Study On Radical Grafting Reaction Of Polybutadiene

Acrylonitrile-butadiene-styrene copolymer(ABS)and high-impact polystyrene(HIPS)are widely used in household appliances,automobile industry,and building materials industry.The synthesis of ABS and HIPS is mainly based on free radical graft polymerization.The grafting rate of styrene(acrylonitrile)on polybutadiene rubber(PB)is one of the important factors affecting the performance of ABS and HIPS.Therefore,it is very important to study the mechanism of radical graft reaction.In this paper,a series of low molecular weight model polybutadiene(PB)was designed and synthesized by using living anionic polymerization method.The microstructure and molecular weight of PB was characterized by ~1H-NMR and GPC.The results showed that the prepared polybutadiene had a low molecular weight and a very narrow distribution,and its 1,2-structure content can be controlled.ThegraftingreactionofPBwithdifferent1,2-structures,2,2,6,6-tetramethylpiperidine-1-oxyl free radical(TEMPO)and benzoyl peroxide(BPO)as free radical initiator,was studied.The microstructure of the grafted PB was characterized by~1H-NMR.The results showed that when the content of 1,2-structure was low,the grafting reaction of PB was accompanied by free radical double bond addition and hydrogen abstraction reaction.With the increase of 1,2-structure content in PB,the proportion of hydrogen abstraction reaction increased.When the content of 1,2-structure content reached53.6%,the grafting reaction is basically a hydrogen abstraction reaction.With the increase of graft temperature,the proportion of addition reaction increased.When the content of1,2-structure was 53.6%,the ratio of PB addition to hydrogen abstraction increased to 1:2.In addition,the grafting reaction of trans-1,4-and cis-1,4-polybutadiene was studied.In the thermally induced grafting reaction,the grafting reactions of trans-1,4-and cis-1,4-polybutadiene is all hydrogen-absorption reactions,and the amount of addition reaction increased with the increase of temperature.After adding BPO,the grafting reaction of trans-1,4-polybutadiene is still dominated by hydrogen abstraction,but the high cis-1,4-polybutadiene gradually changes from hydrogen abstraction to addition reaction.