow is effective in inducing relevant modifications of the blend microstructure, passing from a droplet-matrix morphology for the isotropic sample to practically indistinguishable polymer phases in the anisotropic films. These processing-induced morphological alterations induced a brittle-to-ductile transition for both cast-extruded and blown films, which reached an elongation at break of 40 and 74 %, respectively.

This study explores the development of nanostructured flame-retardant systems using ethylene-butyl acrylate (EBA) copolymer and nanoclays. This was achieved following two strategies: namely, the incorporation of the nanofiller into the bulk material or its confinement to the surface through the utilization of coatings. First, the effectiveness of the bulk approach was evaluated. To this aim, 4 wt.% nanoclays were embedded within EBA, resulting in a 50% reduction in peak heat release rate and a significant delay in flame-out time when compared to the unfilled copolymer. Then, films containing 4 wt.% nanoclay with a thickness of 300 & micro;m produced via compression molding or cast extrusion, were applied as surface coatings to unfilled EBA substrates, yielding an overall clay content of 0.36 wt.% of the total sample. Despite the reduced nanoclay content, the surface confinement proved to be more effective than the bulk incorporation in delaying ignition time (an increase of 20% and 50% compared to the bulk nanocomposite and neat copolymer, respectively), suggesting more efficient initial protective action. Overall, the obtained results indicate that the nanoclay surface localization leads to slower fire propagation and improved fire safety while preserving polymer bulk properties.

Nanoplastics (NPs) are considered to be widespread environmental pollutants but little is known about their occurrence and properties in soils. Here, we evaluate and optimise an extraction and purification method for NPs in soil, aiming to preserve particle integrity and assess the potential for a single extraction workflow to support characterisation by both advanced microscopy techniques and mass-based techniques such as Py-GC-MS. This targets comprehensive characterisation of NPs, including size, shape, polymer chemistry, and mass concentration data. Individual extraction and purification steps were optimised, including density separation by centrifugation using a sucrose solution, filtration to < 1 μm by vacuum filtration and concentration combined with purification using direct flow ultrafiltration. Recovery tests using Pd-doped NPs aided baseline performance quantification. Recoveries were 38

In the framework of plastic circularity, managing end-of-life plastics containing flame-retardant (FR) additives represents a significant challenge. Although FRs are essential for enhancing fire safety in polymeric materials, many FR-containing products are never exposed to fire during their service life. As a result, substantial amounts of still-active FR remain in plastic waste streams. Since mechanical recycling is currently the most widely implemented strategy for plastic waste management, it is crucial to evaluate whether this process affects the flammability and combustion behavior of FR plastics. In this study, polypropylene (PP) containing 21 wt.% intumescent FR (IFR) was reprocessed up to five times to simulate mechanical recycling. After each cycle, the materials were systematically characterized in terms of rheological, morphological, combustion, and mechanical behavior. Although the agglomeration of IFR particles was observed after multiple cycles, the materials maintained stable processability and thermal stability. Importantly, the charring efficiency of the IFR system was preserved, resulting in consistent flammability performance; furthermore, all reprocessed samples achieved UL 94 V-0 classification and exhibited comparable limited oxygen index values. Mechanical properties were likewise largely maintained. Overall, these findings demonstrate that mechanical recycling represents a viable end-of-life strategy for this PP/IFR system, supporting its compatibility with circular material flow.

The increasing use of recycled polypropylene (rPP) in technical and outdoor applications requires strategies to limit photo-oxidative degradation while maintaining adequate performance after reprocessing. In this work, the photo-oxidative stability of rPP films was investigated under accelerated weathering conditions, focusing on the effect of a commercially available additive, Nexamite (R) R201 (NEX), previously shown to partially restore PP molecular weight after reprocessing. Films of rPP and rPP containing 5 wt.% NEX were produced by cast extrusion and exposed to cyclic UVA irradiation and water condensation in a QUV chamber, and the evolution of the functional and structural degradation of the materials was monitored as a function of aging time. Spectroscopical analyses showed progressive oxidation in both systems, with carbonyl growth starting after an induction period of about 200 h. A faster increase in the carbonyl index was observed for rPP containing NEX, indicating that the additive does not improve chemical oxidative resistance under the adopted conditions. However, NEX significantly enhanced the retention of mechanical properties during aging, with higher elongation and stress at break compared with unmodified rPP, thus delaying embrittlement. Overall, the results show that the investigated additive effectively mitigates the loss of mechanical integrity during photo-aging, likely as a consequence of the macromolecular restructuring induced during reprocessing.

