Effects of thermal aging on chemical-physical and electrical properties of poly(propylene terephthalate).

Poly(trimethylene terephthalate) (PPT) was subjected to aging at high temps. (150-190°C) in air and some mech. (impact strength), phys. (wt. loss), and elec. (dc cond. and ac elec. strength) properties were detd. as a function of aging time and temp. Some chem.-phys. characteristics (such as the av. mol. wt., the carboxyl end-group content, and crystallinity degree) were investigated during the degrdn. process, as well. From the collected data, the thermal endurance parameters (i.e., the temp. index and the halving interval), which are key parameters in the detn. of material reliability and design of elec. insulating systems, were derived according to IEC 216 Std., and compared with those relevant to other thermoplastic polyesters