Breakdown Strength of Polypropylene Films Demetallized by High-Power Surface Discharge

The influence of Al and Zn metallization and demetallization processes on breakdown strength of thin polypropylene film is investigated. The breakdown strength of a polypropylene film drops about 10% upon covering with thermally evaporated 10 to 50 nm thick Al metallization, and it weakly depends on the thickness of metal layer. Al form nanoparticles 10-20 nm in size over polypropylene fibers at the initial stage of metallization layer formation. These nanoparticles grow and coalesce with Al layer thickness increase. The demetallization by the electric explosion and surface arc discharge induced erosion of metal layer (aluminum or zinc) process leads to up to 30% reduction of breakdown strength for aluminum metallization, and up to 20% for zinc metallization, respectively.