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Unexpected Thermomechanical Behavior of Off-Stoichiometry Epoxy/Amine Materials

Recent studies on off-stoichiometric thermosets reveal unique viscoelastic behavior derived from increased free volume and physical interactions between chain ends. To understand structural characteristics arising from cure and its effect on properties, we developed a Monte Carlo model based on step...

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Bibliographic Details
Published in:Macromolecules 2023-04, Vol.56 (8), p.3183-3194
Main Authors: Foster, Jeffrey C., Yoon, Alana, Lyons, Kenneth, Martinez, Estevan J., Leguizamon, Samuel C., Bezik, Cody T., Frischknecht, Amalie L., Redline, Erica M.
Format: Article
Language:English
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Summary:Recent studies on off-stoichiometric thermosets reveal unique viscoelastic behavior derived from increased free volume and physical interactions between chain ends. To understand structural characteristics arising from cure and its effect on properties, we developed a Monte Carlo model based on step-growth polymerization. Our model accurately predicted structure–property trends for a two-component system of EPON 828 (EPON) and ethylenediamine. A second epoxy monomer, D.E.R. 732 (DER), was investigated to modulate T g. Binary mixtures of EPON and DER in off-stoichiometric, amine-rich formulations resulted in nonlinear evolution of thermomechanical properties with respect to initial formulation stoichiometry. Modifying our model with kinetic parameters allowing for differential epoxide/amine reaction kinetics only partially accounted for trends in T g, suggesting that spatiotemporal contributionsnot captured by our modelwere significant determinants of material properties compared to polymer architecture for three-component systems. These findings underpin the importance of spatial awareness in modeling to inform the development of dynamic thermosets.
ISSN:0024-9297
1520-5835
DOI:10.1021/acs.macromol.2c02414