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Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a highly promising biodegradable and bio-based thermoplastic recognized for its environmental benefits and potential versatility. However, its industrial adoption has been limited due to its inherent brittleness and suboptimal processability. Despite these challenges, PHBV's performance can be tailored for a wide range of applications through strategic modifications, particularly by blending it with other biodegradable polymers or reinforcing it with natural fibers and bio-based fillers. This study explores the potential of brewers' spent grain (BSG) as a sustainable source for the development of PHBV biocomposites. The biocomposites were synthesized by incorporating arabinoxylan-bound benzoate, which can be derived from BSG, as a sustainable filler at concentrations of 4% and 10% w/w. The resulting materials were characterized using tensile testing, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The findings demonstrate that the incorporation of functionalized arabinoxylan significantly enhances the mechanical properties of PHBV, preserves its thermal stability, and increases its crystallinity (from 59.9% to 67.6%), highlighting a positive impact on both material performance and processing characteristics. [ABSTRACT FROM AUTHOR] more...

Cleavable bio-based epoxy resin systems are emerging, eco-friendly, and promising alternatives to the common thermoset ones, providing quite comparable thermo-mechanical properties while enabling a circular and green end-of-life scenario of the composite materials. In addition to being designed to incorporate a bio-based resin greener than the conventional fully fossil-based epoxies, these formulations involve cleaving hardeners that enable, under mild thermo-chemical conditions, the total recycling of the composite material through the recovery of the fiber and matrix as a thermoplastic. This research addressed the characterization, processability, and recyclability of a new commercial cleavable bio-resin formulation (designed by the R-Concept company) that can be used in the fabrication of fully recyclable polymer composites. The resin was first studied to investigate the influence of the different post-curing regimes (room temperature, 100 °C, and 140 °C) on its thermal stability and glass transition temperature. According to the results obtained, the non-post-cured resin displayed the highest Tg (i.e., 76.6 °C). The same post-curing treatments were also probed on the composite laminates (glass and carbon) produced via a lab-scale vacuum-assisted resin transfer molding system, evaluating flexural behavior, microstructure, and dynamic-mechanical characteristics. The post-curing at 100 °C would enhance the crosslinking of polymer chains, improving the mechanical strength of composites. With respect to the non-post-cured laminates, the flexural strength improved by 3% and 12% in carbon and glass-based composites, respectively. The post-curing at 140 °C was instead detrimental to the mechanical performance. Finally, on the laminates produced, a chemical recycling procedure was implemented, demonstrating the feasibility of recovering both thermoplastic-based resin and fibers. [ABSTRACT FROM AUTHOR] more...

In this work, five different dextran-based cryogels for controlled drug release are investigated. Vitamin B12 was used as a model drug for in vitro release tests. Two different drug-loading procedures were adopted, leading to very different drug release curves. Indeed, a fast Fickian release was observed when freeze-dried samples of DEX40PEG360MA and DEX40PEG500MA were infused with the drug after cryogel formation. On the contrary, a slowed highly non-Fickian behavior arises when the drug is loaded before the low-temperature crosslinking step, leading to the cryogel formation. The non-Fickian drug release, observed for all the five different dextran-based cryogels investigated, is actually due to the cryoconcentration phenomenon, modeled with a two-step release process. The proposed transport model accurately predicts experimental release curves characterized by a long lag time, confirming that dextran-based cryogels are suitable for controlled release. [ABSTRACT FROM AUTHOR] more...

