Bridging Strength and Ductility in Crosslinked Epoxy Networks AITranslate

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DOI：https://doi.org/10.1021/acsapm.3c00586

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By introducing a monofunctional epoxy compound in epoxy-amine structural adhesives, a series of polymer glasses are studied which systematically varies the apparent molecular weight between crosslinks (Mc,a) from 500 to 1800 g/mol while maintaining a glass transition temperature (Tg) above 110 °C. Young’s modulus and yield strength, measured in uniaxial tension, increased with increasing Mc,a breaking from common trends in highly crosslinked polymers. Positron annihilation spectroscopy elucidated a local densification of the relative free volume with increasing monofunctional epoxy content, providing a plausible origin to the increase in tensile properties. While fracture toughness (KIC) remained relatively constant across the series, the high-rate impact performance increased as a function of tensile strength achieving a 10% improvement in impact resistance. Overall, this study highlights the sensitivity of macroscale, mechanical performance on polymer topology, and local density within the polymer glass.