Rigid Polyurethane Foams from Cardanol: Synthesis, Structural Characterization, and Evaluation of Polyol and Foam Properties

Global efforts to find renewable feedstocks for the chemical industry are aimed at replacing fossil reserves and a reduction in global warming by employing environmently friendly technologies (green chemistry approaches) for specialty chemical manufacturing. Cardanol, obtained as a byproduct of the cashew processing industry, is an important renewable resource and a unique phenolic compound carrying a 15-carbon side chain in meta position with varying degrees of unsaturation. In this work, the synthesis of new biobased polyols for rigid polyurethane (PU) foams through oxidation of side chain unsaturation is reported using the environmentally benign reagent hydrogen peroxide. Polyols with hydroxyl values in the range of 350-400 mg KOH/g were prepared through epoxidation followed by hydrolysis and characterized for structure using IR,H-1-NMR, C-13 NMR, and mass spectroscopic techniques. The foaming characteristics were studied, and the polyols were successfully used in making rigid polyurethane foams with good physical and mechanical properties. The foams were characterized for density, compressive strength, morphology, and viscoelastic properties. The properties are compared with that of foams prepared using standard petroleum-based polyols.