Study Of Solution Styrene And Butadiene Rubber Modified By Novel Structure Modifiers

It is well known that the solution styrene and butadiene rubber(SSBR) is produced fromanionic polymerization by organolithium initiators in the presence ofpolar modifiers, such asamines,ethers or alkoxyl metal compounds which are needed to adjust the vinyl content ofthe diene polymers. The key synthesis technology of SSBR is the selection of structuremodifiers which is increasingly attracted extensive attentions, and it has a direct effect onstructure and properties of SSBR.In this thesis, self-made asymmetric ethers and sodium alkoxides are used as modifiers inanionic copolymerization of styrene and butadiene in the cyclohexane and hexane mixingsolution with n-butyllithium as the initiator, in which asymmetric ethers are synthesizedfollowing the Darzens method include ethyl morpholinoethyl ether(EOEM) andtetrahydrofufury ethyl ether(ETE), sodium alkoxides include sodium salts of tetrahydrofufuryalcohol and sodium salts of morpholinoethoI. Furthermore, this thesis studies systematicallythe kinetic behavior of the copolymerization and the coupling reaction. The microstructure,molecular weight and its distribution of the copolymers are well discussed in detail. Inaddition, the physical mechanical properties and the dynamic mechanical analysis(DMA) arealso investigated.The kinetic behaviors of the copolymerization,the relationship between polymercomposition and conversion at different modifier dosages,different initiation temperature arestudied. And the value of the monomer apparent reactivity ratios under different conditions isobtained. The kineties research indicates that the polymerization speed increases fast with theadding of the modifiers, and the value of the butadiene apparent reactivity ratios(r₁) declinesand the styrene apparent reactivity ratios (r₂) augments accordingly when the dosage ofmodifiers increased, so the styrene monomer is randomized along the polymer chain to formrandom SSBR. However, the value of r₁ augments and that of r₂ declines when the initiationtemperature rises from 50℃to 70℃.The microstructure research shows that the regulation ability of the modifiers are sostrong that the 1,2-content of polybutadiene in SSBR can be modified from 20ï¼…to 80ï¼…easily by altering the modifier concentration and the initiation temperature ranges from 30℃to 70℃; And the randomizers regulation ability decreased in following order: THFAONa＞ MEONa＞ETE＞EOEM; The regulation ability of the modifiers is getting smaller as theinitiation temperature rises, and the initiation temperature has more significant influence onthe regulation ability of EOEM and MEONa than that of ETE and THFAONa. The researchshows that the adding of the modifiers, such as ETE,EOEM and MEONa, have littleinfluence on the molecular weight and its distribution. However, THFAONa has a significantinfluence on them, and the molecular weight distribution of SSBR ranges from 1.04 to 1.65with the changing of THFAONa/BuLi(mol ratio) ranges from 0 to 5.0 at 50℃. It is found thatcoupling efficiency decreased with increasing modifier dosages or raising the initiationtemperature, and the sequence to the effect of the coupling efficiency is as follows:THFAONa＞MEONa＞ETE＞EOEM.Furthermore, the results of the physical properties show that the resulting productspossesse good physical and mechanical properties. The products in MEONa/BuLi system orTHFAONa/BuLi system have both high wet skidding-resistance and low rolling-resistanceproperties, which are valuable for using in making automobile tire treads, and the products inETE system have excellent wet skidding-resistance properties which are valuable for using inmaking race tire treads and rain tire treads.