Hydrolytic degradation and thermal properties of epoxy resins derived from soybean oil

Abstract

Vegetable oils are an attractive substitute for petroleum sources for the derivation of polymers. Epoxy resins have been synthesized containing epoxidized soybean oil (ESO) and traditional petroleum-derived epoxy resin components (the diglycidyl ether of bisphenol A [DGEBA] and methylene dianiline). The curing reaction was moni-tored with in situ differential scanning calorimetry, indicating that significantly higher curing temperatures are required for ESO as compared with DGEBA. Increasing the concentration of ESO in the resin sig-nificantly decreased the glass transition temperature. However, epoxy resins with high ESO content (60–100 wt% relative to the total epoxide-bearing molecules in the mixture) exhibited a second, higher-temperature peak in the derivative of the thermogravimetric analysis weight loss curve. Significant differ-ences were observed in the hydrolytic degradation characteristics of the polymers at 80°C in NaOH solutions. Polymers with 0–40 wt% ESO exhibited little measurable mass loss over 72 days (in both 3 and 10 wt% NaOH solutions), while polymers with 60–100 wt% ESO exhibited substantial mass loss within 2 weeks in a 3 wt% NaOH solution. The presence of degradable cleavage points throughout the network structure may provide a valuable route for recycling these materials after their useful lifetime. Supple-mentary information is available at http://www.icevirtuallibrary.com/upload/10.1680gmat.12.00023_SupplementaryInformation.pdf