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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 [...]

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 [...]

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]

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 [...]

This study investigated the self-healing properties of PA6/COC blends, in particular, the impact of three compatibilizers on the rheological, microstructural, and thermomechanical properties. Dynamic rheological analysis revealed that ethylene glycidyl methacrylate (E-GMA) played a crucial role in reducing interfacial tension and promoting PA6 chain entanglement with COC domains. Mechanical tests showed that poly(ethylene)-graft-maleic anhydride (PE-g-MAH) and polyolefin elastomer-graft-maleic anhydride (POE-g-MAH) compatibilizers enhanced elongation at break, while E-GMA had a milder effect. A thermal healing process at 140 °C for 1 h was carried out on specimens broken in fracture toughness tests, performed under quasi-static and impact conditions, and healing efficiency (HE) was evaluated as the ratio of critical stress intensity factors of healed and virgin samples. All the compatibilizers increased HE, especially E-GMA, achieving 28.5% and 68% in quasi-static and impact conditions, respectively. SEM images of specimens tested in quasi-static conditions showed that all the compatibilizers induced PA6 plasticization and crack corrugation, thus hindering COC flow in the crack zone. Conversely, under impact conditions, E-GMA led to the formation of brittle fractures with planar surfaces, promoting COC flow and thus higher HE values. This study demonstrated that compatibilizers, loading mode, and fracture surface morphologies strongly influenced self-healing performance. [ABSTRACT FROM AUTHOR]

In the contemporary emphasis on weight reduction, the utilization of advanced materials like Carbon Fiber Reinforced Polymers (CFRPs) and cutting-edge technologies such as 3D printing of metal is increasingly crucial. This study delves into the junction of CFRP and titanium, aiming to conduct Single Lap shear tests on specimens featuring a co-lamination of long fiber composite onto a metal lattice structure. Different specimens with different dimensions of the Simple Cubic (SC) unit cell were subjected to testing. A microscope investigation facilitated an exploration of junction failure and epoxy resin infiltration into the lattice substrate. Employing an efficient 2D Finite Element Model, the homogenization process yielded theoretical models underestimating the Young Modulus by approximately 10% compared to real specimens. Despite the challenges in bonding titanium and CFRP, the novel junction exhibited a shear stress of 17.25 MPa, which is nearly equivalent to those of a co-lamination between sandblasted steel and CFRP, that is 17.15 MPa. [ABSTRACT FROM AUTHOR]

Aim of this work is to develop a novel epoxy based nanocomposite and to analyse its shape memory behavior. In particular, silver nanoparticles are in-situ generated within an epoxy resin subsequently filled with both carbon black (CB) and carbon nanofibers (NFs) at different ratios and at a total amount of 4 wt%. Differential scanning calorimetry shows how the introduction of both CB and NF induces a slight decrease of the glass transition temperature ([T.sub.g]) of the samples. The [T.sub.g] drop due to nanofiller addition determines a decrease of both flexural modulus and stress at yield with respect to the neat resin, especially at elevated CB concentrations, while the presence of Ag nanoparticles plays a positive effect on the flexural properties. The best mechanical properties can be detected at a CF/NF ratio of 50%, coupled with a noticeable decrease of the electrical resistivity down to [10.sup.2] [ohm] x cm and an interesting heating capability through Joule effect. The electro-mechanical shape-memory characterization under bending configuration demonstrates how it is possible to obtain an almost complete shape recovery after 60 s under an applied voltage of 220 V., INTRODUCTION Epoxy resins are nowadays the most widely applied matrices for structural composites, because of their limited density and their good adhesive and mechanical performances. Thanks to their chemical versatility [...]