Study On Design,Synthesis And Performance Of Styrene/Diene Rubber Composites

With greater attention to environmental problems and energy conservation,an increasing need has emerged for preparing high-performance rubber composites in the field of rubber synthesis and processing.The effect of rubber structure on performance is mainly determined via the internal network and interfacial interaction between rubber and filler.Building the bridge that structure-internal network-performance has been a key strategy to develop high performance rubber composites.The styrene/diene rubber based on the living anionic polymerization is used widely to prepare the green tire tread rubber.The molecular chain compositions and cross-linked bond types are important components of cross-linked network of rubber materials.It is of great guiding significance for green tire tread compounds with“high modulus and low energy consumption”to clarify the relationship between changes of SSDR chain structure or cross-linked bond type,network structure and performance.Starting from the molecular structure design,this paper takes the styrene/diene rubber as the research object,and synthesizes the styrene/diene rubber matrix with clear structure based on the living anionic polymerization(LAP)method.Styrene/diene rubber composites reinforced with carbon black(CB)are prepared by combining the conventional compounding with vulcanization technology.The structure-activity mechanism between internal network structure and application properties of rubber is constructed and enriched via systematically studying the effects of matrix composition change,functionalized and topologized on the internal network structure and properties.In addition,the method of“rubber mechanochemistry processing”is developed to achieve the one-step construction of functionalized oxygen cross-linked network in the rubber after learning from the mechanochemistry.The main research results are as follows:(1)Three styrene/diene rubber matrix(named SBR,SIBR and SMR,respectively)are synthesized by LAP method.The corresponding rubber composites reinforced with CB fillers,namely CB/SBR,CB/SIBR and CB/SMR,are prepared via combining the conventional compounding with vulcanization technology,respectively.The effects of rubber matrix composition change on the internal network and interfacial interaction between CB fillers and rubber matrix,as well as the effects on viscoelastic performance and mechanical properties are studied.The results show that the influence of diene side length on rubber properties is related to the regulation of internal network strength,dispersion of CB fillers and the interfacial interaction between CB fillers and rubber.The presence of diene side chain length is not beneficial to the formation of cross-linked network,and the strength of cross-linked network decreases with the increase of diene side chain length.Both the dispersion in SIBR matrix and the interfacial interaction between CB fillers and SIBR with side methyl group are the best.Controlled by diene side group length on the strength of internal network and the interaction between CB fillers and rubber,CB/SBR compound without side group in diene has relatively low rolling resistance,high fracture toughness and recovery performance.CB/SIBR compound with side methyl group in diene has relatively high CB reinforcement factor,fracture toughness and damping properties but larger rolling resistance.CB/SMR compound with long side group in diene shows advantages in damping performance,but poor fracture toughness and recovery performance.The above research results have guidance for material design.The diene/styrene rubber with short side chain can be applied to the field of high strength materials.The diene/styrene rubber with long side chain is suitable for the field of damping materials.(2)SIBR integral rubbers with single terminal,double terminal and in-chain functionalized amino groups(α-SIBR,α,ω-SIBR and IC-SIBR),star topologized and single terminal functionalized star structure(S-SIBR and S-(α-SIBR))are synthesized by LAP method,respectively.The corresponding vulcanized rubber composites reinforced with CB fillers(CB/α-SIBR,CB/α,ω-SIBR,CB/S-SIBR and CB/S-(α-SIBR))are prepared by combining the processing method of rubber materials.The effects of functionalized or topologized on the internal network structure,interfacial interaction,viscoelastic performances and static mechanical properties of rubber composites are systematically studied.The results show that the viscoelastic performances of SIBR rubber with chain-end functionalization are improved,including the increase of storage modulus and the decrease of energy loss,whose rolling resistance decreasing by 16%-28%.The designing of topologized not only improves the viscoelastic performances of SIBR,but also improves the static mechanical properties,whose stress at 100%elongation increasing by 21%-60%.These CB/α-SIBR,CB/α,ω-SIBR,CB/S-SIBR and CB/S-(α-SIBR)rubber composites show potential advantages for the preparation of green tire tread rubber.Combining with non-equilibrium molecular dynamics(NEMD)results,the possible improving mechanisms of chain-end functionalized and topologized on SIBR integral rubber properties are clarified.The enhancement mechanism of chain-end functionalized on viscoelastic energy is related with the strong interfacial interaction between chain-end amine functional group and CB fillers,which leading to the constrained movement ability of the cross-linked network free-end and the formation of a strong filler network.The improved mechanism of topologized on viscoelastic performances and mechanical properties is that the improvement of interface interaction between rubber and CB fillers.And the star polymer chains are more likely to adsorb CB particles to form a second filler network,resulting in relatively high tensile modulus.(3)Combined with mechanochemistry,the“rubber mechanochemical processing”(RMP)method is developed.Applying shear force,the functionalized oxygen cross-linked network(-C-O-)and hydrogen bonding network are simultaneously introduced into the epoxidized butadiene rubber(EBR)when using dopamine as the crosslinking agent.The strength of oxygen cross-linked network is further enhanced under hot-pressing stimulus,and the further addition of sulfur can introduce multiple networks such as oxygen and sulfur covalent cross-linking network(-S_x-)and hydrogen bonding simultaneously.The effects of oxygen/sulfur covalent crosslinking network and hydrogen bonding on viscoelastic properties and static mechanical properties are investigated.The results show that compared with traditional sulfur cross-linked network,the oxygen cross-linked network makes EBR exhibit excellent tensile strength,ductility,damping properties and material stability.The introduction of reversible hydrogen bond network endows EBR with certain self-healing properties.Based on the reaction between epoxy group and phenol hydroxyl group in the RMP method,the cross-linked system is extended to lignin with polyphenol structure,CB and silica containing silane hydroxyl group.It is found that compared with traditional butadiene rubber composites,the compound prepared via RMP method greatly improved the interfacial interaction between lignin,CB or silica fillers and rubber matrix,further endowed the EBR composites with high mechanical properties and self-reinforcing properties.Meanwhile,the bio-derived lignin has the potential to be used as a reinforcing filler.