Polyurethanes have gained prominence across various industrial sectors due to their versatility, flexibility, and durability. They are widely used in applications such as construction, packaging, textiles, and footwear. Traditionally, their production relies on fossil-derived raw materials, but increasing efforts are being made to enhance their sustainability. Among the most promising approaches are waterborne polyurethane dispersions (PUDs), where the polymer is modified to disperse in water, a more environmentally friendly medium. Another strategy involves the use of renewable, biobased polyols. The aim of this study was to develop more sustainable PUDs for use as adhesives in the footwear industry by increasing the biobased content of the formulations. Five biobased polyols were tested, alongside a dispersion made with a biodegradable synthetic polyol (used as a laboratory-scale reference) and a commercial dispersion (used as an industrial benchmark). The synthesis was carried out in a batch reactor, involving steps for pre-polymer preparation, neutralisation, phase inversion, and chain extension under controlled heating, mechanical stirring, and an inert atmosphere. The resulting dispersions had a biobased content exceeding 50%, with the PRI3238-based sample reaching 69.45%. The formulations demonstrated pH values ranging from 6.71 to 7.72, viscosity between 4.8 and 15 mPa·s, and solid content above 30%, meeting literature requirements. Zeta potentials above -30 mV indicated adequate stability. The derived films displayed variations in opacity, while FTIR analysis confirmed the presence of urea and urethane groups, indicating successful chemical reactions. Thermal testing showed that materials incorporating biobased polyols exhibited greater thermal resistance (mass losses between 255 °C and 450 °C) compared to synthetic ones. In adhesion tests, only the PRI3294 and PCL2000 samples exceeded the 5 N/mm threshold required by the technical specification across all three proposed scenarios.
