Study On The Design, Preparation, Structure, And Properties Of Molecular Structure Of Energy-saving SSBR And Its Nano-reinforced Material

Recently, with the demand of energy conservation and emission reduction in our country and the development of automotive industry in high-speed, security, energy-saving, and comfort, there are increased requirements of high-performance tire with good wet-skid resistance, abrasion resistance, and low rolling resistance. It should have new breakthrough in molecular structure and reinforced structure of rubber. As is well-known to us, the internal friction losses among macromolecular chains and relaxation characteristics are the main factors. Therefore, the design of molecular structure of energy-saving rubber is the one of research focuses. Besides, the optimization of reinforced structure of rubber is the problem to be solved. In tire industry, carbon black is usually used for filling in tire tread material to get good comprehensive properties. However, it is obtained by incomplete combustion or thermal decomposition of petroleum, so the development of new material with low heat build-up and independent of petroleum resource is the urgent task, which has great significance of relieving the petroleum shortage, improving the air surrounding, and achieving the sustainable development. Silica, a high reinforcement and low heat build-up filler, is gradually popular in rubber industry, but it still shows easy-aggregation and weak interaction with rubber matrix. In this paper, we try to improve the silica-dispersion and its interfacial interaction with matrix and achieve the energy-saving and emission-reduction through the design of molecular structure and nano-filler reinforcement.In this study, we prepared the star-shaped solution-polymerized styrene-butadiene rubber (SSBR) by pilot plant test. Secondly, the technique for organic modification on the surface of silica and its effect were studied, including the preparation of SSBR/SiO₂ co-coagulated rubber as well as the physical properties, dynamic properties, and microstructure of co-coagulated rubber filled with silica or silica/carbon black. Thirdly, the end-functionalized SSBR had been successfully polymerized, and then the condensation mechanism between end-group and silica together with the overall properties of silica-filled composites were studied in detail. Last, the composite particle namely elastomer grafted onto the surface of silica particle had been prepared successfully.In the first part, the polymerization technique for star-shaped SSBR in the increased step of 5L, 10L, and 200L vessels had been developed. The problems such as high styrene content, incomplete purification, low random degree, and unstable polymerization temperature, were all solved. Twelve vessels of star-shaped SSBR met the qualification of tire tread material with high strength and low energy-consumption. The properties such as high-speed, comfort, oil-saving, and emission-reduction of automotive tire prepared by star-shaped SSBR in the pilot plant were obviously superior to those of normal tire. From laboratory testing to pilot plant, the polymerization condition for star-shaped SSBR prepared by anionic polymerization was determined, and this would provide guide for other chapters in this dissertation and other researchers in tire industry.In the second part, we studied the organic modification condition of silica powder by silane coupling agent, the content of silane coupling agent, and the change of characteristic peak area of silica powder coated with silane coupling agent detected by FTIR at different temperatures. Through the measurement of organically modified silica powder after extraction, the condensation condition between the silane coupling agent and the hydroxyl groups on the surface of silica powder was determined. The mechanical properties, dynamic mechanical properties, and filler-dispersion of rubber filled with organically modified silica prepared on that condition are the best. Next, we prepared SSBR/SiO₂ co-coagulated rubber by co-coagulation. The co-coagulated rubber had good silica-dispersion, and its silica-filled composite exhibited better filler-mixing rate, filler-dispersion, interfacial interaction, and other comprehensive properties than the rubbers prepared by direct mixing. From the result of glass-transition characteristics it also showed that interfacial bonding had played an important part in the restricting the motion of macromolecular chains. At last, the overall properties of composites using the normal star-shaped SSBR and star-shaped SSBR co-coagulated rubber respectively as the matrix both filled with silica/carbon black doped filler at different ratios were studied in detail. As a whole, the doped filler had a synergic reinforcement. As the silica/carbon black ratio was 20/30, the rubber exhibited the highest bound rubber content, best mechanical properties and abrasion resistance. The composite using co-coagulated rubber as matrix displayed the characteristics of high strength, low rolling resistance, low heat build-up, low deformation, excellent flex resistance, and good filler-dispersion. Furthermore, its strong interfacial interaction could provide the wide application field for preparing the tread material used in the high-performance green tire.In the third part, the reactive silane coupling agent was added in the last stage of polymerization, and then the end-fimctionalized SSBR was prepared. The functionalization result had been characterized by ¹H NMR, FTIR, and EDS. The end-functionalized efficiency was also calculated by the peak area in ¹H NMR spectra. After its condensation with silica, the filler-polymer interaction and filler-dispersion had been improved, and the free terminals decreased. Its silica-filled composite showed the high bound rubber content, short relaxation time, low internal friction loss, good mechanical and dynamic properties, high wet-skid resistance and low rolling resistance. The research field could be widened when using different silane coupling agents to achieve end-functionalization. The end-functionalized SSBR had good reactivity with silica, and its silica-filled composite by reactive blending exhibited excellent comprehensive properties, which are proportional to end-functionalized efficiency.In the fourth part, silica was organically modified by KH570 to get the reactive silica particles. The monomers were styrene and isoprene, and the free-radical emulsion polymerization product was characterized by ¹H NMR, ¹³C NMR, FTIR, TEM, and EDS. The oxidation-reduction initiation system could solve the problem of low polymerization yield at low temperature. The C=C on the surface of modified silica particles had great different reactivity ratio from isoprene, so it was hard to get the high polymer component in composite particles. Both adding a small amount of styrene and prolonging polymerization time could effectively increase the polymer content and then the ideal SiO₂/PS/IR composite particles could be prepared. There was nearly no silica-aggregation and universally with the particle size of less than 30nm. This research finding will lay the foundation for achieving monodispersed nano-silica particles in rubber.