Abstract
AbstractPurified, gel free butadiene‐styrene copolymers were prepared by emulsion polymerization with butadiene contents of 80, 55 and 30 weight %. Radiation behavior of these materials at 30°C was independent of dose rate in the range 0.04‐0.46 Mrad/hour and the scission‐crosslinking ratio was about 0.40 for all copolymers and was independent of total dose. Extrapolated sol fractions at infinite dose, intrinsic viscosities of irradiated polymers and Mn in the pre‐gel region gave mutually consistent estimates of this ratio. G(crosslink) was 3.4. At the relatively low doses studied, intra‐molecular crosslinking was evident only with the high styrene content polymer. Active sites for intermolecular crosslinking are thought to be allylic to chain double bonds, whereas vinyl groupings may be involved in intramolecular crosslinking.
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