Radiation graft copolymerization of styrene with acrylic monomers at high dose rate

The comparative investigation of radiation graft copolyme-- rization of following systems is performed: styrene-acrylonitrile (AN), styrene-methyl, methacrylate (MMA) and styrene-acrylic acid (AA) at considerabley differing radiation dose rates. The mixture of monomers has been grafted onto polyethylene films of low density of 70 μm thickness by irradiating the latter in the medium of liquid monomers. Copolymerization has been performed under the condition of a preliminary degassing of the irradiated system up to the residual pressure of 103Pa order. The following dose rates have been used: 0.08; 0.16; 0.25 Gy/s (γ-irradiation) and 102, 103, 6x103 Gy/s (accelerated electrons with E=1 MeV). The graft value determined in relation to initial film mass, constituted 15-25, 3-6 and 5-10% respectively for three investigated systems. The graft copolymer compositions have been determined by means of optical densities measured in IR-spectral region. It is established that radiation graft styrene copolymerization with AN and MMA is realized by radical mechanism up to I=102 Gy/s, the transition to ionic mechanism starts at I=103 Gy/s. For A-styrene system the limit of this transition is shifted into the higher dose rate region and contribution of graft ionic process has been found at I=6x103 Gy/s