Polyolefins Journal
With the collaboration of Iran Polymer Society

Molecular dynamics simulation for polyethylene crystallization: Effect of long chain branches

Document Type : Original research

Authors

Jieqi Wang 1
Li Zhao 1
Minju Song 1
Fenge Hu 2
Xuelian He 1

1 Shanghai Key Laboratory of Multiphase Material Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China

2 Guangxi Agricultural and Animal Husbandry Engineering School, Guangxi, China

https://doi.org/10.22063/poj.2021.2834.1173
Abstract
The influence of long branches on crystallization behavior has been studied by means of molecular dynamics simulations. Using two systems: polyethylene (PE) with long branches (LCB-PE) and PE without long branches (linear-PE) with the same molecular weight, we have examined the crystallization behavior of the two systems by molecular dynamics simulation. This paper explains the influence of long branches on the isothermal crystallization process and the non-isothermal crystallization process with similar initial interchain contact fraction (ICF) in terms of final ICF, crystal regions, crystallinity, concentration of tie chains and energy. It is found that the crystallization process is classified as two stages: the nucleation stage and the crystal growth stage. The existence of long branches is favorable for the first stage while unfavorable for the second stage. Knots that act as crystalline defects are excluded from the lamella, resulting in decreasing in regularity and crystallinity of molecular chains. From the perspective of potential energy and non-bond energy, LCB-PE has lower energy than linear-PE in the nucleation stage while the energy of linear-PE is lower than that of LCB-PE in the second stage. In short, the long branched chains inhibit the crystallization process.

Keywords

Molecular dynamics
crystallization
long branches
nucleation
tie chains
Subjects
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  • Receive Date 19 January 2021
  • Revise Date 26 February 2021
  • Accept Date 02 March 2021
  • First Publish Date 03 March 2021

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