An analytical approach toward monitoring degradation in engineering thermoplastic materials used for electrical applications

Engineering thermoplastics are being used in a broad array of applications throughout the electrical industry. Polyester thermoplastics offer desirable electrical and mechanical properties; but when used in the wrong environments, they can be susceptible to hydrolysis. Size exclusion chromatography (SEC) can be used as an analytical tool for monitoring the degree of hydrolytic degradation occurring to engineering thermoplastic materials. By characterizing the molecular weight distribution of a polymer, a direct method of assessing the mechanical performance of the material can be obtained. Three polyester materials, i.e., PBT, PET and PCT, along with two polyphthalamide materials (PPA) were environmentally degraded at a temperature of 60°C and a relative humidity level of 100%. The changes in molecular weight distribution with respect to time are monitored and related to the tensile strength values for the materials. The results reveal that the PET and PET materials are the most susceptible to hydrolytic degradation. The PPA materials proved to be quite resistent to hydrolytic degradation. Also, the two PPA materials were found to be quite different in terms of their molecular weight distributions and tensile strength characteristics