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The cure kinetics of various epoxy resin mixtures, comprising a bisphenol epoxy, two epoxy modifiers, and two hardening agents derived from cardanol technology, were investigated through differential scanning calorimetry (DSC). The development of these mixtures aimed to achieve epoxy materials with a substantial bio-content up to 50% for potential automotive applications, aligning with the 2019 European Regulation on climate neutrality and CO2 emission. The Friedman isoconversional method was employed to determine key kinetic parameters, such as activation energy and pre-exponential factor, providing insights into the cross-linking process and the Kamal–Sourour model was used to describe and predict the kinetics of the chemical reactions. This empirical approach was implemented to forecast the curing process for the specific oven curing cycle utilised. Additionally, tensile tests revealed promising results showcasing materials' viability against conventional counterparts. Overall, this investigation offers a comprehensive understanding of the cure kinetics, mechanical behaviour, and thermal properties of the novel epoxy–novolac blends, contributing to the development of high-performance materials for sustainable automotive applications. [ABSTRACT FROM AUTHOR]

The patterning of composites with carbon-based additives of nanometer or micrometer size was studied by the precise modification of material surfaces using laser technology. Initially, the composites are electrical insulators, but we can make them conductive by selective patterning; this process allows us to create conductive tracks within seconds, with a sheet resistance that can be adjusted over a wide range, from 108 Ω/sq down to 2.5 Ω/sq. The additives used include graphene nanoplatelets, graphene oxide nanosheets, and aramid fibers. By conducting microscopic and spectroscopic characterizations before and after laser treatment, we can distinguish between two different processes that lead to electrical conduction: (a) localized increase in the concentration of conductive additives or (b) localized reduction and pyrolysis of insulating additives. To demonstrate the versatility and usefulness of this technique in different fields of application, such as automotive, we fabricate three different devices on polyurethane: a heater, a proximity sensor, and an amperometric sensor for detecting biological analytes. [ABSTRACT FROM AUTHOR]

Melatonin (MT) is a vital hormone controlling biorhythms, and optimizing its release in the human body is crucial. To address MT's unfavorable pharmacokinetics, we explored the inclusion complexes of MT with β-cyclodextrin (β-CD). Nano spray drying was applied to efficiently synthesize these complexes in three molar ratios (MT : β-CD = 1 : 1, 2 : 1, and 1 : 2), reducing reagent use and expediting inclusion. The complex powders were characterized through thermal analyses (TGA and DSC), Fourier transform infrared spectroscopy (FTIR), and in vitro MT release measurements via high-performance liquid chromatography (HPLC). In parallel, computational studies were conducted, examining the stability of MT : β-CD complexes by means of unbiased semi-empirical conformational searches refined by DFT, which produced a distribution of MT : β-CD binding enthalpies. Computational findings highlighted that these complexes are stabilized by specific hydrogen bonds and non-specific dispersive forces, with stronger binding in the 1 : 1 complex, which was corroborated by in vitro release data. Furthermore, the alignment between simulated and experimental FTIR spectra demonstrated the quality of both the structural model and computational methodology, which was crucial to enhance our comprehension of optimizing MT's release for therapeutic applications. [ABSTRACT FROM AUTHOR]

Nanocomposite materials have recently attracted great attention for their wide range of applications, such as in smart materials, flexible electronics, and deformation sensing applications. Such materials make it possible to combine a polymer with functional fillers. In this study, flexible artificial leathers, exhibiting insulating properties and containing 1.5 or 2wt.% of graphene oxide (GO) in the polyurethane (PU) layer, were electrically activated via CO2 laser irradiation to obtain conductive paths at the surface exposed to the laser beam. As the material retained its insulating properties out of the irradiation areas, the laser scribing method allowed, at least in principle, a printed circuit to be easily and quickly fabricated. Combining a variety of investigation methods, including scanning electron microscopy (SEM), optical profilometry, IR and Raman spectroscopies, and direct current (DC) and alternate current (AC) electrical measurements, the effects of the laser irradiation were investigated, and the so-obtained electrical properties of laser-activated GO/PU regions were elucidated to unveil their potential use in both static and dynamic mechanical conditions. In more detail, it was shown that under appropriate CO2 laser irradiation, GO sheets into the GO/PU layer were locally photoreduced to form reduced-GO (RGO) sheets. It was verified that the RGO sheets were entangled, forming an accumulation path on the surface directly exposed to the laser beam. As the laser process was performed along regular paths, these RGO sheets formed electrically conductive wires, which exhibited piezoresistive properties when exposed to mechanical deformations. It was also verified that such piezoresistive paths showed good reproducibility when subjected to small flexural stresses during cyclic testing conditions. In brief, laser-activated GO/PU artificial leathers may represent a new generation of metal-free materials for electrical transport applications of low-current signals and embedded deformation sensors. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate is a thermoplastic polymer with a wide range of uses, including synthetic fibres and containers for beverages and other liquids. Recycling plastics reduces the amount of energy and natural resources needed to create virgin plastics. Polyethylene terephthalate containers and bottles are collected and then broken down into small flakes used to produce new products such as textile fibres. Thermo-mechanical degradation may happen during the recycling process and presence of contaminants affects the final product characteristics. Two kinds of recycled polyethylene terephthalate fibres were used for fabrics production: post-consumer polyethylene terephthalate fibres and a blend of post-consumer and post-industrial polyethylene terephthalate fibres. Focusing on knitted and flat-woven textile structures, main mechanical properties of the fabrics were assessed by various tests, like tensile strength test and wear resistance test. A comparative study with the current production of virgin polyethylene terephthalate fabrics was useful to evaluate high standards accordance for automotive field. Both knitted and flat-woven recycled polyethylene terephthalate fabrics had excellent performance after mechanical tests. Post-consumer polyethylene terephthalate fabrics had the best results, especially after wear resistance test. These results allow an evaluation of their applications. [ABSTRACT FROM AUTHOR]