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This study presents the formulation and comprehensive characterization of compatibilized polyamide 6 (PA6)/cyclic olefin copolymer (COC) blends with the aim of developing a self-healing matrix for thermoplastic structural composites. Rheological analysis highlighted the compatibilizing effect of ethylene glycidyl methacrylate (E-GMA), as evidenced by an increase in viscosity, melt strength (MS), and breaking stretching ratio (BSR), thus improving the processability during film extrusion. E-GMA also decreased COC domain size and improved the interfacial interaction with PA6, which was at the basis of a higher tensile strength and strain at break compared to neat PA6/COC blends. E-GMA also significantly boosted the healing efficiency (HE), measured via fracture toughness tests in quasi-static and impact conditions. The optimal healing temperature was identified as 160 °C, associated with an HE of 38% in quasi-static mode and 82% in impact mode for the PA6/COC blends with an E-GMA content of 5 wt% (PA6COC_5E-GMA). The higher healing efficiency under impact conditions was attributed to the planar fracture surface, which facilitated the flow of the healing agent in the crack zone, as proven by fractography analysis. This work demonstrates the potential of E-GMA in fine-tuning the thermomechanical properties of PA6/COC blends. PA6COC_5E-GMA emerged as the formulation with the best balance between processability and self-healing efficiency, paving the way for advanced multifunctional self-healing thermoplastic composites for structural applications. [ABSTRACT FROM AUTHOR]

Materials able to store thermal energy can be a useful strategy to reduce energy consumption of buildings and to decrease greenhouse gases emissions. In this work, for the first time, the technique of salt leaching has been used to produce novel polyethylene foams containing different amounts of a microencapsulated phase-change material (PCM) with a melting point of 24[degrees]C, to be potentially applied in building insulation. The microstructural, thermal, and mechanical properties of produced foams have been comprehensively investigated. The prepared foams were characterized by high values of open porosity (about 60%) and by density values around 0.4 g/[cm.sup.3]. Infrared thermography analysis demonstrated that the time required from the samples to reach a set temperature, thanks to the presence of PCM, was up to two times higher with respect to the reference foam. Therefore, these materials could store/release an interesting amount of thermal energy. Shore-A measurements evidenced that the addition of PCM generally led to a softening of the foams. Tensile mechanical tests confirmed the softening effect provided by the addition of the microcapsules, with a decrease of the stiffness and of the strength of the material. Interestingly, strain-at-break values were considerably increased upon PCM introduction. KEYWORDS foams, phase-change materials, polyethylene, salt leaching, thermal energy storage, 1 | INTRODUCTION Recently, the improved living conditions of people and the increase of growth rate of population have led to an enhancement of the energy demands for buildings. Recent [...]

In light of the significant impact of climate change, it is imperative to identify effective solutions to reduce the environmental burdens of industrial production and to promote recycling strategies also for thermosetting polymers. In this work, the mechanical recycling of phenolic resins, obtained from industrial production scrap of plastic knobs for household appliances, was optimized. The feasibility of a partial substitution of virgin materials with recycled ones was investigated both at a laboratory and industrial scale. Finally, the environmental benefits arising from the use of recycled material were quantified through a life cycle assessment (LCA). The results of laboratory characterization demonstrated that the thermal properties of the phenolic resins were not influenced by the presence of recycled material, and the mechanical performances were not significantly impaired up to a recycled content of 30 wt%. The industrial production trials demonstrated the feasibility of replacing up to 15 wt% of virgin material without any influence on the aesthetical features of the produced components. Finally, LCA of industrially produced knobs highlighted a limited benefit of virgin material substitution in the case of novolac chromium-plated samples, while an overall environmental impact reduction of around 7–10% was detected in the case of resol-based materials. [ABSTRACT FROM AUTHOR]

