Self-assembly behavior of temperature sensitive additive in polypropylene matrix: Molecular dynamics simulations

Abstract

In this paper, material studio software was used to simulate the self-assembly probability of N,N’,N”-tricyclohexyl-1,3,5-benzenetricarboxylamid as a temperature-sensitive additive in molten polypropylene. 15 cells of PP were simulated based on RSM (CCD) designed, with various temperature of 200–300 °C, PP chain length of 20–300 repeat unit and additive content of 0.5–2% wt. as independent variables. Additive molecule diffusion coefficient and distance between a pair of additive molecules were considered as responses. To justify the change in molecular diffusion coefficient, the free volume of the system and polymer chain mobility were calculated for each simulated cell. It is found that temperature directly affects the diffusion coefficient of additive molecules through free volume and mobility of polymer chains, while it had little effect on the intermolecular distance. The diffusion coefficient and intermolecular distance of additive decreased by increasing additive content. A longer polymer chain with more free volume increased slightly the mobility of additive molecules, but had no effect on their distance. In general, self-assembly of additive molecules is more likely at higher temperatures and optimal additive contents. Optical microscopy observations verify the simulation results.