UV-curing behavior and properties of tri/di(acryloyloxyethyloxy) phenyl silane used for flame-retardant coatings

The silicon-containing multifunctional acrylates, tri(acryloyloxyethyloxy) phenyl silane (TAEPS) and di(acryloyloxyethyloxy) methyl phenyl silane (DAEMPS) were prepared by using the transetherification of phenyltrimethoxyl silane and dimethoxymethylphenyl silane with 2-hydroxylacrylate, respectively. The molecular structures were confirmed by FTIR, 1H NMR, 13C NMR and 29Si NMR spectroscopic analysis. The obtained TAEPS and DAEMPS as tri- and difunctional monomers were blended with a commercial oligomer epoxy acrylate (EB600) in different ratios to formulate a series of silicon-containing UV-curable resins. The viscosity of the resins reduced obviously while the photopolymerization rates according to the photo-DSC analysis greatly increased by the addition of monomers. The thermal degradation and flame-retardant behaviors of the cured films were evaluated by the thermogravimetric analysis and the limiting oxygen index (LOI) measurements, respectively. The char yields measured under air atmospheres increased extraordinarily with increasing the silicon content. The LOI values increased from 21 for EB600 to over 30 at 70 wt% monomer loading, demonstrating that the improved flame retardancy was obtained. The data from dynamic mechanical thermal analysis showed that TAEPS and DAEMPS have good miscibility with EB600. The crosslink density of UV-cured EB600/TAEPS film showed a greater increase along with the monomer content, compared with that of EB600/DAEMPS. The mechanical property measurement indicated that the addition of TAEPS led to an increase in elongation-at-break and a first increase and then decrease in tensile strength.