Effect Of Block Ratios Of Liquid Rubber And Mixing Sequence On Polybutadiene/polyisoprene Blend System

In this paper,the effect of block ratios of PB-b-PI liquid rubber and mixing sequence for the BR/IR/ PB-b-PI liquid rubber ternary blend were studied.The rheological properties of unvulcanized rubber,tensile properties and dynamic mechanical properties of vulcanized rubber were characterized.The relationship between block ratios of PB-bPI liquid rubber,mixing sequence and mechanical performance of rubber blend were discussed.The results provided ideas for designing better compatibilization strategies.The main work carried out in this study is as follows:In the second chapter,PB-b-PI liquid rubber with different block ratios and same molecular weight were prepared by sequential anionic polymerization.The microstructure analysis and molecular weight determination of the product by nuclear magnetic resonance spectroscopy and gel permeation chromatography showed that the synthesized PB-b-PI liquid rubber had similar molecular weight around 80000 and different block ratios varies from PB:PI=1:9 to PB:PI=9:1.In the third chapter,the researches were conduct in the blending system of polybutadiene /polyisoprene(BR/IR)with a ratio of 30/70,by adding PB-b-PI(PB:PI=1:9)to study the effect of addition amount of liquid rubber on the properties of the BR/IR rubber blend.It was found that with the increasing amount of PB-b-PI liquid rubber content from 0% to 7%,the storage modulus of unvulcanized rubber blend decreased.The rubber blend with an addition of 3% PB-b-PI liquid rubber had best tensile property,while it had the highest storage modulus in the dynamic mechanical test.However,when addition of PB-b-PI liquid rubber is beyond 5% to BR/IR blend,the tensile mechanical properties were worse and storage modulus was also lower in the dynamic mechanical test,indicating that 5% PB-b-PI liquid rubber was excessive and did harm to the mechanical properties of rubber blend.The fourth chapter studied the effect of block ratios of PB-b-PI liquid rubber and mixing sequence on BR/IR/PB-b-PI liquid rubber ternary blend system.It was found that when PB-b-PI liquid rubber was blended with BR and IR at the same time,the PB-b-PI liquid rubber with symmetric structure could compatibilize the BR/IR blend best,the storage modulus of unvulcanized rubber blend was the lowest and the mechanical properties of the vulcanized rubber blend was the best.When introducing the factor of mixing sequence into the research,such as mixing PB-b-PI with BR firstly and then mixing with IR,PB-b-PI liquid rubber with asymmetric structure has a greater impact on the properties of rubber blend.When the short block in the block copolymer is first blended with a compatible homopolymer,there will be better compatibilizing effect.Due to the change of block ratio,the migration ability of block copolymer is different.