Advances in Chemical Recycling of Polyurethane Waste: A Green Chemistry Perspective

Abstract: Polyurethane (PU) materials are extensively employed in construction, automotive, footwear, and packaging industries due to their durability and versatile properties. However, their crosslinked thermoset structure presents significant challenges for end-of-life disposal, contributing to persistent environmental accumulation and long-term waste management issues. In recent years, chemical recycling methods,particularly glycolysis, have gained attention as promising approaches for PU waste valorization.

Glycolysis involves the cleavage of urethane linkages using a glycol (e.g., ethylene glycol) in the presence of catalysts such as organometallic compounds. This process leads to the formation of low-molecular-weight polyols, which can be reused in repolymerization or formulation of new materials. Optimization of parameters, such as temperature, catalyst concentration, and glycol-to-PU ratio, significantly influences degradation efficiency and product quality.

Analytical techniques like FTIR, NMR, and GPC are commonly used to characterize the glycolyzed products. FTIR spectra typically show the disappearance of urethane peaks and emergence of hydroxyl functionalities, indicating successful depolymerization. NMR provides detailed insight into the structure of the recovered polyols, while GPC confirms molecular weight reduction and homogeneity. During the reaction, controlled volatilization of excess reagents or by-products may occur, which can be minimized or recovered under reduced pressure conditions.

This review highlights recent developments in the glycolytic recycling of PU waste, emphasizing environmentally benign protocols aligned with green chemistry principles. The process not only reduces dependency on fossil-based raw materials but also enables a circular economy approach to polymer sustainability. Continued research is essential to scale up these methods and integrate them into industrial waste management systems.