STRESS DEVELOPMENT IN POLYMER COATINGS DURING THERMAL CYCLING - A BENDING - BEAM APPROACH.

A simple and in-situ bending-beam technique was used to investigate the stress-temperature relationship during thermal cycling of two polymer films, poly(methyl methacrylate) and an amide-imide polymer, on fused quartz beams. Using this technique, stress relaxation near the polymer's glass transition and relaxation caused by cracking of the polymer can be detected. From the Poisson's ratio and Young's modulus for poly(methyl methacrylate), the thermal expansion coefficient (7. 18 multiplied by 10** minus **5 / degree C) calculated from the linear stress-temperature relationship is in good agreement with previously published values.