In this study, the performance of an intumescent flame-retardant (IFR) system in recycled polypropylene (PP) was investigated. To this aim, virgin and reprocessed PPs were melt-compounded with 21 wt % of an IFR consisting of piperazine pyrophosphate (PAPP) and melamine polyphosphate (MPP) (2:1 ratio), and the obtained materials were characterized in terms of morphology and rheological and combustion behavior. Cone calorimetry results showed that although both IFR-containing materials exhibited a similar reduction in heat release rate as compared to the unfilled matrices, the recycled PP-based system displayed a higher time to ignition and a pronounced delay in the second heat release rate peak. The observed behavior was explained by considering the formation of a more compact and denser char, likely promoted by the finer dispersion of IFR particles achieved in the low-viscosity recycled PP matrix. Furthermore, both materials achieved a V-0 rating in UL-94 testing and comparable LOI values. Finally, the assessment of the mechanical behavior of both systems demonstrated that the utilization of recycled PP does not compromise the tensile and flexural strength of the material, notwithstanding a slight decrease in ductility as compared to the virgin PP-based counterpart. Overall, these findings demonstrate that recycled PP can be effectively used in flame-retardant formulations, broadening its potential applications while reducing dependence on virgin materials and supporting the development of circular economy approaches.

Nonwoven waste from new or postuse surgical and FFP2 face masks represents a complex multimaterial stream with significant upcycling potential. Material characterization identified PP and PE as the predominant components, with minor fractions of PET, cellulose fibers, and inorganic fillers. Rheology was used to classify different waste streams: postuse surgical masks exhibited low viscosity and negligible yield stress, making it suitable for injection molding; postuse FFP2 masks showed higher zero-shear viscosity, pronounced shear-thinning, and significant yield stress, ensuring filament stability and shape retention in material extrusion additive manufacturing; new surgical masks displayed intermediate viscosity and shear-thinning, enabling smooth and anisotropic film production via extrusion. Blending strategies of postuse masks enabled tuning of rheological and mechanical properties: injection-molded samples maintained homogeneous mechanical performances within similar to 20% deviation, while 3D-printed blends exhibited surface roundness and roughness associated with postuse FFP2 content. Overall, mask-derived nonwovens can be successfully upcycled into sustainable feedstock.

Using additive manufacturing for the design of inserts in injection moulding (IM) offers advantages in product development and customization. However, challenges related to operating temperature and mechanical resistance remain. This article presents a systematic screening methodology to evaluate the suitability of materials for specific applications. Ten commercial Material Extrusion (MEX) filaments were selected to produce test samples. Moldex3D simulation software was employed to model the IM process using two thermoplastics and to determine the temperature and pressure conditions that the printed inserts must withstand. Simulation results were critically interpreted and cross-referenced with the experimental material characterisations to evaluate material suitability. Nine of the ten MEX materials were suitable for IM with LDPE, and five with PP. Dimensional assessments revealed that six insert solutions required further post-processing for assembly, while three did not. All of the selected materials successfully survived 10 injection cycles without encountering any significant issues. The simulation results were validated by comparing temperature data from a thermal imaging camera during IM, revealing only minor deviations. The study concludes that combining targeted material characterization with CAE simulation provides an effective and low-cost strategy for selecting MEX filaments for injection moulding inserts, supporting rapid tooling applications in niche production.

This work proposes a coating approach for obtaining flame-retardant ethylene-vinyl acetate (EVA) and ethylene-butyl acrylate (EBA) copolymer-based materials. Nanocomposite films of EVA and EBA were first produced by cast extrusion, with two types of layered double hydroxides (LDHs) differing in the aspect ratio used as nanofillers. Subsequently, the films were applied as a coating to the corresponding neat copolymer substrate, and the combustion behavior of the so-obtained samples was evaluated through cone calorimeter tests. Despite the small amount of nanofillers (0.5 wt.% considering the whole specimen), the application of the coatings significantly improved the time to ignition compared to the pristine copolymers, while the shape of the heat release rate curves and the relative peak values remained relatively unchanged. The effect of the embedded nanofillers in delaying the ignition was more effective for the EVA-based systems than for the EBA ones (showing an increment of 30% and 12%, respectively, compared to the uncoated samples), likely due to the more homogeneous dispersion of the LDHs obtained in the first case. The obtained results demonstrate the effectiveness of the coating approach, since it allows the flame-retardant action to be concentrated on the surface of a polymer system, where combustion specifically takes place, while minimizing the required amount of flame retardant.

