Understanding Free Volume Characteristics of Ethylene-Propylene-Diene Monomer (EPDM) through Molecular Dynamics Simulations

Abstract

Understanding the underlying processes associated with the viscoelasticity performance of ethylene-propylene-diene monomer (EPDM) during its service life is essential for assessing and predicting its waterproofing performance in underground infrastructure. The viscoelasticity of the polymer is closely related to its free volume, and both of these properties depend on multiple factors, such as temperature, stress magnitude, and strain level. To explore the fundamental viscoelastic behavior of EPDM using free volume as a proxy for viscoelasticity, this article investigates the influence of temperature, stress magnitude, and strain level, as well as their combined effect, on the free volume through molecular dynamics (MD) simulations. An EPDM cross-linked molecular model was built and verified by comparing the simulation values of glass transition temperature, mechanical properties, and gas diffusivity with the experimental results reported in the literature. Then, the dependence of EPDM’s fractional free volume on temperature, strain, and their combined effect was investigated via MD simulations, on the basis of which the applicability of various superposition principles was also evaluated.

Gas permeation and microstructure of reduced graphene oxide/polyethyleneimine multilayer films createdviarecast and layer-by-layer deposition processes

“…The free volume theory posits that gas molecules in polymers can migrate only when surrounded by large enough free volume holes. [68][69][70][71][72][73][74][75][76][77][78][79] Thus, it is of primary importance to analyze the gas permeation within the free volume in PEI/RGO composite lms. Aer all other measurements had been completed, the PEI/RGO composite lms were carefully scraped off the substrate, and the resulting powder-like PEI/RGO composites were mechanically pressed to discs for PALS measurement.…”

“…84 As the free volume theory makes clear, the permeability of gas molecules in polymers is sensitive to the size, density, and distribution of free volumes, as well as the fraction free volume. [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] Moreover, the size, solubility, and weight of the gas molecules also have a signicant inuence on their permeation. [44][45][46] Thus, gas permeation in polymer is a very complex phenomenon, and there is rarely a simple linear relation between the gas permeability and a given parameter.…”

Role of polymer‐filler interaction on Mg(OH)2 and alumina trihydrate‐loaded ethylene propylene diene monomer based polymer composite for high voltage insulation application

“…32 Whereas, 10% activity is shown by hydrogen atom from allyl molecule in ENB which results in crosslinking with main chain aliphatic structure. 33,34 Based on the above explanation we adopted the same mechanism in this article. Coupling agent plays a vital role between filler and polymer to improve interaction by forming covalent bond between the filler and coupling agent molecules.…”

Effect of thermo-oxidation on the dynamical and physical properties of ethylene-propylene-diene monomer elastomer

“…Through MD simulations, Wang et al (2018) studied the effects of carbonyl, scissions, and crosslinks on the microscopic and macroscopic properties of EPDM. Wang YJ et al (2019) revealed free volume characteristics related to the viscosity of EPDM and its dependence on temperature, stress, and strain by MD simulations.…”