Cryogels represent a valid strategy as scaffolds for tissue engineering. In order to adequately support adhesion and proliferation of anchorage-dependent cells, different polymers need to be combined within the same scaffold trying to mimic the complex features of a natural extracellular matrix (ECM). For this reason, in this work, gelatin (Gel) and chondroitin sulfate (CS), both functionalized with methacrylic groups to produce CSMA and GelMA derivatives, were selected to prepare cryogel networks. Both homopolymer and heteropolymer cryogels were produced, via radical crosslinking reactions carried out at −12 °C for 2 h. All the scaffolds were characterized for their mechanical, swelling and morphological properties, before and after autoclave sterilization. Moreover, they were evaluated for their biocompatibility and ability to support the adhesion of human gingival fibroblasts and tenocytes. GelMA-based homopolymer networks better withstood the autoclave sterilization process, compared to CSMA cryogels. Indeed, GelMA cryogels showed a decrease in stiffness of approximately 30%, whereas CSMA cryogels of approximately 80%. When GelMA and CSMA were blended in the same network, an intermediate outcome was observed. However, the hybrid scaffolds showed a general worsening of the biological performance. Indeed, despite their ability to withstand autoclave sterilization with limited modification of the mechanical and morphological properties, the hybrid cryogels exhibited poor cell adhesion and high LDH leakage. Therefore, not only do network components need to be properly selected, but also their combination and ability to withstand effective sterilization process should be carefully evaluated for the development of efficient scaffolds designed for tissue engineering purposes. [ABSTRACT FROM AUTHOR] more...

The present study examined the effect of biobased molecules grafted onto wrapped flax rovings on the mechanical properties of fabrics designed for epoxy-based biocomposites, aiming to optimize fiber/matrix adhesion. Biobased solutions, such as tannins from quebracho, were used to treat wrapped flax rovings in comparison to a non-biobased aminosilane solution used as a reference. The chemical treatment is performed using an innovative lab-scale impregnation line. The influence of the solution concentration has been investigated. SEM-EDX and FT-IR confirmed the grafting efficiency of molecules on wrapped rovings. Plain and 5-harness satin fabrics were then manufactured at lab scale with the resulting functionalized rovings. Tensile tests were carried out on rovings and on fabrics. A concentration of 1% silane is sufficient to improve the mechanical properties of rovings and fabrics. The addition of NaOH to tannins strengthens flax fiber rovings more than tannins alone, and the weave pattern influences mechanical performance. [ABSTRACT FROM AUTHOR] more...

Fused Deposition Modeling (FDM) enables many advantages compared to traditional manufacturing techniques, but the lower mechanical performance due to the higher porosity still hinders its industrial spread in key sectors like the automotive industry. PP and PA12 filaments filled with low amounts of basalt fibers were produced in the present work to improve the poor mechanical properties inherited from the additive manufacturing technique. For both matrices, the introduction of 5 wt.% of basalt fibers allows us to achieve stiffness values comparable to injection molding ones without modifying the final weight of the manufactured components. The increased filament density compared with the neat polymers, upon the introduction of basalt fibers, is counterbalanced by the intrinsic porosity of the manufacturing technique. In particular, the final components are characterized by a 0.88 g/cm3 density for PP and 1.01 g/cm3 for PA12 basalt-filled composites, which are comparable to the 0.91 g/cm3 and 1.01 g/cm3, respectively, of the related neat matrix used in injection molding. Some efforts are still needed to fill the gap of 15–28% for PP and of 26.5% for PA12 in tensile strength compared to injection-molded counterparts, but the improvement of the fiber/matrix interface by fiber surface modification or coupling agent employment could be a feasible solution. [ABSTRACT FROM AUTHOR] more...

With a view to achieving sustainable development and a circular economy, this work focused on the possibility to valorize a secondary waste stream of recycled carbon fiber (rCF) to produce a 3D printing usable material with a PA6,6 polymer matrix. The reinforcing fibers implemented in the research are the result of a double-recovery action: starting with pyrolysis, long fibers are obtained, which are used to produce non-woven fabrics, and subsequently, fiber agglomerate wastes obtained from this last process are ground in a ball mill. The effect of different amounts of reinforcement at 5% and 10% by weight on the mechanical properties of 3D-printed thermoplastic composites was investigated. Although the recycled fraction was successfully integrated in the production of filaments for 3D printing and therefore in the production of specimens via the fused deposition modeling technique, the results showed that fibers did not improve the mechanical properties as expected, due to an unsuitable average size distribution and the presence of a predominant dusty fraction ascribed to the non-optimized ball milling process. PA6,6 + 10 wt.% rCF composites exhibited a tensile strength of 59.53 MPa and a tensile modulus of 2.24 GPa, which correspond to an improvement in mechanical behavior of 5% and 21% compared to the neat PA6,6 specimens, respectively. The printed composite specimens loaded with the lowest content of rCF provided the greatest improvement in strength (+9% over the neat sample). Next, a prediction of the "optimum" critical length of carbon fibers was proposed that could be used for future optimization of recycled fiber processing. [ABSTRACT FROM AUTHOR] more...