This study investigates the dual functionality of Tannic Acid (TA), a bio-derived polyphenol, as a surface modifier for ultra-high molecular weight polyethylene (UHMWPE) fibers and as a hardener for diglycidyl ether of bisphenol A (DGEBA) epoxy resin, aimed at enhancing composite laminate performance and sustainability. The surface characteristics of UHMWPE fibers were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The TA-modified fibers exhibited functional groups that enhanced their polarity and improved their compatibility with the epoxy matrix. Furthermore, thermogravimetric analysis revealed an increase in thermal degradation onset from 336 degrees C to 357 degrees C after TA treatment. The hand lay-up method was used to manufacture composite UHMWPE laminates impregnated with TA-hardened resins at different TA concentrations. Cone calorimetry results revealed improved fire resistance for TA-loaded composites, with a 44% reduction in peak heat release rate (PHRR) respect to the control sample, as well as a better fire performance index. Composite laminates manufactured with TA-modified fibers and TA-hardened resin demonstrated up to 45% improvement in tensile strength.Highlights Tannic acid (TA) proves to be a sustainable alternative to petroleum-based hardeners. TA enhances UHMWPE fibers' thermal stability and adhesion to epoxy. TA-modified fibers show an increase in thermal degradation onset. TA-hardening of epoxy improves fire resistance, reducing PHRR by 44%. Composite laminates with TA show a 45% increase in tensile strength.

In the context of polymer-based composites, the knowledge of the correlations between the processing conditions, the microstructure, and the final properties is essential to tailor polymeric systems for specific applications. Specifically concerning the extrusion process, an accurate design of the screw profile allows for achieving composites with modulable microstructures, according to the specific properties required by the intended application. In this work, films of polylactic acid-based composites with 5 wt.% of talc were obtained by means of a single-screw extruder equipped with a flat die and a calender unit. Three different screw profiles, namely a general-purpose compression screw, a screw with a reverse flow zone, and a barrier screw, were employed for the production of films. The ability of the screw profile in varying the degree of filler dispersion and distribution was assessed through morphological and rheological analyses, demonstrating that the barrier screw is more able in disaggregating the talc lamellae. Due to the achieved microstructures, films produced using this screw profile exhibited superior barrier properties, with a decrease of about 27% in the oxygen permeability as compared to unfilled PLA. However, a concurrent decrease in material ductility as compared to the other films was observed. Finally, the thermoformability of the composites was assessed; also in this case, trays with more precise edges and corners were obtained for the film formulated through the barrier screw.

In this work, the relationships between the processing parameters and the microstructure in melt-compounded polyamide 6 (PA6) are investigated. To this aim, two PA6 having different viscosities are processed in a twin-screw extruder at two different screw speeds (150 or 300 rpm) and characterized through rheological and thermal analyses. Furthermore, the thermo-mechanical field along the screw is simulated using Ludovic (R) software, and the obtained results in terms of shear rate, residence time, and actual temperature are exploited to disclose interesting processing/microstructure relationships. In particular, the antagonistic role of the flow-induced crystallization (FIC) and memory effect in governing the final microstructure is assessed. Specifically, for high screw speed and viscosity, FIC outweighs the memory effect due to the higher shear rate and temperature experienced by the material during processing. Besides, the dominant influence of FIC over the memory effect is found to be responsible for the higher overall crystallinity and alpha/gamma content observed for the materials processed at 300 rpm. Finally, the same analyses are performed on blends containing different relative contents of the two PA6, demonstrating the interdependency of the screw speed and viscosity effects on the resulting microstructure. Highlights Processing parameters/microstructurerelationships for PA6 are investigated. PA6 with different viscosities wasmelt compounded using two screw speeds. Shear rate, temperature and residencetime during the processing were simulated. Screw speed and viscosity affectflow-induced crystallization and memory effect. High screw speed and viscositypromoted FIC over the memory effect.

