SURFACE AND BULK ANALYSES OF THE OXIDATION OF POLYOLEFINS

The non-uniformity of oxidation across polypropylene and polyethylene films has been measured by a combination of X-ray photoelectron spectr oscopy (XPS), internal reflection infrared spectroscopy and bulk prope rty measurements. Films were photo-oxidized or gamma-irradiated in air . Photo-oxidized film showed detectable oxidation at a very early stag e in the outermost 70 Angstrom of the film thickness (as measured by X PS). Oxidation advanced into the films as exposure level increased. Al though gamma-irradiated films also showed enhanced surface oxidation, this was attributed to the reaction of the polymer surfaces with short -lived species such as ozone from the radiolysis of the moist air atmo sphere. When films were gamma-irradiated and oxidized under conditions which precluded these reactions, oxidation proceeded uniformly throug hout the film cross-section.