Structures And Properties Analysis Along With Molecular Simulation Study Of Sbr With Medium Bound Styrene Content

The elastomers for tire tread applications are supposed to have features such as excellent wet skid resistance, low rolling resistance, and high wear resistance to assure safety, energy efficiency, durability, and environmental friendliness of the vehicles. In the present thesis, the following works were completed concerning micro-structural characteristics and macro-performance of tire tread rubber.1. Styrene butadiene rubber (SBR) is the most consumable synthetic rubber. A large amount of automobile tires have been made from SBR. The styrene/butadiene ratio is one of the fundamental factors for the material performance of SBR. By combining experiments and molecular simulations, three SBRs with different contents of bound styrene were studied and compared in this work. The atomistic models of these SBRs were built according to their 1H-nuclear magnetic resonance (1H-NMR) spectra results. The free volume, cohesive energy density (CED), mean square displacement (MSD), and glass transition temperature (Tg) of the SBR models were calculated with the aid of molecular dynamic (MD) simulation. The simulated free volume and Tg were consistent with positron annihilation lifetime spectra (PALS) and dynamic mechanical thermal analysis (DMTA) results, respectively. What’s more, a linear fit of the calculated Fsim and tan δ values of the vulcanizates at 0 and 60℃ from DMTA spectrum was performed to try to build the connection between the simulated micro-structural characteristics and macro-performance. The present work hopes to provide some theoretical guidance to the chain structure design of SBR for tire tread applications.2. With increase of requirements for environment protection, the tire tread materials must "go green". In this work, the effects of carbon black and sulphur contents on the material performance were studied concerning a new product SBR 1756 which has medium bound styrene content. The present work hopes to provide some references for its application in high-performance green tires.3. Compositions of several tire tread materials were analyzed by Fourier transform infrared (FTIR) spectroscopy, NMR, thermal analysis, electron microscopes, and etc. The components of matrix, reinforcement fillers, curing characteristics of the materials were achieved, as well as their preliminary relationships with the material performance. The present work hopes to offer some useful information for composition analysis of vulcanized rubbers and compound design of tire tread rubber.4. It is of importance to reclaim and reuse old tires and other waste rubber products for both environment protection and resource conservation. In this work, molecular simulation was employed to investigate the diffusion of reclaiming oil in rubber matrix. The structures of polyisoprene and cyclohexane molecules were constructed. The results of MD simulation showed that the diffusion coefficient (D) of the cyclohexane molecules increased as the temperature rised, especially when the temperature was above 400 K, while the change of pressure did not affect it significantly. The fraction of free volume (FFV) exhibited a similar trend to that of D. The calculated Ds agreed well with the experimental results.