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 surfaces that have been treated for between 0.7–1 s 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 performed on helium treated High Density Polyethylene (HDPE) in order to point out the structural modifications.
