Partially reacted substructures method for thermoset epoxies studied using molecular dynamics simulations

C. Jang, M. Sharifi, G. R. Palmese, C. F. Abrams

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We employed the "partially reacted substructure (PRS)" method to enhance the material properties of the diglycidyl ether of bisphenol A (DGEBA) epoxy thermosets. This method involves first partially curing DGEBA with a small amount of poly(oxypropylene)diamine (POPDA) and then adding DGEBA and diethyltoluenediamine (DETDA) to continue to a fully cured sample. PRS-induced DGEBA-DETDA/POPDA 2:1 epoxy-amine stoichiometric samples have consistently higher Tg's and glassy state densities than samples created using one-step cure of a blend of DGEBA with both DETDA and POPDA. PRS-induced samples were found to be twice as tough as non-PRS samples. Because the compositions are identical, differences observed must arise from differences in the network isomers formed by the two curing protocols and the resulting differences in packing and intermolecular interactions. Molecular dynamics (MD) simulations were carried out to better understand these phenomena. The density and glass transition temperature in the simulations are in quantitative agreement with the experimental results. One reason for this Tg increase in PRS-induced samples may be related to the pendant methyl groups on POPDA, as illustrated using radial distribution functions (RDF's) computed from the MD simulation trajectories. Methyl-methyl RDF's for non-PRS samples did not differ significantly from those of the prepolymerized liquid, but the methyl-methyl RDF's for the PRS-samples showed stronger methyl-methyl correlation at all distances, signifying better intra- and intermolecular POPDA packing. This results in lower POP backbone flexibility in the PRS samples and consequently higher Tg's relative to the non-PRS samples. Further simulations aim to ultimately focus on the ductility enhancement conferred by PRS.

Original languageEnglish (US)
Title of host publicationProceedings of the American Society for Composites - 30th Technical Conference, ACS 2015
EditorsXinran Xiao, Dahsin Liu, Alfred Loos
PublisherDEStech Publications
ISBN (Electronic)9781605952253
StatePublished - 2015
Externally publishedYes
Event30th Annual Technical Conference of the American Society for Composites, ASC 2015 - East Lansing, United States
Duration: Sep 28 2015Sep 30 2015

Publication series

NameProceedings of the American Society for Composites - 30th Technical Conference, ACS 2015

Other

Other30th Annual Technical Conference of the American Society for Composites, ASC 2015
Country/TerritoryUnited States
CityEast Lansing
Period9/28/159/30/15

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites

Fingerprint

Dive into the research topics of 'Partially reacted substructures method for thermoset epoxies studied using molecular dynamics simulations'. Together they form a unique fingerprint.

Cite this