Elastocaloric cooling is recognized as a promising alternative to modern vapor-compression cooling systems, which often rely on environmentally hazardous refrigerants. Natural rubber (NR), a well-known renewable resource, stands out among elastomers exhibiting elastocaloric behavior due to a peculiar combination of nontoxicity, low cost, softness, long-life fatigue and high caloric power. Despite these properties, research on the refrigeration potential of NR is still in its early stages, and several aspects require attention. This work investigates, for the first time, the effect of crosslinking density on the elastocaloric properties of NR. Samples with three different crosslinking densities (2.9, 4.0 and 5.2 mol·10−4/cm3) were produced by internal compounding and hot pressing, and thermo-mechanically characterized. The assessment of the elastocaloric effect of the produced samples revealed that reducing the crosslinking degree significantly enhanced the elastocaloric properties. To compare the cooling capacity of the samples, a qualitative coefficient of performance (COPmat) was evaluated as the ratio between extracted thermal energy and deformational work per unit volume. The results highlight that the least crosslinked sample achieved the higher COPmat, equal to 2.4. These results underscore the significance of crosslinking density as one of the primary factors to be considered to enhance the refrigeration potential of NR. [ABSTRACT FROM AUTHOR]

Featured Application: This work on 3D-printed TPU/MWCNT/PCM composites offers information on materials with significant potential for applications in advanced thermal management systems. These materials can be employed in smart textiles, wearable electronics, or flexible sensors, where precise control over temperature regulation and thermal conductivity is essential. These composites' enhanced electrical conductivity and tunable thermal properties make them promising candidates for multifunctional devices that require efficient heat dissipation, strain sensing, or even self-regulating thermal insulation. In this work, multiwalled carbon nanotubes (MWCNTs) were melt-compounded into a novel thermal energy storage system consisting of a microencapsulated paraffin, with a melting temperature of 6 °C (M6D), dispersed within a flexible thermoplastic polyurethane (TPU) matrix. The resulting materials were then processed via Fused Filament Fabrication (FFF), and their thermo-mechanical properties were comprehensively evaluated. After an optimization of the processing parameters, good adhesion between the polymeric layers was obtained. Field-Emission Scanning Electron Microscopy (FESEM) images of the 3D-printed samples highlighted a uniform distribution of the microcapsules within the polymer matrix, without an evident MWCNT agglomeration. The thermal energy storage/release capability provided by the paraffin microcapsules, evaluated through Differential Scanning Calorimetry (DSC), was slightly lowered by the FFF process but remained at an acceptable level (i.e., >80% with respect to the neat M6D capsules). The novelty of this work lies in the successful integration of MWCNTs and PCMs into a TPU matrix, followed by 3D printing via FFF technology. This approach combines the high thermal conductivity of MWCNTs with the thermal energy storage capabilities of PCMs, creating a multifunctional nanocomposite material with unique thermal management properties. [ABSTRACT FROM AUTHOR]

Various amounts of both devulcanized (DR) and non-devulcanized (NDR) recycled rubber were melt compounded with a virgin ethylene-propylene diene monomer (EPDM) rubber. The resulting compounds were then expanded by using azodicarbonamide. The role played by the presence of DR or NDR on the thermomechanical properties of the obtained materials was evaluated. Electron scanning microscope micrographs highlighted that DR particles were better encapsulated within the EPDM matrix with respect to the corresponding NDR ones. Moreover, a better interfacial adhesion was observed with DR, probably due the re-vulcanization process in which the free crosslinking sites that typically characterize DR could form linkages with the EPDM matrix. Tensile impact behavior of expanded EPDM/recycled rubber blends highlighted a strong improvement of the normalized total absorbed energy, of the normalized impact strength and of the elongation at break with respect to the neat expanded EPDM for all the investigated compositions, and especially with a DR content of 20 wt %. The preparation of expanded EPDM containing considerable amounts of devulcanized rubber was, therefore, demonstrated to be a practical route to reduce the costs and improve the properties and the environmental sustainability of rubber products. KEYWORDS elastomers, foams, recycling, rubber, 1 | INTRODUCTION It is well known that in tires production the different constituents are vulcanized together in order to form a crosslinked structure with elevated mechanical properties and dimensional [...]

