Toughening epoxy resin by constructing π-π interaction between a tung oil-based modifier and epoxy

Abstract

Thermosets of the diglycidyl ether of bisphenol A (DGEBA) are normally brittle owing to its rigid structure. To address this problem, a bioinspired strategy to form sacrificial bonds in a curing system, which may enhance the flexibility of epoxy thermosets and maintain a favorable strength simultaneously has been proposed. A tung (Aleurites montana L.) oil diglyceride based-acid (TODGA) that may construct sacrificial bonds with the epoxy matrix in the form of π-π interactions was prepared, and was added into a DGEBA / polyetheramine curing system at varying ratios. TODGA can greatly improve the flexibility and toughness of epoxy thermosets. At the addition of 7.5 wt%, the elongation at break, toughness, and impact strength are improved from 5.9 % to 86.6 %, from 2.1 to 19.0 MJ m−3, and from 4.3 to 5.9 kJ·m−2 respectively, while the tensile strength is maintained at 34.8 MPa. In comparison, the toughening effect of TODGA outperforms that of commercial epoxidized soybean (Glycine max (L.) Merr.) oil. Although TODGA is a flexible modifier, it does not significantly decrease glass transition temperature and thermal stability. These results demonstrate that fabricating sacrificial bonds is a practical way to toughen epoxy thermosets, and TODGA can be potentially utilized as a commercial toughening agent.