Structural Design And Preparaton Of Low VOC Coupling Agents Facing Green Tires

Coupling agent is one of the key factors to achieve the dispersion of silica and construct the interface between the filler and the rubber matrix,which is the core technology of“green tires”.However,the traditional coupling agent Si69 used in the“green tire”not only produced a large number of volatile organic compounds（VOC）,but also had a very limited effect on improving the silica dispersion,which seriously affected the working environment of tire enterprises and the reinforcement effect of silica.In view of the above problems,based on the structural design of coupling agents,a series of new silane coupling agents containing polyether long alkyl chain were synthesized,which not only reduced the VOC emissions but also significantly improved the dynamic performance of the“green tire”.Furthermore,in order to alleviate the shortage of petroleum resources and reduce the dependence of coupling agents on petroleum fossil resources,a new bio-based coupling agent was designed and prepared by introducing bio-based monomers.By adjusting the blending ratio of the coupling agents,a new strategy for the popularization and application of bio-based coupling agent in“green tire”was provided.The main contents of this thesis are as follows:（1）Six new low VOC coupling agents M₁-Si69～M₆-Si69（the coupling agent Si69 with one polyether long alkyl chain was abbreviated as M₁-Si69）with different numbers of polyether long alkyl chains were synthesised and analyzed.The charactrization of the silica modified by coupling agent demonstrated that the coupling agent can still form chemical binding with the silicon hydroxyl group of silica after grafting polyether long alkyl chain.At the same time,the synthesized low VOC coupling agent M_x-Si69（X=1,2,3,4,5,6）applied to silica/solution polymerized styrene butadiene rubber（SSBR）was studied,which proved that the coupling agent M₂-Si69 can significantly reduce the agglomeration of silica in nanocomposites and the rolling resistance of tires.By calculating the amount of ethanol collected in the reaction and the test of rolling resistance confirmed that M₂-Si69 can reduce VOC emission by about 70%and save more than 20%energy loss of the tire.（2）In order to further reveal the influence of non-rubber content of natural rubber on the properties of silica/natural rubber（NR）nanocomposites,the isoprene rubber（IR）nanocomposites,which possessed the same structural unit but without non-rubber content were studied in this research.The characterization of vulcanization parameters confirmed that the non-rubber content in the natural rubber can promote the vulcanization of silica/NR nanocomposites and improve the crosslinking density of the composites.The microstructure of the nanocomposites demonstrated that the non-rubber content could achieve a better silica dispersion in the rubber matrix.In addition,the results showed that the non-rubber content would reduce the efficiency of coupling agent Si69 in silica/NR nanocomposites.Then,the low VOC coupling agent M_x-Si69（X=1,2,3,4,5,6）was applied to silica/NR nanocomposites,and the performance of the silica/NR nanocomposites were characterized and analyzed.The research demonstrated that the polyether segment of M_x-Si69 would form a competitive relationship with non-rubber content by hydrogen bonding,which improved the modification effect of coupling agent on silica and reduced the filler network in NR nanocomposites.Compared with the traditional coupling agent Si69,M₁-Si69 showed better dynamic performance in silica/NR nanocomposites,which can save more than35%energy loss of the tire and improve the wet skid resistance of the tire by more than 23%.Moreover,the coupling agent M₁-Si69 can reduce the VOC that generated from the coupling agent modified silica by more than 50%.（3）In order to respond positively to the“double carbon”strategy proposed by China,the bio-based monomer Cardanol Polyoxyethylene Ether（CPE）was used in the research of the“green tire”coupling agent.The analysis of the CPE modified silica（CMS）demonstrated that the CPE could modify silica by hydrogen bonding and chemical grafting.The change of sulfur and CPE heated at a certain temperature proved that the unsaturated double bond of CPE can be vulcanized.However,using CPE directly is not as good as we expected.Then,the CPE was modified by sulfhydryl click and sulfur vulcanization to obtain a sulfhydryl-containing coupling agent MPCPE and a polysulfide coupling agent SCPE.The chemical structure of the synthesized coupling agent was studied and confirmed.In addition,the co-vulcanization of the coupling and rubber matrix was also characterized.Then,bio-based coupling agents MPCPE and SCPE were applied to silica/rubber nanocomposites.The properties of silica/rubber nanocomposites were tested and studied,which proved that the coupling agent SCPE possessed the potential application value,which can significantly improve the dispersion of silica.However,SCPE has large molecular weight and few effective functional groups,and there are still some deficiencies in industrial application.（4）In order to solve the problem of large molecular weight and few effective functional groups of SCPE,the scheme of mixing SCPE and TESPT in different proportions was designed and applied in the silica/rubber nanocomposites.The characterization of micromorphology of nanocomposites confirmed that the dispersion of silica in rubber matrix was improved by using SCPE and TESPT together.The performance measurement of rubber nanocomposites confirmed that the best combination ratio of SCPE and TESPT was 1:1.Then,the best combination ratio of SCPE and TESPT was applied to the formula of“green tire”,the dynamic performance measurement showed that SCPE and TESPT used at a ratio of 1:1 can reduce 12%energy loss of the tire and improve the wet skid resistance of the tire by 5.6%.Moreover,the determination of VOC content of coupling agent-modified silica confirmed that the combination of SCPE and TESPT with a ratio of 1:1can reduce VOC emissions by 45.8%.In conclusion,the combination of SCPE and TESPT provided a new application strategy for the popularization and application of bio-based coupling agent SCPE in silica/rubber nanocomposites.