Composite materials present an array of design challenges from both a manufacturing and performance perspective. Our work builds on the concept of dynamic heterogeneity, where enhanced toughness has been previously observed for samples with regions of different local glass transition temperatures. The temperature limits for which this approach can be usefully applied has been investigated here, using the model epoxy systems developed previously by Masser et al in their investigations of the role of dynamic heterogeneity. These model systems are based on diglycidyl ether of bisphenol A, crosslinked with either a rigid, cycloaliphatic amine or one of a series of flexible poly(propylene oxide) diamines. Fracture toughness measurements were performed at temperatures well below the glass transitions temperatures of the soft component to understand the limits of the toughness enhancement that can be attributed to dynamic heterogeneity. We also used the same model system to investigate the cure kinetics and the associated time dependence of the tack energy of the epoxy formulations during the cure process. The tack energy and the fracture toughness were both correlated with the time-dependent linear viscoelastic properties measured at a frequency of 15 MHz with quartz crystal resonators. The resonators provide a cheap, quantitative measure of the properties of the epoxy resins throughout the cure process.

Toughness, tack, and high-frequency viscoelastic properties of model epoxies

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.