Influences of annealing method on space charge characteristics of low density polyethylene

In this paper, low density polyethylene (LDPE) film samples were prepared by three kinds of annealing methods which were different in cooling rates. Lower cooling rate results in larger spherulite and higher crystallinity. A pulsed electro-acoustic (PEA) space charge measurement system was improved to solve the surface discharge problems for high voltage and small samples. Negative DC fields from 50 to 220 kV/mm were applied on the samples. The influences of annealing methods on space charge and space charge packet characteristics were measured by the improved PEA system. Mobility and trap depth of released charges were calculated by space charge decay which was measured by PEA method. Average velocity and mobility of space charge packets were calculated by space charge packet dynamics. It's found that the lower rate cooling samples have higher crystallinity, more homo-charge accumulation, lower mobility and deeper trap depth. We presumed there are inherent relationships in existence.