Pulse and continuous ion beam treatment of polyethylene

Abstract

Polyethylene (PE) films were treated by a nitrogen ion beam with an energy of 20 keV at a quasicontinuous regime with low current density and at a pulse-periodical regime with high current density. IR ATR spectra and UV spectra showed significant differences in structural changes of PE treated by pulse and continuous treatment at the same average current density. The changes in the molecular structure that are induced by ion beams, i.e. the appearance of aromatic cycles, unsaturated bonds and carbonyl groups in PE, have a similar qualitative character for all types of ion beam regimes. However, the same degree of structural changes is achieved at lower dose in the pulse regime than in the continuous regime. At equal treatment parameters (ion energy, dose treatment, average current density) the pulse regime leads to a higher concentration of unsaturated and oxygen-containing groups then the continuous regime. This effect at the pulse regime can be explained by the high current density in the single pulse, at which a high local temperature is generated in the ion track field of the polymer. Probably this leads to a wave of internal stress, and these effects additionally stimulate structural changes in the polymer at pulsed ion beam treatment.