Partial discharge degradation of several biodegradable polymers

Partial discharge (PD) resistance was examined by applying a constant voltage to four different biodegradable polymers-poly-L-lactic acid (PLLA), polyethylene terephthalate succinate (PETS), poly ε-caprolactone butylene succinate (PCL-BS), and polybutylene succinate (PBS)-and the results were compared with those of low-density polyethylene (LDPE) and crosslinked low-density polyethylene (XLPE). The PD resistance is determined by the erosion depth and the surface roughness caused by PDs, and is ranked as LDPE ≈?XLPE > PLLA ≈?PETS > PBS > PCL-BS. This means that the sample with a lower permittivity has better PD resistance. Furthermore, examination of the sample surfaces by a polarization microscope and a laser confocal microscope reveals that the PD resistance of crystalline regions with spherulites is higher than that of amorphous regions. Therefore, good PD resistance can be achieved by the sample with a high crystallinity and a low permittivity.