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

Epoxy-imide resins were obtained by curing Araldite GY 250 (diglycidyl ethe r of bisphenol-A and epichlorohydrin; difunctional) and Araldite EPN 1138 ( Novolac-epoxy resin; polyfunctional) with N-(4- and 3-carboxyphenyl)trimell itimides derived from 4- and 3-aminobenzoic acids and trimellitic anhydride . The adhesive lap shear strength of epoxy-imide systems at room temperatur e and at 100, 125, and 150 degrees C was determined on stainless-steel subs trates. 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 degrees C. Araldite EPN 1138-based systems give a room-temperature adhesive lap shear strength of 16-19 MPa and 100% reten tion of room-temperature adhesive strength is observed at 150 degrees C. Gl ass transition temperatures of the Araldite GY 250-based systems are in the range of 132-139 degrees C and those of the Araldite EPN 1138-based system s are in the range of 158-170 degrees C. All these systems are thermally st able up to 360 degrees C. The char residues of Araldite GY 250- and Araldit e EPN 1138-based systems are in the range of 22-26% and 41-42% at 900 degre es C, respectively. Araldite EPN 1138-based systems show a higher retention of adhesive strength at 150 degrees C and have higher thermal stability an d T(g)when compared to Araldite GY 250-based systems. This has been attribu ted to the high crosslinking possible with Araldite EPN 1138-based systems arising due to the polyfunctional nature of Araldite EPN 1138. (C) 2000 Joh n Wiley & Sons, Inc.