Research On Interface Modification And Space Charge Behavior Of Nano MMT/PE Composites

The space charge problem of polymer insulation high voltage direct currentcable has attracted more and more attention at home and abroad. The generationand accumulation of space charge was inhibited by various methods to reduce theinsulation deterioration caused by space charge effects. Adding nano particlesinto polymer insulation could improve its original performance, meanwhile it is avery effective method to inhibit the space charge.The formation mechanism of interface as the core elements, composites withdifferent interfaces are prepared and tested. Two organic processing methods areselected to nano-montmorillonite (MMT) particles; one is using intercalationagent independently (O-MMT), the other is using intercalation agent andcoupling agent in union (S-O-MMT). Nano montmorillonite/polyethylene(MMT/PE) composites with three different interfaces are prepared via meltingintercalation method while low density polyethylene (LDPE) is as polymermatrix and maleic anhydride grafted polyethylene is as compatilizer (C).Space charge distribution of composites was measured via Pulsed Electro-Acoustic (PEA) method, and the space charge behavior which is under electricfield or short circuit condition of dielectrics with different interface is researched.In addition, basic properties of dielectrics are tested, including conductivity,dielectric spectrum and mechanical property. Compared to PE, the space chargeunder the electric field in the samples of O-MMT/PE composites is reduced, butheterocharge is discovered near the electrodes; releasing speed of charge undershort circuit is lower. Conductivity of composites is lower than PE either underhigh or low field strength. The dispersing and bonding strength of interface in S-O-MMT/PE and O-MMT/C/PE composites are better than O-MMT/PE, theheterocharge near the electrodes is almost disappeared. Space charge releasingbecomes more difficult and conductivity becomes lower under high field strength. Periods of time which the stabilization of space charge distribution in compositesneeds is less than PE; in addition, the phenomenon of electrical field distortion isgreatly improved. The permittivity of composites is lower than PE, but the testresult of dielectric loss tangent is just opposite. Compared to PE, although themechanical property of the whole composites is declined, but S-O-MMT/PE andO-MMT/C/PE system is better than O-MMT/PE system.