Room Temperature Curing Resin Systems for Graphite/Epoxy Composite Repair.

Abstract
Adhesive formulations were developed for the repair of damaged graphite/eposy structures on board ship. These adhesives cure at 24C (75F) or in the moderate temperature range of 67 to 121C (150 to 250F). The formulations which gave the best results in lap shear testing were formulated from high molecular weight and high functionality epoxy resins and a polyamine curing agent. A typical formulation is composed of a cresol novalac epoxy, (Ciba-Geigy ECN 1299), the triglycidyl ether of p-aminophenol, (Ciba-Geigy 0510), and diethylenetriamine, a polyamine curing agent. After a 72 hour cure at 24C (75F) an adhesive compounded from this formulation had much higher lap shear strength at 121C (250F) than did commercially available epoxy, acrylic, and anaerobic adhesives. Aluminum/aluminum bonds tested in a rapid heat-up to 121C (250F) (at 150F/min) and immediate application of load at 121C (250F) had lap shear strength of 1400 psi whereas the commercial adhesives had 500-700 psi strength in the same test. The formulation when cured at 121C (250F) had lap shear strength at 121C (250F) of 2700 psi. Another promising system is the vinyl ester resin system as a moderate temperature, 66C to 121C (150F to 250F), curing adhesive. It has good environmental durability. and methodological research. (Author)

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