The transportation sector is striving to meet the more severe European legislation which encourages all industrial fields to embrace more eco-friendly policies by exploiting constituents from renewable resources. In this framework, the present work assessed the potential of a bio-based, low molecular weight PA11 matrix reinforced with flax and intraply flax/basalt hybrid fabrics. To this aim, both quasi-static and impact performance were addressed through three-point bending and low-velocity impact tests, respectively. For hybrid composites, the effect of stacking sequence, i.e., [0/0] and [0/90], and fiber orientation were considered, while the effect of temperature, i.e., −40 °C, room temperature and +45 °C, was investigated for laminates' impact response. The mechanical experimental campaign was supported by thermal and morphological analyses. The results disclosed an improved processability of the low molecular weight PA11, which ensured a manufacturing temperature of 200 °C, which is fundamental to minimize flax fibers' thermal degradation. Both quasi-static and impact properties demonstrated that hybridization is a good solution for obtaining good mechanical properties while preserving laminates' lightness and biodegradability. The [0/90] configuration proved to be the best solution, providing satisfying flexural performance, with an increase between 62% and 83% in stiffness and between 19.6% and 37.6% in strength compared to flax-based laminates, and the best impact performance, with a reduction in permanent indentation and back crack extent. [ABSTRACT FROM AUTHOR] more...

In this work, the use of a recycled mix stemming from the treatment of multilayer aseptic packaging used in the food and beverage industry is proposed as the matrix for short fibre composites reinforced with flax fibres, to generate value-added materials in contrast to the more common end-of-life scenario including energy recovery. This is expected to be a preferred choice in the waste hierarchy at the European level. A commercially available material (EcoAllene) obtained from multilayer packaging recycling was compounded with short flax fibres up to 30 wt.% by twin screw extrusion, with a view to enhancing its poor mechanical profile and broadening its applications. Composites were in depth analyzed by thermogravimetric analysis and differential scanning calorimetry, which highlighted the complex nature of this recycled product, a limited nucleation ability of flax fibres and a lower thermal stability due to the premature degradation of natural hemicellulose and cellulose, though featuring in any case onset degradation temperatures higher than 300 °C. Composites' mechanical properties were assessed in tension, bending and impact conditions, with remarkable improvements over the neat matrix in terms of stiffness and strength. In particular, at 30 wt.% fibre content and with 5 wt.% of maleated coupling agent, an increase in tensile and flexural strength values by 92% and 138% was achieved, respectively, without compromising the impact strength. The effectiveness of flax fibres confirmed by dynamo-mechanical analysis is beneficial to the exploitation of these composites in automotive interiors and outdoor decking applications. [ABSTRACT FROM AUTHOR] more...

The effect of four lignocellulosic waste fillers on the thermal and mechanical properties of biocomposites was investigated. Powdered licorice root, palm leaf, holm oak and willow fillers were melt compounded with polypropylene at two different weight contents, i.e., 10 and 30, and then injection molded. A commercially available maleated coupling agent was used to improve the filler/matrix interfacial adhesion at 5 wt.%. Composites were subjected to chemical (FTIR-ATR), thermal (TGA, DSC, DMA) and mechanical (tensile, bending and Charpy impact) analyses coupled with a morphological investigation by scanning electron microscopy. Although similarities among the different formulations were noted, holm oak fillers provided the best combination of thermal and mechanical performance. In particular, at 30 wt.% content with coupling agent, this composite formulation displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, of 28% and 110%, 58% and 111%, compared to neat PP, respectively. The results imply that all these lignocellulosic waste fillers can be used successfully as raw materials for biocomposites, with properties comparable to those featured by other natural fillers. [ABSTRACT FROM AUTHOR] more...