The mechanical recycling of thermoplastics (especially of polyolefins) often results in recyclates with inferior properties compared to their virgin counterparts. This phenomenon is mainly due to the modification of the polymer microstructure induced by the degradation processes undergone by the materials during their service life and reprocessing. In this work, a promising route for obtaining high-melt-strength recycled high-density polyethylene (HDPE) is proposed. In particular, the exploited approach involves the utilization of a commercially available additive (i.e., Nexamite® R305, Nexam Chemical, Lomma, Sweden), which was demonstrated to be capable of driving thermo-mechanical degradation reactions (experienced by HDPE during mechanical recycling) towards the obtainment of a long-chain branched microstructure, thereby enabling the further processing of the recycled material through technologies dominated by elongational flow. The additive-induced alterations of the polymer microstructure were exploited for the formulation of fibers, and the performed tensile characterization showed that the additive-containing material exhibits strikingly improved ductility (namely, elongation at break of 350% for the fibers stretched at a draw ratio of 60) with respect to pristine recycled HDPE. Overall, the obtained results clearly demonstrated the possibility of attaining an effective upcycling of HDPE, which could be exploited for industrially relevant high-added-value applications, hence paving the way for the achievement of full plastic circularity.

In this work, polypropylene (PP)-based filaments for Fused Filament Fabrication (FFF) containing boron nitride (BN) and talc (T) were developed, aiming at formulating multi-material 3D printed parts showing thermal conductivity and balanced mechanical properties. Particularly, skin-core structures obtained by localizing BN in the surface layers while confining T in the core were 3D printed and characterized, and their properties were compared to those of correspondent mono-material samples. The characterization of the PP/BN mono-material samples revealed a crucial role of the FFF process in inducing higher thermal conductivity in the radial direction of the specimens as compared to the axial one, owing to the preferential alignment of the fillers along the printing direction allowing the creation of continuous conductive paths in the in-plane direction. For the multi-material structures, it was demonstrated that confining the thermally conductive fillers to the surface of the samples allows achieving higher in-plane thermal conductivity as compared to PP/BN samples; for instance, nearly doubled values were obtained by decreasing the number of BN-containing layers from 15 to 3. Most importantly, the skin-core structures exhibit tensile modulus and stress practically identical to those of PP/T mono-material samples, despite the lower content of the reinforcing filler and the presence of interfaces between the two different composites.

In this work, a coating approach for obtaining flame-retardant EVA (Ethylene–Vinyl Acetate) and EBA (Ethylene–Butyl Acrylate) copolymer-based materials is proposed [...]

Despite growing interest in additive manufacturing for polymers, its industrial application is limited by a lack of suitable materials [...]

Polymer structuring is a valuable cost- and time-saving strategy for the production of high-performance polymer-based materials. The main issue in the spreading of this approach lies in the understanding of the relationships between the processing parameters, the microstructure and the resulting properties, which represent fundamental factors in the actual defining of the final characteristics owing to the production method employed. The aim of the present work is to provide a wide overview of the currently available knowledge on solvent-free approaches for obtaining structured materials, specifically focusing on extrusion- and injection molding-based technologies, given their relevance as the most industrially exploited methods for the melt processing of thermoplastic materials. Additionally, particular attention will be paid to the relationships between the variation in the processing parameters and the resulting flow fields (both shear and elongational), considering their role in the definition of microstructure.

Achieving effective mechanical recycling strategies for polyolefins remains a major challenge for several reasons. Firstly, the thermo-mechanical degradation underwent during reprocessing, as well as the different degradation forms experienced during the service life, cause a severe modification of polyolefin microstructure, ultimately leading to a progressive deterioration of their performance. On the other hand, due to non-fully accurate sorting technologies, low levels of cross-contamination are commonly encountered in recycled polyolefins. All these features result in the obtainment recyclates with a heterogeneous and complex morphology, which significantly affects their final properties, often limiting their possible future applications. This work aims at addressing these issues, evaluating the combined effect of cross-contamination and of the degradation undergone by the polymers during service life and reprocessing for high-density polyethylene (HDPE) containing low amounts of polypropylene (PP) and polyethylene terephthalate (PET) as contaminants. In particular, pristine and crosscontaminated HDPE were subjected to photo-oxidative or thermo-oxidative treatments and the aged materials were reprocessed, aiming at simulating the real conditions of a typical mechanical recycling process. The obtained results demonstrated that cross-contamination minimises the functional degradation of HDPE, especially under photo-oxidative conditions. Conversely, the microstructural characterization pointed out that different microstructures can be achieved depending on the level of cross-contamination and on the aging treatment. Finally, it was shown that the presence of PP and PET as contaminants has a detrimental impact on the HDPE ductility, especially under thermo-oxidative conditions, while for photo-oxidised materials exerts a marginal role.