Synthesis and deblocking of cardanol‐ and anacardate‐blocked toluene diisocyanates

Methyl anacardate and secondary butyl anacardate were prepared from anacardic acid and corresponding alcohols and were used, in addition to cardanol, as blocking agents for 2,4‐toluene diisocyanate (TDI). Blocked diisocyanate adducts were characterized via nitrogen estimation, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy. The deblocking temperatures of the adducts were determined using an FTIR spectrophotometer in conjunction with the carbon dioxide evolution method. The gel times of hydroxyl‐terminated polybutadiene–TDI adducts also were determined. Deblocking temperature and gel time analyses revealed that cardanol‐blocked 2,4‐TDI deblocks at a lower temperature and at a higher rate compared with anacardate‐blocked adducts. In addition, it was found that the electron‐withdrawing ester group reduces the deblocking temperature of the adduct only when it is in solvated form. All adducts were waxy solids that were found to be soluble in polyether polyol, polyester polyol, and polyhydrocarbon polyols.