The influence of L-lactide content (between 15% and 43%) on the degradation of biodegradable polyurethanes (PUs) for tissue engineering was systematically addressed in this study. An ideal tissue scaffold should exhibit a mechanical response and degradability appropriate for the host tissue. To achieve it, polyols containing ε-caprolactone and L-lactide moieties were used, with the random distribution of lactide units disrupting the regularity, and hence the crystallinity, of poly(caprolactone) segments, facilitating their degradation. The biodegradable PUs were synthesised using these copolymers as soft segments and were characterised through various physicochemical techniques, including bioassays and water absorption measurements. It was determined that mechanical behaviour and water absorption depended significantly on molecular weight, L-lactide content in the soft segment, and the crystallinity of the hard segment. Additionally, two types of chain extenders were also evaluated: hydrolysable and non-hydrolysable. PUs based on hydrolysable chain extenders achieved higher molecular weights and exhibited better mechanical performance than their non-hydrolysable counterparts. To assess the cytocompatibility of these materials, an endothelial model was used, involving metabolic activity and DNA content analysis. The results demonstrated good cell adhesion and the absence of toxicity, confirming the viability of cell growth on the surfaces of these biodegradable PUs. The PUs developed in this study exhibited a low initial modulus and adjustable mechanical properties, highlighting their potential application in tissue engineering as biodegradable and biocompatible biomedical materials.

Low-field time-domain proton Nuclear Magnetic Resonance (NMR) spectroscopy is an attractive and powerful tool for studying the structure and dynamics of elastomers. The existence of crosslinks and other topological constraints in rubber matrices (entanglements and filler–rubber interactions, among others) renders the fast segmental fluctuations of the polymeric chains non-isotropic, obtaining nonzero residual dipolar couplings, which is the main observable of MQ-NMR experiments. A new software, Multiple quantum nuclear magnetic resonance analyzer for Elastomeric Networks v2 (MEW2), provides a new tool to facilitate the study of the molecular structure of elastomeric materials. This program quantitatively analyzes two different sets of experimental data obtained in the same experiment, which are dominated by multiple-quantum coherence and polymer dynamics. The proper quantification of non-coupled network defects (dangling chain ends, loops, etc.) allows the analyzer to normalize the multiple quantum intensity, obtaining a build-up curve that contains the structural information without any influence from the rubber dynamics. Finally, it provides the spatial distribution of crosslinks using a fast Tikhonov regularization process based on a statistical criterion. As a general trend, this study provides an automatic solution to a tedious procedure of analysis, demonstrating a new tool that accelerates the calculations of network structure using ¹H MQ-NMR low-field time-domain experiments for elastomeric compounds.

End-of-life tires (ELTs) are an important source of energy and materials, with ELT powder (ELTp) being a secondary raw material of increasing industrial interest. However, the complex structure and composition of ELTp rubber pose technological difficulties and scientific challenges in some high-performance applications in the rubber industry. The mechanical recycling of ELTp produces ground tire rubber (GTR) powder, which is used, among other applications in the rubber field, to prepare thermoplastic vulcanizates (TPVs) due to the interest in these materials in the automotive and construction sectors. Over the last few decades, different approaches have been explored to minimize the limitations of these TPVs, including their large particle size and poor compatibility with GTR powder in other polymer matrices. This study applies different recycling procedures to GTR powder, based on thermal, chemical and mechanical methods, and combinations thereof, to minimize interfacial issues with other matrices used in TPV preparation. The effect of the different rubber recycling processes on the performance of the resulting TPVs was evaluated, optimizing the fraction of recycled rubber from ELTp and the vulcanization system to enhance the mechanical properties and obtain industrially competitive products.

End-of-life tyres (ELT) are an important source of energy and materials, with ELT powder (ELTp) being a secondary raw material of increasing industrial interest. However, the complex structure and composition of ELTp rubber pose technological difficulties and scientific challenges in some high-performance applications in the rubber industry. The mechanical recycling of ELTp produces ground tyre rubber (GTR) powder, which is used, among other applications in the rubber field, to prepare thermoplastic vulcanizates (TPV) due to the interest in these materials in the automotive and construction sectors. Over the last decades, different approaches have been explored to minimize the limitations of these TPVs relating to the large particle size and poor compatibility of GTR powder with other polymer matrices. This study applies different recycling procedures to GTR powder, based on thermal, chemical and mechanical methods, and combinations thereof, to minimize interfacial issues with other matrices used in TPV preparation. The effect of the different rubber recycling processes on the performance of the resulting TPVs was evaluated, optimizing the fraction of recycled rubber from ELTp and the vulcanization system to enhance the mechanical properties and obtain industrially competitive products.