Metal 3D-printed parts are critical in industries such as biomedical, surgery, and prosthetics to create tailored components for patients, but the costs associated with traditional metal additive manufacturing (AM) techniques are typically prohibitive. To overcome this disadvantage, more cost-effective manufacturing processes are needed, and a good approach is to combine fused deposition modeling (FDM) with debinding-sintering processes. Furthermore, optimizing the printing parameters is required to improve material density and mechanical performance. The design of experiment (DoE) technique was used to evaluate the impact of three printing factors, namely nozzle temperature, layer thickness, and flow rate, on the tensile and bending properties of sintered 316L stainless steel in this study. Green and sintered samples were morphologically and physically characterized after printing, and the optimal printing settings were determined by statistical analysis, which included the surface response technique. The mechanical properties of the specimens increased as the flow rate and layer thickness increased and the nozzle temperature decreased. The optimized printing parameters for the ranges used in this study include 110% flow rate, 140 μm layer thickness, and 240 °C nozzle temperature, which resulted in sintered parts with a tensile strength of 513 MPa and an elongation at break of about 60%. [ABSTRACT FROM AUTHOR] more...

Hierarchical functionalization of flax fibers with ZnO nanostructures was achieved by electroless deposition to improve the interfacial adhesion between the natural fibers and synthetic matrix in composite materials. The structural, morphological, thermal and wetting properties of the pristine and ZnO-coated flax fibers were investigated. Thus, the ZnO-coated flax fabric discloses an apparent contact angle of ~140° immediately after the placement of a water droplet on its surface. An assessment of the interfacial adhesion at the yarn scale was also carried out on the flax yarns coated with ZnO nanostructures. Thus, after the ZnO functionalization process, no significant degradation of the tensile properties of the flax yarns occurs. Furthermore, the single yarn fragmentation tests revealed a notable increase in the interfacial adhesion with an epoxy matrix, reductions of 36% and 9% in debonding and critical length values being measured compared to those of the pristine flax yarns, respectively. The analysis of the fracture morphology by scanning electron microscopy and X-ray microtomography highlighted the positive role of ZnO nanostructures in restraining debonding phenomena at the flax fibers/epoxy resin matrix interphase. [ABSTRACT FROM AUTHOR] more...

The aim of this work was to optimize and characterize nanocomposite films based on gellan gum methacrylate (GG-MA) and silver nanoparticles (AgNPs) for application in the field of wound dressing. The films were produced using the solvent casting technique coupled with a photocuring process. The UV irradiation of GG-MA solutions containing glycerol as a plasticizer and different amounts of silver nitrate resulted in the concurrent crosslinking of the photocurable polymer and a reduction of Ag ions with consequent in situ generation of AgNPs. In the first part of the work, the composition of the films was optimized, varying the concentration of the different components, the GG-MA/glycerol and GG-MA/silver nitrate weight ratios as well as the volume of the film-forming mixture. Rheological analyses were performed on the starting solutions, whereas the obtained films were characterized for their mechanical properties. Colorimetric analyses and swelling studies were also performed in order to determine the AgNPs release and the water uptake capacity of the films. Finally, microbiological tests were carried out to evaluate the antimicrobial efficacy of the optimized films, in order to demonstrate their possible application as dressings for the treatment of infected hard-to-heal wounds, which is a demanding task for public healthcare. [ABSTRACT FROM AUTHOR] more...

The low-density polyethylene (LDPE)/aluminium mix obtained after the recovery of cellulose from multilayer aseptic packaging used in the food and beverage industry is generally destined for energy recovery. In this work we propose it as a matrix for value-added composite materials. A commercially available material (EcoAllene) obtained from multilayer packaging recycling was reinforced with short natural basalt fibres up to 30 wt.% by twin screw extrusion, aiming at improving the mechanical profile of such material and widening its applications. Thermal characterizations by thermogravimetric analysis and differential scanning calorimetry showed that the material is indeed a complex mixture of LDPE, HDPE, PP, and aluminium. Basalt fibres did not modify the melting and crystallization profile as well as the global degradation behaviour. Composites were then subjected to tensile, bending, Charpy impact tests and the fracture surfaces were investigated by scanning electron microscopy. Results highlighted a beneficial effect of basalt fibres to stiffness and strength in both loading conditions, with improvements by 107% and 162% for tensile and bending strength, respectively, which were linked also to a 45% enhancement of impact strength. This increased mechanical performance is promising for their use in automotive interiors and outdoor decking applications. [ABSTRACT FROM AUTHOR] more...

