A precision ultrasonic measurement system has been developed in our laboratory, which allows us to monitor the in-situ bulk and/or surface properties of elastomers, plastics and their composites. The system consists of a pulse-echo unit and an impedance measurement unit.

Polymers are frequently used as adhesives. The strength of an adhesive joint is very sensitive to the in-situ properties of the adhesive in the thin film. For example, a tiny amount of trapped air will have tremendous effect on the stiffness and the practical joint strength. Longitudinal and shear ultrasonic waves could be used to characterize the adhesive properties and quantify the amount of air in the adhesive layer. In this presentation we will show what ultrasonic could tell us about the thin film of air, air/water, water and epoxy between two glass slides or blocks. The ultrasonic signature is so sensitive yet so reliable that if it is processed properly could serve as a sensitive thermometer!