Preparation and properties of soybean oil–based curing agents for epoxy resin

In order to improve the flexibility properties of conventional epoxy resin, two novel soybean oil–based curing agents were synthesized. The curing agent obtained from the reaction between epoxy soybean oil and ethylene diamine was named EEDA, and another curing agent derived from epoxy soybean oil and isophorone diamine was named EIPDA. Several techniques were used to systematically investigate the effects of the structure and content of the two curing agents on the properties of the cured products. The Fourier transform infrared analysis demonstrated that epoxy resin reacted with soybean oil–based curing agents. The differential scanning calorimetry analysis showed that the curing process between diglycidyl ether of bisphenol-A (DGEBA) and soybean oil–based curing agents only had an exothermic peak. Thermogravimetric analysis indicated that the cured DGEBA/EIPDA system was more stable than the DGEBA/EEDA system below 300 °C. Mechanical tests and Shore D hardness tests suggested that excessive EEDA greatly enhanced the toughness of cured products because of the introduction of aliphatic chains.© 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44754.