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Dynamic Mechanical Analysis of Two Component Epoxy Crosslinking Networks After Solvent Exposure

Authors
  • Shannon, James E
Publication Date
Jun 01, 2022
Source
[email protected]
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Abstract

Epoxies are widely used as binding agents in industries where they may be exposed to a variety of solvents that could affect their crosslinked networks and change their physical properties. Irreversible changes to the cross-link network can be a cause of failure when epoxy-assembled composites are used in the field. Dynamic mechanical analysis (DMA) was used to observe changes in glass transition temperatures (Tg) for two different epoxies. These changes were correlated to the corresponding impact on their crosslinking networks. Samples were exposed to solvents and tested with DMA before and after solvent exposure over two weeks to investigate if changes to the epoxy properties could be determined using the aforementioned method. Water, dichloromethane (DCM), and xylene were selected as solvents and the epoxies were exposed to each solvent for an hour before being removed and allowed to age under ambient conditions. Dichloromethane had the most significant effect on the Tg for both epoxies tested. Boiling water was second followed by both xylene and water at room temperature. It is believed that the polarity, the molecular size, and temperature of each solvent affected its ability to penetrate into and swell or damage the crosslinking networks. Finally, all epoxy and solvent combinations showed some degree of recoverable mechanical properties suggesting mechanical changes were caused by a combination of reversible swelling and irreversible damage to the crosslinked network.

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