Studies on hybrid polymesization of hexamethoxymethyl melamine-polyol-acrylate

Research on the novel hybrid polymerization system of hexamethoxymethyl melamine (HMMM)-polyolacrylate-acid has been reviewed. The hybrid system involves a condensation reaction of HMMM and free radical polymerization of acrylate, although there is no free radical initiator in the compositions. It is suggested that active methylene groups can be oxidized to the corresponding hydroperoxide through a charge transfer complex (CTC) between HMMM and O-2 in the air. Catalyzed by acid, the hydroperoxide decomposes rapidly, generates free radicals and then initiates the free radical polymerization. There are some synergetic effects between the radical polymerization and condensation reaction. First, the curing rate could be enhanced greatly. Secondly, DSC trace. of the hybrid polymerization system demonstrates that there is obvious energy compensation effect in the system. The released energy of the free radical polymerization of acrylate can be transferred to the endothermic condensation reaction of HMMM. Thirdly, the properties of cured film, such as mechanical properties and solvent-resistance, are greatly improved. It is demonstrated that the improvement is caused by the formation of polymer alloys with IPN (Interpenetrating polymer network) structure in-situ via dynamic mechanical thermal analysis ( DMTA) and transmission electron microscope (TEM) An addition, acrylate can adjust the viscosity of the formulation and reduce the use of volatile organic compound (VOC) To make the formulation more flexible, some new compounds containing very active methylene groups and hydroxyl group such as diethylene glycol allyl ether and diethylene glycol benzyl ether were synthesized and used as the crosslinker-initiators in the hybrid polymerization system. To increase the shelf-time of the formulation, latent acid catalysts trans-2-hydroxycyclohexyl-p-toluenesulfonate and pyridine p-toluenesulfonate, were used as the source of acid in the hybrid formulations. The application of hyperbranched polymers in hybrid polymerization system is under study. Consequently, the hybrid polymerization system of HMMM-polyol-acrylate-acid is promising to formulate a high curing rate, low solvent content, energy conservation and high quality coating.