Modifications of polypropylene surface properties by alpha ionizing radiation

A copolymer of polyethylene-polypropylene (PP/EPR) was irradiated using alp ha particles under three different atmospheres. First, samples were irradia ted by alpha particles (4.3 MeV) in a gas-tight chamber under either dry or moist air. Next, irradiation was carried out under a 4 x 10(-4) Pa vacuum. Pristine and treated sample surfaces were studied by Attenuated Total Refl ectance infrared spectroscopy (FT-IR/ATR). It was possible to ascertain tha t the chemical modifications produced differ according to the atmosphere du ring irradiation. Under vacuum, vinylic bonds were created. In moist air, c arbonyl bonds were formed; and in dry air, both kinds of bonds were produce d. In each case, a decrease in the number of C-H bonds after irradiation wa s noted. As polypropylene is widely used in the automobile industry for par ts like dashboards and bumpers, this study could be useful for many of the industry's applications. Indeed, it has been determined that, along with ch emical modifications generated from the surface of the irradiated copolymer , an increase in its surface free energy results in greater wettability to certain liquids, such as water, formamide and diiodomethane. (C) 2000 Elsev ier Science B.V. All rights reserved.