This paper focuses on the optimisation of an efficient extraction process for cellulose and lignin from rice straw waste from the Albufera of Valencia using the steam explosion method. This method is particularly pertinent given the environmental and economic challenges posed by the current disposal practices of agricultural waste. The technique comprises a high-temperature cooking stage followed by instantaneous decompression, effectively altering the biomass’s physical and chemical properties to enhance its surface area and porosity. Our adaptation of the steam explosion technique specifically addresses the challenges of rice straw waste, marking a significant departure from previous applications. This innovation is crucial in addressing the urgent need for more sustainable waste management practices, as it effectively deconstructs the lignocellulosic matrix of rice straw. This facilitates the selective extraction of cellulose at a 70% efficiency, with a 20% yield and the subsequent recovery of lignin. The results of this study are significant for sustainable biomaterial production, offering novel insights into optimising these crucial biomass components. By refining the process and focusing on critical parameters, our work advances the application of steam explosion methods for agricultural waste, enhancing efficiency and sustainability. By utilising rice straw biowaste, this research not only proposes a solution to a pressing environmental issue but also demonstrates the potential to create new market opportunities, increase the economic value for rice producers, and significantly reduce the environmental footprint of existing waste disposal methods. The holistic and ecological approach of this study underscores the vital need for innovative strategies in agricultural waste management, positioning the valorisation of rice straw waste as a key component in the pursuit of environmental sustainability.

The quest for sustainable and efficient methods for extracting cellulose nanocrystals (CNCs) remains critical in the development of advanced materials. This study refines the acid hydrolysis process for cellulose derived from rice straw, an abundant agricultural waste, focusing on the relationship between hydrolysis parameters and CNC properties. The research identifies conditions that enhance crystallinity and colloidal stability while effectively transforming amorphous cellulose into nanocrystals. Advanced characterization techniques, including XRD, SEM, TEM, and zeta potential measurements, provided insights into the structural and colloidal properties of CNCs. The findings demonstrate the influence of reaction temperature, time, and acid concentration on CNC quality, with optimized conditions yielding nanocrystals with enhanced stability and well-defined morphology. This study underscores the potential of rice straw as a renewable resource, advancing the circular economy by promoting the use of sustainable materials in high-value applications such as composite reinforcement and coatings.

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.

In response to the environmental impacts of conventional polyurethane adhesives derived from fossil fuels, this study introduces a sustainable alternative utilizing lignin-based polyols extracted from rice straw through a process developed at INESCOP. This research explores the partial substitution of traditional polyols with lignin-based equivalents in the synthesis of reactive hot melt polyurethane adhesives (HMPUR) for the footwear industry. The performance of these eco-friendly adhesives was rigorously assessed through Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), rheological analysis, and T-peel tests to ensure their compliance with relevant industry standards. Preliminary results demonstrate that lignin-based polyols can effectively replace a significant portion of fossil-derived polyols, maintaining essential adhesive properties and marking a significant step towards more sustainable adhesive solutions. This study not only highlights the potential of lignin in the realm of sustainable adhesive production but also emphasises the valorisation of agricultural by-products, thus aligning with the principles of green chemistry and sustainability objectives in the polymer industry.

Covalent adaptable networks (CANs) represent a pioneering advance in polymer science, offering unprecedented versatility in materials design. Unlike conventional adhesives with irreversible bonds, CAN-based polyurethane adhesives have the unique ability to undergo chemical restructuring through reversible bonds. One of the strategies for incorporating these types of reactions in polyurethanes is by functionalisation with Diels–Alder (DA) adducts. By taking advantage of the reversible nature of the DA chemistry, the adhesive undergoes controlled crosslinking and decrosslinking processes, allowing for precise modulation of bond strength. This adaptability is critical in applications requiring reworkability or recyclability, as it allows for easy disassembly and reassembly of bonded components without compromising the integrity of the material. This study focuses on the sustainable synthesis and characterisation of a solvent-based polyurethane adhesive, obtained by functionalising a polyurethane prepolymer with DA diene and dienophiles. The characterisation of the adhesives was carried out using different experimental techniques: nuclear magnetic resonance spectroscopy (NMR), Brookfield viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and T-peel strength testing of leather/adhesive/rubber joints to determine the adhesive properties, both before and after the application of external stimuli. The conversion of both the DA and retro-Diels–Alder (r-DA) reactions was confirmed by ¹H-NMR. The adhesive properties were not altered by the functionalisation of the adhesive prepolymer, showing similar thermal resistance and good rheological and adhesive properties, even exceeding the most demanding technical requirements for upper-to-sole joints in footwear. After the application of an external thermal stimuli, the bonded materials separated without difficulty and without damage, thus facilitating their separation, recovery and recycling.

The increasing concern for sustainability in the footwear industry has spurred the exploration of eco-friendly alternatives for materials commonly used in sole manufacturing. This study examined the effect of incorporating rice straw and cellulose as fillers into soles made from either styrene–butadiene rubber (SBR) or thermoplastic polyurethane (TPU). Both fillers were used as a substitute in mass percentages ranging from 5 to 20% in the original SBR and TPU formulas, and their impact on mechanical properties such as abrasion and tear resistance, as well as thermal properties, was thoroughly evaluated. The results demonstrated that the inclusion of fillers affects the overall performance of the soles, with the optimal balance of mechanical and thermal properties observed at a 10% filler content. At this level, improvements in durability were achieved without significantly compromising flexibility or abrasion resistance. Thermal analysis revealed increased thermal stability at moderate filler contents. This research not only offers a sustainable alternative to traditional materials but also enhances sole performance by improving the composition. Furthermore, this study paves the way for future research on the feasibility of incorporating eco-friendly materials into other consumer product applications, highlighting a commitment to innovation and sustainability in product design.