Polypropylene Films in a Direct-Current Discharge

The effect of dc discharge treatment on polypropylene films—both commercial and stabilizer- and plasticizer-free as prepared under laboratory conditions (with the rac-Et(Ind)₂ZrCl₂–methylaluminoxane catalytic system)—was studied. The discharge treatment was shown to hydrophilize the polypropylene surface in both cases. Negative charged states were detected on the modified surface and their relation to the polypropylene hydrophilization was established. By the thermostimulated relaxation and depolarization techniques, it was shown that the observed charges are induced by injection of plasma electrons into the polymer. It was found that severe changes took place throughout the bulk of the polypropylene film synthesized over the metallocene catalyst, as indicated by enhancement of its crystallinity and a change in the molecular mass distribution.