Increasing the thermal conductivity of styrene butadiene rubber: insights from molecular dynamics simulation

Abstract

It is very important to improve the thermal conductivity of styrene butadiene rubber (SBR) which can widen its application. By employing reverse nonequilibrium molecular dynamics simulations in a full atomistic resolution, the effect of the composition ratio of styrene, temperature, and tensile strain on the thermal conductivity of SBR has been investigated in this work. The results indicate that the thermal conductivity of SBR gradually decreases with increasing composition ratio of styrene. This closely depends on the number of degrees of freedom and the diffusion coefficient of backbone atoms. Under the tensile field, the orientation of backbone bonds improves the thermal conductivity parallel to the tensile direction, but reduces the thermal conductivity perpendicular to it. Meanwhile, the thermal conductivity parallel to the tensile direction is enhanced with the strain rate while it is reduced with the composition ratio of styrene. Interestingly, there exists a linear relationship between the logarithm of anisotropy of the thermal conductivity and the orientation degree of bonds. Finally, the parallel thermal conductivity of the strained SBR first rises and then declines with temperature. This transition reflects a crossover from disorder to anharmonicity dominated phonon transport. Moreover, the transition temperature is gradually reduced with increasing strain which is attributed to the polymer orientation. In summary, this work provides some fundamental insights into the thermal transport processes in SBR with different composition ratios of styrene and temperature, especially under tensile strain.