Polyurethane Recycling Through Acidolysis: Current Status and Prospects for the Future

Abstract

Polyurethane (PU) stands out as a crucial category of polymers which have become indispensable in improving our quality of life, revolutionizing various aspects of human existence. However, this convenience comes with a dark side – the environmental impact associated with its disposal. Nevertheless, recycling presents a promising solution, aligning with the principles of a circular economy by transforming polymer waste into new materials. A notable focus within this realm is the utilization of dicarboxylic acids (DA) as depolymerization agents, achieved through a process known as acidolysis. This method has proven to be an exceptional solution, primarily explored for recycling PU foams and subsequently employed in the production of new foams. The resulting recycled polyol finds successful applications in various PU products, including rigid and flexible foams, adhesives, and coatings. Analyzing the impact of recycled polyol on the properties of new PU products reveals interesting insights. While it slightly affects the morphology and color of foams, there is no significant impact on density or thermal conductivity. Notably, flexible foams exhibit increased stiffness when produced using recycled polyol. Additionally, the strength of PU adhesives and the surface hardness of PU coatings are enhanced with the incorporation of recycled polyol, albeit with a reduction in gloss. The recycled PU coatings also display a more hydrophobic surface. Considering both environmental and economic benefits, the advantages of this approach are evident. With the aim of catering to the needs of both the academic and industrial sectors, this review delves into the subject of PU recycling via acidolysis, subsequently exploring the utilization of recycled materials in the creation of new PU products. The review offers an in-depth explanation of the acidolysis process and thoroughly examines the degradation mechanisms involved. Additionally, it scrutinizes the impact of reaction conditions on the properties of the recycled materials and investigates their applicability in the production of novel materials. Moreover, the review presents an analysis of the environmental and economic implications associated with these processes. In summary, this review overviews the current status of acidolysis of PU and prospects for its future.