To investigate the effect of electrical-thermal-mechanical multi-field aging on the properties and electrical conductivity characteristics of biaxially oriented polypropylene ( BOPP) films for dry-type DC capacitors

BOPP films with a thickness of 5. 8 μm were subjected to aging treatment under typical work-ing conditions of 150 kV/mm

80 ℃

and 10 N for 360 hours. Physicochemical and electrical properties of the films before and after aging were tested

and conductivity current measurements were conducted at 30

50

70 ℃ and under an electric field range of 60-180 kV/mm. The conductivity characteristics of BOPP films before and after multi-physical field aging were investigated and the conduction mechanisms were clarified. The results show that multi-physical field aging leads to an increase in the volume and number of surface defects

a decrease in molecular weight

and an increase in lamellar thickness and crystallinity. Meanwhile

multi-physical field aging decreases the dielectric constant and DC breakdown field strength

and increases the dielectric loss

leakage current

and trap density. The conduction mech-anisms of BOPP films are dominated by hopping conduction and the Poole-Frenkel effect. For unaged BOPP films at 30℃

the conduction mechanism is hopping conduction in the range of 60-120 kV/mm

which transforms to the Poole-Frenkel effect in 120 -180 kV/mm. After multi-field aging

both the hopping distance of hopping conduction and the threshold electric field for the transition between the two conduction mechanisms decrease gradually. The research results can provide theoretical basis and experi-mental data reference for the performance optimization of BOPP films used in dry-type DC capacitors.