Featured Application: The development of hybrid metal/polymer filaments opens the possibility to expand metal 3D printing with investment costs accessible to small and medium enterprises. This will allow 3D printing of metal parts with the same approach used for desktop 3D printing, thus further democratizing the use of additive manufacturing in applications that cannot be fulfilled by polymeric 3D printing. The exploitation of mechanical properties and customization possibilities of 3D printed metal parts usually come at the cost of complex and expensive equipment. To address this issue, hybrid metal/polymer composite filaments have been studied allowing the printing of metal parts by using the standard Fused Filament Fabrication (FFF) approach. The resulting hybrid metal/polymer part, the so called "green", can then be transformed into a dense metal part using debinding and sintering cycles. In this work, we investigated the manufacturing and characterization of green and sintered parts obtained by FFF of two commercial hybrid metal/polymer filaments, i.e., the Ultrafuse 316L by BASF and the 17-4 PH by Markforged. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS) analyses of the mesostructure highlighted incomplete raster bonding and voids like those observed in conventional FFF-printed polymeric structures despite the sintering cycle. A significant role in the tensile properties was played by the building orientation, with samples printed flatwise featuring the highest mechanical properties, though lower than those achievable with standard metal additive manufacturing techniques. [ABSTRACT FROM AUTHOR] more...

The disposal of fibre reinforced composite materials is a problem widely debated in the literature. This work explores the ability to restore the mechanical properties of thermally conditioned basalt fibres through chemical treatments. Inorganic acid (HF) and alkaline (NaOH) treatments proved to be effective in regenerating the mechanical strength of recycled basalt fibres, with up to 94% recovery of the strength on treatment with NaOH. In particular, HF treatment proved to be less effective compared to NaOH, therefore pointing towards a more environmentally sustainable approach considering the disposal issues linked to the use of HF. Moreover, the strength regeneration was found to be dependent on the level of temperature experienced during the thermal treatment process, with decreasing effectiveness as a function of increasing temperature. SEM analysis of the fibres' lateral surfaces suggests that surface defects removal induced by the etching reaction is the mechanism controlling recovery of fibre mechanical properties. In addition, studies on the fracture toughness of the regenerated single fibres were carried out, using focussed ion beam (FIB) milling technique, to investigate whether any structural change in the bulk fibre occurred after thermal exposure and chemical regeneration. A significant increase in the fracture toughness for the regenerated fibres, in comparison with the as-received and heat-treated basalt ones, was measured. [ABSTRACT FROM AUTHOR] more...

The aim of this study was to assess the effects of commercially available and relatively inexpensive enzyme preparations based on endo 1,4-β-xylanase, pectinase and xyloglucanase on the thermal (TGA), morphological (SEM), chemical (FT-IR) and mechanical (single yarn tensile tests) properties of flax yarns. The preparation based on pectinase and xyloglucanase provided the best results, resulting in the effective removal of hydrophilic components such as hemicellulose and pectin, the individualization of yarns and increased thermal stability at the expense of a reduction in mechanical properties, depending on the treatment parameters. Single yarn fragmentation tests pointed out an improved interfacial adhesion after enzymatic treatment, with reduced debonding length values of 18% for an epoxy matrix and up to 36% for a vinylester resin compared to untreated flax yarns. [ABSTRACT FROM AUTHOR] more...

In recent years, fluoropolymers have found numerous applications in the architectural field because of their combination of mechanical-chemical resistance and high transparency. In the present work, commercial fluorinated polymers, such as perfluoro alkoxy (PFA) and ethylene tetrafluoroethylene copolymer (ETFE), have been evaluated for use as protective and transparent layers on monumental and archaeological sites (to preserve mosaics or frescoes) during the phases of restoration or maintenance outdoors. Considering this specific application, the present study was developed by evaluating the evolution of the mechanical (tensile, tear propagation resistance, and low-velocity impact tests) and chemical (FTIR and DSC analysis) properties of the films after accelerated UV aging. The results that were obtained demonstrated the high resistance capacity of the ETFE, which exhibits considerably higher elastic modulus and critical tear energy values than PFA films (1075.38 MPa and 131.70 N/mm for ETFE; 625.48 MPa and 59.06 N/mm for PFA). After aging, the samples exhibited only a slight reduction of about 5% in the elastic modulus for both polymers and 10% in the critical tear energy values for PFA. Furthermore, the differences in impact resistance after aging were limited for both polymers; however, the ETFE film showed higher peak force than the PFA films (82.95 N and 42.22 N, respectively). The results obtained demonstrated the high resistance capacity of ETFE films, making them the most suitable candidate for the considered application. [ABSTRACT FROM AUTHOR] more...

