Improvement in Insulating Property of Polypropylene Film Based on Polar Molecule Doping and Structural Design
Polypropylene(PP)film has the advantages of high breakdown field strength and low dielectric loss,which is the most widely used dielectric material in metallized film capacitors.In order to improve the insulation performance of poly-propylene film under high temperature and strong field,terephthalaldehyde and parylene were selected as additives to prepare three kinds of composite film samples.The conductivity,breakdown field strength and energy storage density at different temperatures were tested.The results showed that the composite film with 0.02%terephthalaldehyde and 0.02%parylene doping in each functional layer exhibited the best performance.The conductivity decreased by 95.3%～98.6%,the breakdown field strength increased by 26.7%～32.1%and the energy storage density increased by 86.9%～89.4%.Based on the density functional theory,the electrostatic potential distribution and band gap of polar molecules were calculated.The results showed that the additives concentrated on both sides of the film could cause the charge trapping effect,promote the generation of re-verse electric field at the interface,thus improving the insulation performance of the polypropylene film.The research results will provide a reference for the interface modification and the selection of polar molecule.
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