Adhesion, wettability and mechanical properties of ammonia - and helium - plasma - treated polypropylene

Abstract

The physicochemical modifications of ammonia-treated polypropylene (PP) films have been studied and characterized in terms of acid-base properties using the contact angle titration method and X-ray photoelectron spectroscopy in conjunction with a molecular probe technique using chloroform as a reference lewis acid. These techniques have shown that PP that have been treated for between 0.7 - 1 are basic in character. For longer treatment times, the basic character of the surfaces decreases, as shown by the above techniques and confirmed by time of flight - secondary ion mass spectroscopy (tof - SIMS). On the other hand, for such treatment times, a degradation of the adhesion and mechanical properties was observed. The ageing of an ammonia-plasma-treated PP was limited by a helium (He) plasma pretreatment known to crosslink the surface, stabilizing in this way the wettability, adhesion and mechanical properties. Tof-SIMS was perdormed on helium treated high Density Polyethylene (HDPE) in order to point out the structural modifications