Hetero and Homocharge in LDPE at Low Electric Fields

Various studies have shown that in Low-Density Polyethylene (LDPE), homocharge (like polarity charge) accumulation is likely in the vicinity of electrodes at low electric fields, whereas heterocharge accumulation (opposite polarity charge) is likely at high electric fields. However, the effect of material morphology on the occurrence of homo/heterocharge is not well established. In this work, LDPE samples from two different types of pellets are prepared using the solvent casting technique. The space charge measurements using the Puled-Electro-Acoustic (PEA) method are carried out at an electric field of 20kV/mm. The space charge measurements show a homocharge formation in one sample and a heterocharge formation in the other. This is intriguing and deserves closer attention. FTIR measurements show no significant differences in the chemical composition of these two samples. DSC measurements indicate a higher degree of crystallinity in the sample exhibiting homocharge. A higher crystallinity lowers the mobility of charge carriers preventing heterocharge formation.