Effects Of The Antioxidant And Degassing In Melt Condition On The Space Charge And Conductivity Of LDPE

Polyethylene, because of its excellent physical properties and electricalinsulating properties, is the first choice of the high-voltage direct currenttransmission cable materials. The impurities from the residues and additive in theprocess of industrial production of polyethylene material, lead to formation chargetraps by the polyethylene material defects in physical and chemical. Under the DCelectric field, the traps may capture carrier then lead space charge accumulation.Generation and accumulation of space charge distort the electric field distribution ofinsulating materials, and thus affect the dielectric properties of the cable material.In this dissertation, we studied the effect of antioxidant and degassing in meltcondition on the space charge distribution and DC conductivity characteristics. Byadding different mass fraction of antioxidant to the two commercial low densitypolyethylene and then blended them. By Fourier Transform Infrared Spectroscopymeasuring, the chemical structure change of the low density polyethylene with andwithout different mass fraction of antioxidant after being degassed in melt conditionwere observed.Through the result of PEA test, the degassing process in melt condition caneffectively reduce the content of impurities, and improve chemical defects ofmaterial, then reduce space charge accumulation. The antioxidants with lowmolecular compound will increase homo-charge injection. The j-E conductivitycharacteristics experiment results showed that degassing process in melt conditioncould reduce impurity ions in LDPE sample, and then reduce the electric currentdensity. Adding antioxidants can effectively suppress the migration of carrier in lowmolecular compound under high electric field, and then reduce the conductivity of LDPE.