Cork, a natural material from renewable resources, is currently attracting increasing interest in different industrial fields because of its cellular structure and the presence of the flexible suberin as its main chemical component. In an agglomerated form, it proved to be a compelling product not only as a thermal and acoustic insulator, but also as core material in sandwich structures and as a liner or padding in energy absorbing equipment. From this perspective, the assessment of its compressive response is fundamental to ensure the right out-of-plane stiffness required to a core material and the proper crashworthiness in the safety devices. Considering the complex nature of cork and the resulting peculiar compressive response, the present review article provides an overview of this paramount property, assessing the main parameters (anisotropy, temperature, strain rate, etc.) and the peculiar features (near-zero Poisson's ratio and unique dimensional recovery) that characterize it in its natural state. Furthermore, considering its massive exploitation in the agglomerated form, the design parameters that allow its compressive behavior to be tailored and the operating parameters that can affect its crashworthiness were assessed, reporting some potential industrial applications. [ABSTRACT FROM AUTHOR] more...

A poly(urethane-acrylate) polymer (PUA) was synthesized, and a sufficiently high molecular weight starting from urethane-acrylate oligomer (UAO) was obtained. PUA was then loaded with two types of powdered ligno-cellulosic waste, namely from licorice root and palm leaf, in amounts of 1, 5 and 10%, and the obtained composites were chemically and mechanically characterized. FTIR analysis of final PUA synthesized used for the composite production confirmed the new bonds formed during the polymerization process. The degradation temperatures of the two types of waste used were in line with what observed in most common natural fibers with an onset at 270 °C for licorice waste, and at 290 °C for palm leaf one. The former was more abundant in cellulose (44% vs. 12% lignin), whilst the latter was richer in lignin (30% vs. 26% cellulose). In the composites, only a limited reduction of degradation temperature was observed for palm leaf waste addition and some dispersion issues are observed for licorice root, leading to fluctuating results. Tensile performance of the composites indicates some reduction with respect to the pure polymer in terms of tensile strength, though stabilizing between data with 5 and 10% filler. In contrast, Shore A hardness of both composites slightly increases with higher filler content, while in stiffness-driven applications licorice-based composites showed potential due to an increase up to 50% compared to neat PUA. In general terms, the fracture surfaces tend to become rougher with filler introduction, which indicates the need for optimizing interfacial adhesion. [ABSTRACT FROM AUTHOR] more...

A multidisciplinary protocol is proposed to monitor the preservation of fresh pumpkin samples (FP) using three commercial polymeric films: A made of biodegradable cellophane from regenerated cellulose pulp; B from corn starch, cassava and eucalyptus, C made of polylactic acid from corn starch, and a polyethylene film used as reference (REF). Chemical, mechanical and microbiological analyses were applied on packaging and fresh and packaged samples at different times. After an 11-day period, NMR spectroscopy results showed a sucrose increase and a malic acid decrease in all the biofilms with respect to FP; fructose, glucose, galactose levels remained quite constant in biofilms B and C; the most abundant amino acids remained quite constant in biofilm A and decreased significantly in biofilm B. From microbiological analyses total microbial count was below the threshold value up to 7 days for samples in all the films, and 11 days for biofilm C. The lactic acid bacteria, and yeasts and molds counts were below the acceptability limit during the 11 days for all packages. In the case of biofilm C, the most promising packaging for microbiological point of view, aroma analysis was also carried out. In this paper, you can find all the analysis performed and all the values found. [ABSTRACT FROM AUTHOR] more...

