Liquid Crystalline Copolyesters as High Temperature Adhesives for Aluminum

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Abstract
A liquid crystalline copolyester consisting of 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, with a composition (73:27) was studied as a melt processible, high temperature adhesive. The polymer was used as received without any additional treatment and was applied on an aluminum substrate as a film. The adhesive joints were prepared using different processing conditions and good bonding between the two polymer surfaces was observed under most of these conditions. The reliability of the adhesive bond was estimated by measuring the lap shear strength (1.4-1.6Ksi) and the crack propagation in the wedge test. Improved adhesion (2 times) over epoxy adhesives, applied on the same substrate, was observed when tested at room temperature and there was no significant decrease in the lap shear strength in the range RT-180[ddot]C. The post-failure surfaces were studied with SEM and it was observed that separation occurred within the adhesive.