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.


For older papers not listed here, please send your request, including Meeting Year, Title, Author, and Paper # to: cbrady@rubber.org


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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