Surface morphology of polyethylene after treatment in a corona discharge

Abstract

Corona treatment of low‐density polyethylene in oxygen or oxygen‐containing gases produced bumps on the surface, while treatment in nitrogen, hydrogen, argon, or helium caused no detectable surface change. Bumps made by an oxygen corona increased in size with time and temperature of the treatment. The bumps were removed when a treated polymer sheet was dipped into solvents such as CCl₄, ethanol, or 0.2% aqueous NaOH. Infrared analysis indicated that most of the oxidized layer was eliminated from the polymer surface by solvent dipping and that the degraded products contained a substantial proportion of CH₂ groups. It is suggested that the bumps are caused by the migration of low molecular weight degradation products to charged areas of the polymer surface.