The thermomechanical behavior of ethylene propylene diene monomer (EPDM) foams produced with the salt leaching method has been investigated and compared with the behavior of EPDM foams obtained from conventional blowing agents. Moreover, the salt-leaching process has been optimized to minimize salt residues and the influence of different parameters (such as average particle size and particle size distribution) has been investigated. Scanning electron microscopy and density measurements highlighted that salt-leaching leads to the formation of open-cell porosity with cell dimensions of around 60 to 80 [micro]m, while foams obtained with the two traditional foaming agents lead to closed-cell porosity. Compression set values indicate that the behavior of the foams produced with salt leaching are more similar to the unfoamed rubber, characterized by higher elasticity and low residual deformation. Two theoretical models were successfully applied to the compression curves (Mooney-Rivlin and Exponential-Logarithmic) and they highlighted the effect of foaming on the properties of EPDM rubber and in particular the higher chain extensibility obtained through the salt leaching foaming method. KEYWORDS blowing agents, density, foams, mechanical properties, model, processing, rubber, 1 | INTRODUCTION In the last few years, polymer foams have gained great interest due to their unique features. Due to the combination of low density and low thermal conductivity, [...]

Microencapsulated phase change materials (PCMs) are being increasingly employed as functional fillers in polymer matrices for thermal management. Therefore, the effect of PCM microcapsules on the rheological, microstructural, thermal and mechanical properties of the host polymer matrices must be understood. This work concerned the preparation of epoxy polymers filled with PCM microcapsules (MC) in various concentrations and their subsequent characterization. The MC phase increases the viscosity of epoxy before curing, thereby reducing castability and hindering elimination of air bubbles. The latter was reflected in an increase in porosity for highly filled compositions, as elucidated by density measurements and microscopic investigation. SEM micrographs showed that the adhesion between the capsule shell and the epoxy matrix was not optimal. The interfacial weakness and the intrinsic low Stiffiiess and strength of MC caused a reduction in mechanical properties, as evidenced by the Nicolais-Narkis and Pukanszky models. On the other hand, at zero or low deformation levels, the interface presents no gaps and is able to transfer load and heat, as demonstrated by the data of elastic modulus, modeled with the Halpin-Tsai and Lewis-Nielsen models, and those of thermal conductivity, in excellent agreement with the Pal model. KEYWORDS interfaces, mechanical properties, microencapsulation, thermal properties, thermosets, 1 | INTRODUCTION Organic phase change materials (PCMs) are the most commonly employed materials for thermal energy storage (TES), particularly at 0 to 100[degrees]C. [1] PCMs represent an innovative, renewable [...]

In fiber reinforced composite materials, the interfacial strength between the fibers and the matrix plays a key role in controlling the stress transfer and damage mechanisms of the composite. In this study, CO2 laser surface treatment of the fibers was investigated as a potential sustainable substitute for conventional chemical treatments, that can be costly and have negative environmental effects. The influence of the laser treatment on basalt fiber fabric was comprehensively investigated. The fibers were subjected to different laser power levels and characterized from a morphological and mechanical point of view. From optical and scanning electron microscopy, it was observed that the treated fibers manifested increased surface roughness along with spots of fused and bonded fibers. Individual treated fibers exhibited improved tensile properties with increased values of scale parameter (by about 21%) in the case of a laser power equal to 1.04 W/mm2, and no substantial changes in Young's modulus. The treated fibers were subsequently used in the preparation of epoxy‐based microcomposites, and microdebonding tests revealed an increase in the interfacial shear strength (IFSS) up to 8%. Therefore, this work proved that a laser surface treatment of basalt fibers is a valid alternative to conventional fiber surface modification to enhance the mechanical compatibility between fibers and matrix, and therefore to improve the mechanical performances of basalt fiber composites. Highlights: Failure in composites due to weak interfacial adhesion with epoxy.CO2 laser treatment of basalt fibers to enhance interfacial adhesion.Treated fibers exhibit improved tensile properties.Treated fibers manifested improved interfacial shear strength (IFSS, +8%). [ABSTRACT FROM AUTHOR]