Effects of vitrification on the isothermal polymerization of acrylate blends under radiation

摘要

The radiation-induced polymerization of some acrylate oligo-mers was investigated by means of FT-IR spectroscopy applied to films of various thickness that were cured under isothermal conditions.Different types of oligomers,one polyethyleneglycol diacrylate (PEGDA),one polyure-thane triacrylate (PURTA),and one epoxy diacrylate derived from bis-phenol A (EPDA) were selected for their contrasting networks properties,with a low,intermediate,and high T_g of the radiation-cured materials,respectively.In order to gain a deeper insight into the effect of gradual vitrification on the reactivity of the polymerizable systems,the conversion - dose profiles of the epoxy diacrylate were recorded at various temperatures.The dependence of the limiting conversion on the polymerization temperature was examined under various experimental conditions and compared with the conversion - T_g relation,which was deduced from dynamic thermo-mechanical analysis.The correlation between resulting T_g measured in the samples at maximal conversion for each curing temperature was shown to be slightly deviating from linearity.A phenomenological model of the reaction kinetics was shown to depict satisfactorily the observed photopolymerization profiles.From the well-determined T_g conversion relation,a semi-mechanistic kinetic model taking into account the gradual vitrification of the network can be foreseen.