This paper briefly discusses the utilization of pruning wastes as a lignocellulosic source of cellulose fibers, which could be of potential use in the development of valuable materials such as sustainable textiles and fillers for footwear components including uppers and soles. Phoenix canariensis palm leaves, one of the most common plants found in the local environment of the Alicante region (Spain), was used as a biomass raw material. Determining appropriate processing parameters and their desired range of maximum cellulose extraction states is key to improving yields. Therefore, this study aimed at determining the effect of processing conditions on cellulose extraction by optimizing the hydrothermal process, as a part of overall combined processes involving several steps. Specifically, the time of the steam-explosion stage was varied between 15 and 33 min in order to maximize the cellulose extraction yield. The composition of both the extracted fibers and the resulting by-product solutions generated during the different steps were determined by FTIR and TGA in order to analyze the effectiveness of removing hemicellulose, lignin and extractives as well as the removed substances at each stage for their further valorization. Additionally, the morphology of cellulosic fibers was evaluated by SEM and their crystallinity by XRD. Crystalline cellulose fibers were successfully extracted from pruning biomass wastes, achieving more efficient removal of hemicellulose and lignin when the hydrothermal process was assessed over 25–33 min. This resulted in finer and smoother fibers, but the crystallinity of α-cellulose decreased as the time of steam-explosion increased to 33 min. The characterization of waste solutions generated after the different extraction steps confirmed that the most effective treatments to remove lignin and hemicellulose from the cell wall are alkaline pretreatment and a hydrothermal process.

The aim of this work is to develop sustainable reactive polyurethane hot melt adhesives (HMPUR) for footwear applications based on biobased polyols as renewable resources, where ma-croglycol mixtures of polyadipate of 1,4-butanediol, polypropylene and different biobased polyols were employed and further reacted with 4-4′-diphenylmethane diisocyanate. The different reactive polyurethane hot melt adhesives obtained were characterized with different experimental techniques, such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), softening temperature and melting viscosity. Finally, their adhesion properties were measured from T-peel tests on leather/HMPUR adhesives/SBR rubber joints in order to establish the viability of the used biobased polyols and the amount of these polyols that could be added to reactive polyurethane hot melt adhesives satisfactorily to meet the quality requirements of footwear joints. All biobased polyols and percentages added to the polyurethane adhesive formulations successfully met the quality requirements of footwear, being comparable to traditional adhesives currently used in footwear joints in terms of final strength. Therefore, these new sustainable polyurethane adhesives can be considered as suitable and sustainable alternatives to the adhesives commonly used in footwear joints.

The aim of this work is to develop hydrophobic coatings on leather materials by plasma polymerisation with a low-pressure plasma system using an organosilicon compound, such as hexamethyldisiloxane (HMDSO), as chemical precursor. The hydrophobic coatings obtained by this plasma process were evaluated with different experimental techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and standardised tests including colour measurements of the samples, surface coating thickness and water contact angle (WCA) measurements. The results obtained indicated that the monomer had polymerised correctly and completely on the leather surface creating an ultra-thin layer based on polysiloxane. The surface modification produced a water repellent effect on the leather that does not alter the visual appearance and haptic properties. Therefore, the application of the plasma deposition process showed promising results that makes it a more sustainable alternative to conventional functional coatings, thus helping to reduce the use of hazardous chemicals in the finishing process of footwear manufacturing.

This work proposes the use of silver nanoparticles (AgNPs) to inhibit the bacterial growth of waterborne polyurethane adhesives. Therefore, AgNPs were synthesized from AgNO₃ using a natural polymer like gelatine as a reducing and stabilizing agent. The AgNPs exhibited a strong antimicrobial activity at very low concentrations. The incorporation of gelatine-stabilized AgNPs conferred antimicrobial properties on waterborne polyurethane adhesives without significantly altering their chemical, thermal, and adhesive properties.

In this work, the use of silver-based silica nanocomposites (Ag@SiO₂) was proposed to inhibit the microorganism growth of waterborne polyurethane adhesives. For that purpose, colloidal silver nanoparticles were prepared and embedded in a SiO₂-based matrix in order to decrease the silver aggregation tendency. The protection of AgNPs with silica was also intended to improve the stability of the adhesive toward metallic particles. Last but not least, Ag@SiO₂ provides safer handling of the silver nanoparticles due to their immobilisation within the silica matrix. Colloidal silver was prepared by the Creigthon method using NaBH₄ as a reducing agent and polyvinylpyrrolidone (PVP) as a stabilising agent. The coating of the AgNPs by the silica matrix was achieved through a modified Stöber process. The stability of the AgNPs in different amino-based catalysts for the silica matrix synthesis was evaluated in order to successfully obtain silver–silica core-shell nanocomposites. After that, AgNPs and Ag@SiO₂ nanocomposites were incorporated in a waterborne polyurethane adhesive and the chemical, thermal adhesion and antimicrobial properties were evaluated.