The effect of HMMM in a hybrid polymerization comprising free radical polymerization

Compositions of hexamethoxymethylmelamine (HMMM)-ether polyol and acrylate can be cured by a hybrid polymerization composed of condensation polymerization and free radical polymerization at higher temperatures in the presence of a latent acid catalyst, but without a free radical initiator. The initiating radicals of the free radical polymerization come from the decomposition of adventitious peroxides. It has been proved that HMMM plays a very important role in this hybrid polymerization. HMMM is not only a crosslinking agent of polyol, but also acts as a catalyst of formation and decomposition of the peroxides of the active methylene groups of ethyl polyol. The hybrid polymerization system provides a synergetic effect on the curing reaction, partly ascribed to the thermochemistry complementary between endothermic condensation polymerization and exothermic free radical polymerization. This paper presents a review of this research.