Modifications of polypropylene surface properties by alpha ionizing radiation

Abstract

A copolymer of polyethylene–polypropylene (PP/EPR) was irradiated using alpha particles under three different atmospheres. First, samples were irradiated by alpha particles (4.3 MeV) in a gas-tight chamber under either dry or moist air. Next, irradiation was carried out under a 4×10 −4 Pa vacuum. Pristine and treated sample surfaces were studied by Attenuated Total Reflectance infrared spectroscopy (FT-IR/ATR). It was possible to ascertain that the chemical modifications produced differ according to the atmosphere during irradiation. Under vacuum, vinylic bonds were created. In moist air, carbonyl bonds were formed; and in dry air, both kinds of bonds were produced. In each case, a decrease in the number of CH bonds after irradiation was noted. As polypropylene is widely used in the automobile industry for parts like dashboards and bumpers, this study could be useful for many of the industry's applications. Indeed, it has been determined that, along with chemical 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.