Temperature Effect on the Conformation Transition of Ultra-high Molecular Weight Polyethylene/Polypropylene Blends Undergoing Continuous Volume Extensional Flow: A Mesoscopic Simulation

Abstract

Due to the multiformity and complexity of chain conformation under external flow and the challenge of systematically investigating the transient conformation and dynamic evolution process of polymer chains at the molecular level by means of present experimental techniques, a universal description of both chain conformation and dynamics with respect to continuous volume extensional flow (CVEF) is still absent. Taking into account the temperature effect, we performed dissipative particle dynamics (DPD) simulations with the particles corresponding to the repeat units of polymers over a wide temperature range and analyzed the correlation with the conformational properties of ultra-high molecular weight polyethylene/polypropylene (UHMWPE/PP) blend in response to the CVEF. With time evolution, the polymer chains become highly oriented parallel to the flow direction instead of the initial random coiling and self-aggregation. It is found that a high temperature is necessary for more substantial compactness to take place than low temperature. The low-k plateau and low-k peak in structure factor S(k) curves suggest a low degree of conformational diversity and a high degree of chain stretching. It is also concluded that the intra-molecular C-C bond interaction is the main driving force for the dynamics process of the chain conformations undergoing CVEF, where the motion of the alkyl chains is seriously restricted owing to the increase in bond interaction potential, resulting in a reduction of the difference in diffusion rates among alkyl chains..

Keywords

temperature effect / dissipative particle dynamics / ultra-high molecular weight polyethylene / polypropylene / volume extensional flow / chain conformation / blends

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