Abstract
Ultrasonically initiated emulsion polymerization of styrene was carr ied out in the presence of the volatile hydrogen radical scavenger CCl_4. With ad dition of CCl_4 the polymerization rates first increased and then decreased.T he increase of H_2O_2' yield and the decrease of pH and the produc ed polystyrene's m olecular weight in the presence of CCl_4,and the effect of non-volatile hydrog en radical scavenger on ultrasonically initiated emulsion polymerization of styren e indicates that the observed enhancement can be explained as follows.CCl_4 ma y enter cavitation bubbles and further react with hydrogen radicals (·H) from the sonolysis of water to produce new radicals ·CCl_3,so as to reduce the recomb in ation of ·H and ·OH.Therefore more radicals would be present in the systems f or initiating polymerization.In addition,the effect of CCl_4 on ultrasonicall y initiated emulsion polymerization of methyl methacrylate(MMA) was studied.The r esults showed that CC l_4 did not significantly enhance the ultrasonically initiated emulsion polymer izatio n rate of MMA due to high vapor pressure and solubility of MMA,which would redu ce the efficiency of CCl_4 scavenging ·H.
Published Version
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