Nature of adhesive bonding via interchain transesterification reactions (ITR)

Secondary ion mass spectrometry (SIMS) was used to determine the nature of the adhesive bonding which occurs through interchain transesterification (ITR) in thermosetting polyester materials (TS) and in liquid crystalline polyester polymers (LCP). An all aromatic copolyester thermoset was prepared as a deuterated and undeuterated film. These films were cured and then consolidated using heat and pressure to form a good adhesive bond. SIMS produced no direct observation of interdiffusion indicating that the length scale over which it occurred must be less than 500 Angstrom (the resolution of the technique). A similar set of experiments was carried out using a deuterated and non-deuterated film of a liquid crystalline copolyester (LCP) consisting of 73/27 p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. In this case, the deuterated units diffused throughout the entire undeuterated films within less than one hour at 280 degrees C.