Study On The Synthesis Of High Trans-1,4-polybutadiene By Multilithium Initiator System

In recent years,with the increasing demand of the tyre performance,it's more and more important to synthesize the rubbers that possess special structure to make an all-round performance.Among these rubbers,the star-shaped rubber has increasingly attracted extensive attentions for its low temperature resistance,wet skid resistance,low rolling resistance,good processability,cold flow property resistance and so on.Preparing star-shaped rubber by the multilithium initiator is an effective method.Recent years along with the understanding on the correlation of structure and property deepen increasingly,it is found that HTPB,which has good stretching stress,high-hardness,good abrasion performance,good fatigue resistance and high tensile strength,should be used as compounding rubber in tire tread industry for improving tire performance.So it is the ideal rubber compound for developing radial tire.The multilithium initiator is prepared by divinylbenzene(DVB) and n-BuLl at proper temperature,which is reacted in cyclohexane solvent with isoprene for improving solubility and THF as polar additive for improving the reaction rate.The multilithium initiator has the advantages of simplified preparation technology,short synthesis time,low cost and good solubility in non-polar solvent.The results show that the multilithium initiator can be used to realize the design of molecular weight of the polymers and the synthesis of star-shaped polymers with broad molecular distribution.Barium salt of di(ethylene glycol) ethylether(BaDEGEE) and barium salt of tetrahydrofurfuryl alchol(BaTHFA) were synthesized in this paper,and then star-shaped high trans-1,4-polybutadiene(s-HTPB) was synthesized with organic barium/triisobutylaluminum/multilithium(Ba/Al/Li) as the initiation system and cyclohexane as the solvent.The effects on the polymerization and polymer microstructure were systematacially studied,and the polymerization kinetics of butadiene was determined by dilatometer method.The microstructure,glass transition,molecular weight and molecular weight distribution of HTPB were analyzed and characterized by FT-IR,NMR,DSC,GPC respectivelly.It was found that:s-HTPB with broad molecular distribution had been synthesized with Ba/Al/Li initiation system.The trans-1,4 content should be controlled by adjusting the dosage of initiator and the polymerization temperature.The trans-1,4 content increased gradually with the increasing of Al/Li,and the reaction rate of the polymerization decreased at the same time.the reaction rate of the polymerization increased gradually with the rise of the temperature,and trans-1,4 content decreased at the same time.Besides,series of star-shaped block copolymers that containing crystallizable HTPB chain segment were synthesized,HTPB had one Tg which appeared at -90℃～-80℃.The Tg of star-shaped block copolymers containing polyisoprene was between the Tg of HTPB and polyisoprene,while block copolymers containing polystyrene showed two Tg which appeared at-90℃～-80℃and 65℃～85℃.