Epoxy–imide resins from N‐(4‐ and 3‐carboxyphenyl)trimellitimides. I. Adhesive and thermal properties

Abstract

Epoxy–imide resins were obtained by curing Araldite GY 250 (diglycidyl ether of bisphenol-A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac–epoxy resin; polyfunctional) with N-(4- and 3-carboxyphenyl)trimellitimides derived from 4- and 3-aminobenzoic acids and trimellitic anhydride. The adhesive lap shear strength of epoxy–imide systems at room temperature and at 100, 125, and 150°C was determined on stainless-steel substrates. Araldite GY 250-based systems give a room-temperature adhesive lap shear strength of about 23 MPa and 49–56% of the room-temperature adhesive strength is retained at 150°C. Araldite EPN 1138-based systems give a room-temperature adhesive lap shear strength of 16–19 MPa and 100% retention of room-temperature adhesive strength is observed at 150°C. Glass transition temperatures of the Araldite GY 250-based systems are in the range of 132–139°C and those of the Araldite EPN 1138-based systems are in the range of 158–170°C. All these systems are thermally stable up to 360°C. The char residues of Araldite GY 250- and Araldite EPN 1138-based systems are in the range of 22–26% and 41–42% at 900°C, respectively. Araldite EPN 1138-based systems show a higher retention of adhesive strength at 150°C and have higher thermal stability and Tg when compared to Araldite GY 250-based systems. This has been attributed to the high crosslinking possible with Araldite EPN 1138-based systems arising due to the polyfunctional nature of Araldite EPN 1138. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1729–1736, 2000