Technical Paper Archive

This site contains all papers presented at Rubber Division, ACS Technical Meetings from 2000-2018. Meetings prior to 2000 are incomplete and papers are added as they are digitized.

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Quantifying Chemical Composition and Crosslink Effects on EPDM Elastomer Viscoelasticity with Molecular Dynamics

A45 aowang paper

Event: 198th Technical Meeting - Fall 2020
Location: Virtual
Date: October 19, 2020
Author: Ao Wang
Paper Number: A45

Price: $20.00

  • To understand the effect of chemical composition, crosslink density, and microstructure on the linear and non-linear viscoelasticity of ethylene propylene diene monomer rubber (EPDM), we carried out high-frequency oscillatory shear molecular dynamics simulations at varying shear strain rates. Sweeping through different EPDM compositions with varying ethylene, propylene and diene ratios, a positive correlation was observed between ratio of propylene monomer and storage modulus of EPDM in the high-frequency glassy regime. For small deformations in this regime, we found that the simplest measure of local molecular stiffness, namely the Debye-Waller factor, is predictive of storage modulus and loss modulus of 20 unique systems with distinct compositions and cross-link densities. Factors that reduce the Debye-Waller factor, such as cross-linking or increased PP content generally result in higher moduli. Remarkably, large-amplitude oscillatory shear simulations revealed that dissipation becomes strongly influenced by polymer entanglements, which results in divergent optimal compositions for small strain vs. large-strain applications of EPDM. We also utilized time-temperature superposition to extrapolate the results from computationally efficient high-strain rate simulations to lower strain rates, demonstrating predictive ability across a wide-range of strain-rates or temperatures. Our findings illustrate some of the important molecular mechanisms underpinning the constitutive behavior of elastomers and pave the way for multi-scale analyses linking composition and microstructure to performance.

    Papers from 198th Technical Meeting - Fall 2020

    Items from 198th Technical Meeting - Fall 2020