The thermal dissociation of phenol-blocked toluene diisocyanate crosslinkers

Abstract

Several toluene diisocyanates blocked with various substituted phenols were prepared. They were characterized by elemental analysis, infra-red and 1H nuclear magnetic resonance spectroscopy. The deblocking temperatures were determined by use of infra-red spectroscopy and by carbon dioxide evolution methods. The thermal stability of the blocked isocyanate was less for the ortho-substituted phenols than for the para isomers. Dissociation temperatures were also reduced by electron-withdrawing groups. The dissolution temperatures of the adducts were determined in propylene glycol, poly(ethylene glycol) 400 and hydroxyl-terminated poly(butadiene). © 1993.