SURFACE MODIFICATION OF A POLYPROPYLENE FILM BY LOW-PRESSURE DISCHARGE AND THE ADHESION OF A VACUUM-DEPOSITED LAYER OF ALUMINUM

Low-pressure discharge treatments were applied to the surface of polypropylene. ESCA analyses, wettability measurements and adhesion tests were carried out to characterize surface modifications as a function of treatment time and nature of gas (air or argon). Advancing and receding contact angles were measured with an automatic dynamical tensiometer. The liquids used were water (very polar liquid) and methylene iodide (apolar liquid). The results show an increase in wettability by the surface treatment. This is due to the creation of high-energy polar sites. ESCA analysis also shows that the modified surface layer is soluble in methanol and is made up of low-molecular-weight material. Adhesion of polypropylene/aluminium is also increased by the low pressure discharge treatment from the few first seconds of the treatment. This adhesion increase is a function of the polar component of the polymer surface energy.