ABSTRACT
STUDY OF HE-NH 3 PLASMA MIXTURES AND THEIR ROLE IN THE STABILITY OF THE PLASM A TREATED POLYPROPYLENE SURFACE
J. K U R D I, F. A R EFI-K H O N SA R I, M. TA TO U LIA N and J. A M O U R O U X
Laboratoire de Genie des Precedes Plasmas, Universite Paris VI, ENSCP 1 1 , rue Pierre et Marie Curie, 75231 Paris cedex 05, France
The purpose of this work was to minimize the well-known ageing phenomenon of the plasma-treated polymer surfaces, by stabilizing the outermost layer via crosslinking using discharges in mixtures of ammonia (reactive gas) and helium (noble gas). Treatments in He + NH3 gas mixtures are interesting because they produce a surface nitridation simultaneously with a crosslinking reaction in a one step process. The physicochemical modifications of He+NH3 treated polypropylene have been studied in terms of the wettability, the acid-base and the mechanical properties. The contact angle measurements reveal that for He-rich mixtures (>96% He), there is an optimum in the stability of the surface wettability with a basic character comparable to the one obtained for pure ammonia plasma. Similarly, stress-strain characteristics show that mixtures with a high percentage of helium (>96%) enhance the cohesive strengthening of the polymer surface by the formation of a thin crosslinked layer that mechanically stabilizes the surface. Such treated surfaces with a predominant basic character and stable surface properties are very useful for applications such as metallization of polymers.
