Study On The Design, Preparation, And Properties Of Energy-Saving Tire Tread Composite

In recent years, in response to the rapid development of the automobile industry and the increasing shortage of oil resources, the requirements for high-performance automobile with safety, comfortable, and energy-saving properties have been more urgent, which means their tires should have low rolling resistance, high wet-skid resistance and good abrasion resistance. However, the three properties are difficult to be improved at the same time,(i.e., one or two properties are improved meanwhile another properties will be decreased), which are generally called "magic triangle" of the tire performance. For the greatest balance of "magic triangle", the design of molecular structure should be made a breakthrough. Therefore, the design of molecular structure of energy-saving rubber is one of research focuses. In addition, a new type of crystalline polymer, called trans-1,4-polyisoprene (TPI), has good molecular chain flexibility. The vulcanized rubber of TPI has low internal friction loss and low rolling resistance. However, the energy-saving mechanism of TPI used in the tire tread rubber has not been reported. Based on the investigation of the green tire tread, the energy-saving mechanism of TPI is another of research focuses.In the first part (Chapter3), the preparation, characterization, structure, and property of end-functionalized star-shaped SSBR (S-SSBR) was investigated. The star-shaped SSBR with tert-Butylchlorodiphenylsilane (TBCSi) on the one end of macromolecular (TS-SSBR) were prepared by anionic polymerization using a multifunctional organic lithium initiator. The molecular structure parameters of TS-SSBR and S-SSBR were characterized and the end-capping efficiency was calculated. The results showed that the carbon black (CB) dispersion in the TS-SSBR composite was improved due to the reduction of free molecular chain and the stronger adsorption between carbon black and TBCSi. The interaction between carbon black and TS-SSBR was increased greatly and the internal friction of TS-SSBR composite was reduced, which made TS-SSBR composite had good mechanical properties, high wet-skid resistance and low rolling resistance. Therefore, TS-SSBR can be used as the tread of green tires.In the second part (Chapter4), we designed a new miktoarm star-shaped polybutadiene-Sn-poly(styrene-butadiene) rubber. The kind of miktoarm star-shaped rubber which had the coupling structure, the modification structure and the integration structure at the same time was prepared by using different coupling processes and different initiators. The molecular structure parameters of miktoarm star-shaped rubber were characterized and the coupling efficiency was calculated. The performance of miktoarm star-shaped rubber composites filled with CB were studied and compared with those acquired from the traditional blend consisting of star-shaped styrene butadiene rubber (S-SSBR) and butadiene rubber (BR). The results showed that the miktoarm star-shaped rubber, which prepared by two-step coupling technic and1,1-diphenyl hexyllithium (DPHLi), presented better CB dispersion, good mechanical property, lower internal friction, lower dynamic compression heat built-up, higher tanδ at0℃and lower tan8at60℃. It was envisioned that the miktoarm star-shaped rubbers with1,1-diphenylhexyl groups at the molecular ends had good balance among high wear resistance, high wet-skid resistance and low rolling resistance. Therefore, the miktoarm star-shaped rubber can be used as preferred green tire tread rubber.In the third part (Chapter5), the comprehensive performance for SIBR2505filled with the same volume fraction of carbon black (CB), precipitated silica and carbon-silica dual phase filler (CSDPF) were investigated. The interaction between the fillers and the rubber matrix was characterized by the Mooney viscosity test, the bound rubber content and solid-state1H low-field nuclear magnetic resonance (NMR) spectroscopy. The filler network structure was characterized by rubber processing analyzer (RPA) and dynamic mechanical thermal analyzer (DMTA). The results showed that for the characterization of filler-rubber interaction, the mooney viscosity test, the bound rubber content and solid-state1H low-field nuclear magnetic resonance (NMR) spectroscopy had a highly correlation:CB had the strongest filler-rubber interaction with rubber matrix. For the three different fillers, the composite filled with silica had the minimum tan5peak and highest storage modulus under the rubber state due to silica had the strongest filler network structure in the SIBR2505. The composite filled with CB had the best wear resistance and the highest tensile strength, but it also had the highest internal friction loss and compression heat build-up.In the fourth part (Chapter6,7), we studied the comprehensive performance of trans-1,4-polyisoprene (TPI) composite as energy-saving tire tread rubber used in emulsion styrene butadiene rubber (ESBR) and natural rubber (NR). Firstly, the crystallization of TPI structure and crystallization conditions was investigated. It was found that the crystallization time of TPI was about3hours and the crystal size was more than100μm when the temperature was35℃.The crystallization time of TPI was about10minutes and the crystal size was about20μm when the temperature was23℃. Secondly, the comprehensive performance of TPI/ESBR, star-shaped SSBR/ESBR, TPI/NR and star-shaped SSBR/NR were investigated by using the best processing technic, and the energy-saving mechanism of TPI used in tire tread rubber was explored. The results show that the TPI crystal was existed in the TPI/ESBR compound and TPI/ESBR composite filled with CB. With the increasing of the temperature, the transformation of TPI from crystal to amorphous in TPI/ESBR compound and TPI/ESBR composite was investigated by using rubber processing analyzer (RPA). But the TPI crystal was not existed in the TPI/NR composite which prepared by the best processing technic. The energy saving effect of adding25phr TPI was the same as that of adding40phr star-shaped SSBR into ESBR. However, the energy saving effect of adding15phr TPI was the same as that of adding25phr star-shaped SSBR into NR. The energy-saving mechanism of TPI used in ESBR, which was’TPI like filler to enhance the properties when it was crystal; TPI like rubber to decrease the internal friction when its crystal was melting’, was firstly put forward.