The space charge behavior such as charge distribution and electrical conduction of chemically modified, maleic anhydride (MAH) grafted low density polyethylene (LDPE) was investigated. The effect of Low-molecular -mass-species on the space charge behavior of LDPE was investigated. Also, the space charge distributions in the multilayer laminates and blends of LDPE or modified LDPE with ethylene-vinylacetate copolymer (EVA) were investigated.
The MAH grafted LDPE was prepared by reactive extrusion. The low-molecular-mass-species was removed by direct extraction using p-xylene as solvent. Using mutilayer laminated sheet, space charge distribution and charge behavior at the interface between polymers were investigated. The pulsed electroacoustic (PEA) apparatus was used to measure the space charge distribution in sample.
Heterocharge was developed in LDPE. The heterocharge in LDPE decreased with increasing the content of MAH grafted on LDPE. The residual heterocharge became negligible at MAH content higher than 0.20 wt%. The space charge limited conduction (SCLC) which was a main mechanism for the electrical conduction of LDPE remained unchanged after the chemical modification by MAH grafting reaction. The conduction current and effective charge mobility of MAH grafted LDPE decreased with increasing the content of MAH. These results were attributed to the enhanced homocharge trapping at MAH component acting as trapping sites.
The heterocharge in LDPE decreased with removing the low-molecular-mass-species containing chemical impurities. The SCLC was analyzed to be the main mechanism for the electrical conduction after the removal of low-molecular-mass-species. The conduction current and effective charge mobility at high electric field decreased with removing the low-molecular-mass-species. These results attributed to the decrease of chemical impurities such as carbonyl group and double bonds. Also, the decrease of conduction current and effective charge mobility ...