KINETIC-STUDY ON THERMAL POLYMERIZATION AND CROSS-LINKING OF PRE-IRRADIATED 1,4-BUTANEDIOL DIACRYLATE

The thermal polymerization and cross-linking of 1,4-butanediol diacrylate taking place after irradiation was followed kinetically in the temperature range from 60 to 140-degrees-C. Low conversions were reached by polychromatic pre-irradiation in the absence of any photoinitiating species. The disappearance of double bonds follows first-order kinetics, up to degree of conversion 0,4 < x < 0,5, and then proceeds up to high x values, according to a multiple relaxation phenomenon, characterized by the same mean relaxation lifetime as first-order kinetics. Activation parameters also were calculated. The present results on the decay of double bonds are discussed in the framework of the classical polymerization mechanism and in connection with previous kinetical data on the decay of radicals trapped in the same pre-irradiated monomer, obtained by electron paramagnetic resonance (EPR) measurements. Propagation and termination processes depend in the same way on the mobility of the vitrified polymerized network, both being diffusion-controlled.