Degradation of low-density polyethylene and cross-linked polyethylene by partial discharge

To study the degradation of low-density polyethylene (LDPE) and cross-linked polyethylene (XLPE) by partial discharge (PD), experiments were conducted in a nitrogen (N₂) and (N₂+O₂) gas atmosphere. After being subjected to the PD, samples were examined using atomic force microscopy (AFM) and FTIR. The AFM images clearly revealed the creation of pits on the surface of degraded samples. A large difference in the pit pattern was observed between samples subjected to the PD in N₂ and those subjected to the PD in (N₂+O₂). The FTIR spectra detected in samples subjected to the PD in (N₂+O₂) showed that carbonyl compounds were produced on the surface of degraded LDPE. Experiments were performed using an experimental system incorporating GC-MS to measure the gas components produced during degradation. Results of experiments showed that carbon dioxide (CO₂) is produced when LDPE and XLPE are subjected to the PD in an oxygen-containing atmosphere. The amount of CO₂ was found to increase concomitantly with the period of voltage application and oxygen concentration in the area where PD occurs. Based on experimental results, the processes of LDPE and XLPE degradation by PD were examined along with the antioxidant effect on degradation.