Glycerol as a Sustainable Source for Nonisocyanate Polyurethanes: Green Chemistry and Applications

The growing demand for more sustainable polymeric materials has driven significant interest in renewable sources. In this context, nonisocyanate polyurethanes (NIPUs) represent a promising alternative to conventional polyurethanes , as they eliminate the use of toxic isocyanates. Different synthetic routes for polyurethanes without isocyanate have been developed in recent years. Among them, the polyaddition of cyclic carbonates (CCs) and diamines has attracted particular attention. The availability of various biobased feedstocks for cyclic carbonate synthesis has led to growing research in this area. Biobased feedstocks for the preparation of cyclic carbonates (CCs) can be broadly categorized into four main groups: (i) vegetable-oil-derived feedstocks (e.g., triglycerides and unsaturated fatty acids); (ii) lignocellulosic-biomass-derived phenolic compounds, including lignin derivatives (e.g., vanillin and guaiacol), tannins, and cardanol; (iii) carbohydrates and polyols, such as glucose, sucrose, starch, cellulose, glycerol, sorbitol, and mannitol; and (iv) terpene-derived compounds, such as limonene and rosin (a diterpene-based natural resin mainly composed of abietane-type resin acids). Glycerol, a renewable, abundant, and low-cost byproduct of industrial processes such as biodiesel production, is an attractive candidate for cyclic carbonate synthesis. This review provides a comprehensive overview of the conversion of glycerol into cyclic carbonate precursors, especially glycerol carbonate and diglycerol dicarbonate, and their role in NIPU synthesis. Particular emphasis is placed on the application of NIPUs derived from these cyclic carbonates in foams, adhesives, and coatings. This article highlights the advancements in the synthesis, properties, and performance of glycerol-based NIPUs over the past decade. By showing the progress and challenges of using these biobased feedstocks, this review contributes to the ongoing research toward sustainable NIPUs.