Biobased Aromatic-Aliphatic Polyols from Cardanol by Thermal Thiol-Ene Reaction

Abstract

Cardanol is a natural phenol which is obtained from high vacuum distillation of cashew nut shell liquid. It contains a hydrocarbon chain of 15 carbon atoms in the meta position, either with one, two or three non-conjugated double bonds. This article describes thermal thiol-ene reaction to synthesize new cardanol-based polyols for polyurethanes with aromatic-aliphatic structure. Phenolic hydroxyl group was blocked by alkoxylation and 2-mercaptoethanol was added to the double bonds of propoxylated cardanol. The resultant product is a mixture of polyols that may contain one, two, three or four hydroxyl groups, as a function of the number of double bonds reacted with 2-mercaptoethanol. Similar polyols, but with much higher functionality, were also synthesized from condensation of cardanol-based novolacs with formaldehyde. These cardanolbased polyols were further utilized to prepare rigid polyurethane foams (PUs) with excellent physical and mechanical properties, useful for various applications in chemical and food industries.