Flow Modification Effects and Mechanisms of Silicone Powder and PEG on UHMWPE/HDPE Blends: Insights from Experimental and Molecular Dynamics Simulations.

Abstract

The high melt viscosity and poor flowability of ultrahigh molecular weight polyethylene (UHMWPE) hinder its spinning production efficiency and industrial-scale processing. In this study, a blend of UHMWPE and high-density polyethylene (HDPE) was modified by incorporating silicone powder and polyethylene glycol (PEG). By integrating experimental characterization with molecular dynamics simulations, this study investigates the effects and underlying mechanisms of flow modification induced by the individual and synergistic incorporation of PEG and silicone powder into UHMWPE/HDPE blends at both macroscopic and molecular levels. Experimental results showed that 1 wt % PEG provided the most significant modification effect on the UHMWPE/HDPE blend. Compared to the unmodified UHMWPE/HDPE blend, the processing torque and flow activation energy decreased by 22.1% and 34.57%, respectively, and the melt flow rate increased by 48.04%. However, a slight reduction in tensile properties was observed, with the tensile strength decreasing by 5.09%. Molecular dynamics simulations revealed that the addition of 1 wt % PEG notably enhanced the overall mobility of the molecular chains in the UHMWPE/HDPE blend, leading to the highest free volume fraction and diffusion coefficient, thus improving flowability. However, the intermolecular interactions within the blend were relatively weak, resulting in lower cohesive energy density and interaction energy, which, in turn, reduced mechanical properties. The experimental and simulation results are in good agreement and provide valuable insights into the modification effects and mechanisms of different flow additives, offering guidance for the selection and optimization of modification formulations for UHMWPE.