Impact of recycled polyol content on the structure and performance of reactive polyurethane hot-melt adhesive

The adhesive industry is undergoing a transformation towards circularity, seeking sustainable alternatives to fossil-based raw materials. Although bio-based feedstocks have attracted interest, their high cost and limited availability often constrain industrial implementation. As a viable alternative, recycled raw materials derived from polymer waste are being explored to reduce environmental impact while maintaining performance. In this study, a chemically recycled polyol was obtained through glycolysis of post-industrial rigid polyurethane foam waste and used to prepare a hot-melt reactive polyurethane adhesive formulation. The recycled polyol was characterized to evaluate the transfer of additives and residual compounds from the original waste into the adhesive. Particular attention was given to the presence of plasticizers and aromatic amines and their migration into the adhesive due to the antiadherent behavior of the former and the potential toxicity of the latter. The influence of increasing recycled polyol content on adhesive properties was analyzed by FTIR, DSC, TGA, rheology and peel strength of leather/adhesive/SBR joints. Results revealed that glycolysis generated aromatic amines and transferred plasticizers from waste to the adhesive. Nevertheless, the adhesives exhibited good processability and excellent peel strength before and after thermal aging, demonstrating that chemically recycled polyols can serve as high-performance components for adhesive systems.