The composites based on basalt fibres and poly(lactic acid) (PLA) show promising applications in biomedical and automotive fields, but their mechanical performance is still largely hindered by poor interfacial properties. Zinc oxide nanorods have been successfully used to tune the PLA/basalt fibre interface by growing them on commercially available basalt fabrics. The hierarchical fibres significantly enhanced the mechanical properties of PLA-based composites, especially their flexural strength and stiffness. These values are 26% and 22% higher than those of unmodified basalt/PLA composites, and 24% and 34% higher than those of glass/PLA composites used as a baseline. The increase in tensile and flexural properties hinges on the mechanical interlocking action promoted by ZnO nanorods and on the creation of a compact transcrystallinity structure. A degradation of PLA matrix was detected but it was positively counteracted by the better interfacial stress transfer. This study offers a novel approach for modifying the fibre–matrix interface of biocomposites intended for high-performance applications. [ABSTRACT FROM AUTHOR] more...

The present research is focused on the synthesis of hexagonal ZnO wurtzite nanorods for the decoration of commercially available electrospun nylon nanofibers. The growth of ZnO was performed by a hydrothermal technique and for the first time on commercial electrospun veils. The growth step was optimized by adopting a procedure with the refresh of growing solution each hour of treatment (Method 1) and with the maintenance of a specific growth solution volume for the entire duration of the treatment (Method 2). The overall treatment time and volume of solution were also optimized by analyzing the morphology of ZnO nanostructures, the coverage degree, the thermal and mechanical stability of the obtained decorated electrospun nanofibers. In the optimal synthesis conditions (Method 2), hexagonal ZnO nanorods with a diameter and length of 53.5 nm ± 5.7 nm and 375.4 nm ± 37.8 nm, respectively, were obtained with a homogeneous and complete coverage of the veils. This easily scalable procedure did not damage the veils that could be potentially used as toughening elements in composites to prevent delamination onset and propagation. The presence of photoreactive species makes these materials ideal also as environmentally friendly photocatalysts for wastewater treatment. In this regard, photocatalytic tests were performed using methylene blue (MB) as model compound. Under UV light irradiation, the degradation of MB followed a first kinetic order data fitting and after 3 h of treatment a MB degradation of 91.0% ± 5.1% was achieved. The reusability of decorated veils was evaluated and a decrease in photocatalysis efficiency was detected after the third cycle of use. [ABSTRACT FROM AUTHOR] more...

This study deals with the development and optimization of hybrid composites integrating microcrystalline cellulose and short basalt fibers in a polypropylene (PP) matrix to maximize the mechanical properties of resulting composites. To this aim, the effects of two different coupling agents, endowed with maleic anhydride (MA-g(grafted)-PP) and acrylic acid (AA-g-PP) functionalities, on the composite properties were investigated as a function of their amount. Tensile, flexural, impact and heat deflection temperature tests highlighted the lower reactivity and effectiveness of AA-g-PP, regardless of reinforcement type. Hybrid formulations with basalt/cellulose (15/15) and with 5 wt. % of MA-g-PP displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, and notched Charpy impact strength, of 45% and 284%, 97% and 263%, and 13%, in comparison with neat PP, respectively. At the same time, the thermo-mechanical stability was enhanced by 65% compared to neat PP. The results of this study, if compared with the ones available in the literature, reveal the ability of such a combination of reinforcements to provide materials suitable for automotive applications with environmental benefits. [ABSTRACT FROM AUTHOR] more...

A thermoplastic starch (TPS) material is developed, based on corn starch plasticized with glycerol and citric acid in a 9:3:1 ratio and further bonded with isinglass and mono- and diglycerides of fatty acids (E471). In TPS, leather fragments, in the amount of 7.5 15 or 22.5 g/100 g of dry matter, were also introduced. The mixture was heated at a maximum temperature of 80 °C, then cast in an open mold to obtain films with thickness in the range 300 ± 50 microns. The leather fragments used were based on collagen obtained from production waste from shoemaking and tanned with tannins obtained from smoketree (Rhus cotinus), therefore free from chromium. Thermogravimetric (TGA) tests suggested that material degradation started at a temperature around 285 °C, revealing that the presence of leather fragments did not influence the occurrence of this process in TPS. Tensile tests indicated an increase in tensile properties (strength and Young's modulus) with increasing leather content, albeit coupled, especially at 22.5 wt%, with a more pronounced brittle behavior. Leather waste provided a sound interface with the bulk of the composite, as observed under scanning electron microscopy. The production process indicated a very limited degradation of the material after exposure to UV radiation for eight days, as demonstrated by the slight attenuation of amide I (collagen) and polysaccharide FTIR peaks. Reheating at 80 °C resulted in a weight loss not exceeding 3%. [ABSTRACT FROM AUTHOR] more...

