The distinctions of the crystallization process of the interphase in polypropylene on untreated and different functional groups-treated CNTs by molecular dynamics simulation

Abstract

Polypropylene/carbon nanotube composites have attracted much attention for their remarkable electrical and mechanical properties. The key to achieve high performance is good interfacial properties between PP and the CNT. Hence, molecular dynamics simulation, a microscopic and direct method, was used to study the crystallization process of the interphase in a single PP chain on untreated CNT and different functional groups-treated CNT (CNT-OH, CNT-COOH, and CNT-NH2) modes. The simulation showed that the PP chain absorbed and ordered on the CNTs gradually with the increase in simulated time, resulting in regular g(r) and a decrease in the total valence energy, van der Waals energy, and interfacial energy. In particular, in comparison with others, the PP chain on the CNT-OH model had a more orderly g(r) and lower energies after 100 ps, showing a better interfacial interaction in the crystallization process. More specifically, at 2000 ps, the three peaks of the g(r) of the PP chain on the CNT-OH model were 183.78, 129.44, and 95.32, respectively, and the van der Waals and interfacial energies of the PP chain on the CNT-OH model were −167.937 and −869.20 kcal/mol, respectively. It was all attributed to the more orderly crystalline structure, stronger van der Waals forces and stronger phase interactions of the interphase in the PP chain on the CNT-OH model in the crystallization process.