Relationship between Branched Structure and Viscoelastic Properties of Highly Branched Polyethylene Derived by Monte Carlo Molecular Simulation and the BoB‐Rheology Simulation Methods

Abstract

AbstractIn this report, it is verified by the simulation what kind of difference can be caused in the molecular structure and the viscoelastic property by the difference in the manufacturing process of the high‐pressure low density polyethylene, that is, autoclave (or vessel) process and tubular process. The Monte Carlo simulation developed by Tobita is used as the molecular structure simulation. The molecular simulation is performed assuming a five tanks‐in‐series model, which allows one to investigate a wide variety of reactor operations, from the condition closer to the tubular process to the autoclave processes systematically. The branched structure is quantitatively evaluated by the parameter known as priority and seniority (segment depth). The viscoelastic simulation is based on the branch‐on‐branch rheology (BoB‐rheology) model developed by McLeish et al. It is found that the long‐chain branched structure of the molecule becomes more complicated in the autoclave process, and then, the strain hardening property of extensional viscosity becomes larger than that for the tubular process.