Molecular dynamics simulation of the effect and mechanism of doped nano-ZnO on the diffusion of water molecules in polypropylene

Abstract

Polypropylene (PP) is an environmentally friendly material with excellent insulating properties, making it of significant value in ultra-high-voltage cable applications. However, in practical applications, the diffusion of water molecules within cables accelerates the formation of water dendrites, which leads to the degradation of insulation performance. This study employs molecular dynamics simulation to investigate the effect of ZnO nanoparticles on the diffusion behavior of water molecules within polypropylene, and the models of unmodified and ZnO nanoparticles-doped polypropylene with varying water content are established to explore the intrinsic mechanisms at the microscopic level. The results demonstrate that the doping of ZnO nanoparticles increases the number of hydrogen bonds in the system, which increases the interaction energy between water molecules and polypropylene, effectively decreasing the water molecule diffusion coefficient. However, as the water content increases, the diffusion capability of water molecules strengthens. Additionally, an interface model of ZnO/water-containing polypropylene is created to analyze the distribution and trends of water molecules at the interface through the trajectory of their center of mass and relative concentration. This study offers reliable theoretical support for the advancement of polypropylene materials.