The Research On The Effect Of Preparation Process Of Polyethylene On Its Electrical Performance

Polyethylene is widely used in industry, agriculture, medical devices,military products and space supplies, because the molecular structure ofpolyethylene is symmetrical and does not contain the polar groups and has thegood mechanical properties and processing properties, especially polyethylenehas good electrical insulation, therefore it is widely used in wires and cables,converters, motors and power equipments and is used as the reliability materialsof isolation high voltage. Therefore, the electrical properties of the polymermaterials is crucial. All the time,the scholars had researched the conductivity,thedegradation of partial discharge,the breakdown and dielectric properties ofpolymer materials in different voltage and different temperature range and haddraw many scientific research and published many papers. But experiment datasin published papers cannot be very good agreement.As the rapid development of the electrical industry,power technology andelectronic industry,the polyethylene film is prepared on better technology.Cooling is crucial step during the preparation of polyethylene film. The differentof cooling process will lead to the different of the internal microstructure andinfluence its electrical performance such as space chargecharacters,current-voltage characters and the dielectric properties.The plate vulcanizing press is used in this paper.The samples ofpolyethylene film were prepared on three different cooling condition. Thecrystallization of samples was analysed by differential scanning calorimetry.Through the following three test methods,it was analyzed that the differentpreparation way of polyethylene film had a big influence on its electricalproperties.1.Three kinds of samples were observed by space charge measurement system.The experimental results were shown as follow(1) the space chargedistribution of rapid cooling sample fluctuated up and down. This may be thatsmall spherulite scattered uneven in the crystallization.(2) under the10kV/mmand40kV/mm field,the cathode of rapid cooling sample both gathered differentpolarity charge,but under the10kV/mm field,the cathode of medium speedcooling sample and slow cooling sample gathered polarity charge. Rapid coolingsamples are more likely to have different polarity charge.(3) through the shortcircuit space charge,it is known that the decay rate is medium coolingsample>slow cooling sample>rapid cooling sample.(4) through the space chargedistribution data of samples after30min in40kV/mm filed,it is known that thespace charge of the slow cooling sample is least.2.The current-voltage characters curves of three different samples were drew.The experimental results were shown as follow (1)it is known that the resistivityis fast cooling sample>medium cooling sample>slow cooling sample.(2)spacecharge restricted current threshold is slow cooling sample>medium coolingsample> fast cooling sample.3.The dielectric properties of three different samples were tested by thedielectric spectrometer.The experimental results were shown as follow(1)Therelative dielectric constant is fast cooling sample> slow cooling sample>medium cooling sample.(2)The loss factor is medium cooling sample> slowcooling sample> fast cooling sample.