Sustainable Synthesis of Polyurethane Using Hydroxyl-Terminated Polybutadiene (HTPB) Derived From the Degradation of Butadiene Rubber with Fatty Alcohol

Abstract

Polyurethane (PU) is one of the most commonly used plastics, typically synthesized from diisocyanates and polyols derived from non-renewable or unsustainable sources. This study proposes a synthesis route for polyurethanes that originates from bio-based polyols. The polyols were obtained through the metathesis depolymerization of butadiene rubber using fatty alcohol and Hoveyda-Grubbs second-generation catalyst (HG2), resulting in hydroxyl-terminated polybutadiene (HTPB). FT-IR and GPC analyses confirmed the successful synthesis of polyols, indicating molecular weights between 535 and 2200 g/mol. Three polyurethanes (PU1, PU2, and PU3) were synthesized using these bio-based polyols, while a fourth polyurethane (PU0) was produced with polyethylene glycol as a standard polyol for comparative property analysis. FT-IR analysis identified the characteristic signals and functional groups of the polyurethanes. TGA and DSC evaluated the thermal properties of the polyurethanes, revealing decomposition temperatures (Tmax) between 300 and 450°C. PU materials were practically amorphous, as shown by XRD. SEM micrographs illustrated the varying morphologies of the polyurethanes, providing deeper insights into their properties. This synthesis process is vital for recycling rubber waste, transforming it into hydroxy-terminated compounds, HTPB, or polyols using vegetable oils and renewable resources. When integrated into PU synthesis, these compounds promote the development of sustainable materials and significantly contribute to environmental conservation and the sustainable production of adhesives, paints, and coatings, among other valuable products.