The Photo-Oxidation of Polypropylene Monofilaments

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Abstract
The photo-oxidation of commercial, isotactic polypropylene monofilament, initiated by xenon-arc irradiation in air, leads to the initial accumulation in the fiber surface of both carbonyl species and hydroperoxide groups. These chemical changes are accompanied by a severe drop in the elongation at break. Extended irradiation leads to a substantial accumulation of these oxidation products throughout the fiber and to a loss of tensile strength. Oxidation products were identified and estimated from transmission and internal reflection in spectroscopy [∼C(O)∼ and —OH] and by chemical analysis (—OOH). Marked increases in fiber wettability were also found to accompany photo-oxidation. Distinct differences in product ratios from photo-oxidized polypropylene film and fiber samples were observed. These differences are consistent with the morphological control of the efficiency of initiation after hydroperoxide photocleavage, but are more likely to result from some radical scavenging by the unextractable phenolic additive in the commercial fiber.