The present work investigates the effects of an environmentally friendly treatment based on supercritical carbon dioxide (scCO2) on the interfacial adhesion of flax fibers with thermoset matrices. In particular, the influence of this green treatment on the mechanical (by single yarn tensile test), thermal (by TGA), and chemical (by FT-IR) properties of commercially available flax yarns was preliminary addressed. Results showed that scCO2 can significantly modify the biochemical composition of flax fibers, by selectively removing lignin and hemicellulose, without altering their thermal stability and, most importantly, their mechanical properties. Single yarn fragmentation test results highlighted an increased interfacial adhesion after scCO2 treatment, especially for the vinylester matrix, in terms of reduced debonding and critical fragment length values compared to the untreated yarns by 18.9% and 15.1%, respectively. The treatment was less effective for epoxy matrix, for which debonding and critical fragment length values were reduced to a lesser extent, by 3.4% and 3.7%, respectively. [ABSTRACT FROM AUTHOR] more...

The Achilles heel of thermoplastic natural fibre composites is their limited durability. The environmental degradation of the mechanical properties of hemp and hemp/basalt hybrid-reinforced high-density polyethylene (HDPE) composites has been investigated with a special focus on the effects of water ageing and accelerated ageing, including hygrothermal and UV radiation. Modification of the matrix was carried out using a maleic anhydride high-density polyethylene copolymer (MAPE) as a compatibilizer. Hybridization of hemp fibres with basalt fibres and the incorporation of MAPE were found to significantly decrease the water uptake (up to 75%) and increase the retention of mechanical properties after accelerated ageing. Secondary crystallization phenomena occurring in the composites, as confirmed by differential scanning calorimetry (DSC) analysis, were able to counteract the severe combined effects of hygrothermal stress and UV radiation, with the exception of hemp-fibre composites where permanent damage to the fibres occurred, with 2% and 20% reduction in tensile strength and modulus, respectively, for a 30 wt % hemp fibre-reinforced HDPE. [ABSTRACT FROM AUTHOR] more...

In an attempt to increase the low-velocity impact response of natural fiber composites, a new hybrid intraply woven fabric based on flax and basalt fibers has been used to manufacture laminates with both thermoplastic and thermoset matrices. The matrix type (epoxy or polypropylene (PP) with or without a maleated coupling agent) significantly affected the absorbed energy and the damage mechanisms. The absorbed energy at perforation for PP-based composites was 90% and 50% higher than that of epoxy and compatibilized PP composites, respectively. The hybrid fiber architecture counteracted the influence of low transverse strength of flax fibers on impact response, irrespective of the matrix type. In thermoplastic laminates, the matrix plasticization delayed the onset of major damage during impact and allowed a better balance of quasi-static properties, energy absorption, peak force, and perforation energy compared to epoxy-based composites. [ABSTRACT FROM AUTHOR] more...

Considering the major role played by sandwich structures in many fields where high stiffness-to-weight ratio is required, the selection of a suitable core material is of paramount importance. In order to face the environmental problems related to waste disposal, the selection of an eco-friendly core material is now included in the design criteria of sandwich structures. Agglomerated cork is recognized as a good solution that combines satisfactory mechanical performances and eco-sustainability. Many research studies individually addressed cork's morphological, thermal, and mechanical features without providing a comprehensive overview of the relationships that exist between them. In this work, the investigation of the peculiar cork morphology allowed learning more about its good insulation capacity and its impressive recovery capability. The use of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) clarified the influence of temperature on both flexural and compressive performances. The effect of testing parameters such as temperature and speed on agglomerated cork properties was validated through statistical analysis. Moreover, to highlight agglomerated cork advantages and drawbacks, the work provides also a comparison with more traditional polyvinylchloride (PVC) foams commonly used in industrial applications. more...