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Macromolecular scission and crosslinking rate changes during polyolefin photo-oxidation

Lookup NU author(s): Emeritus Professor Jim White

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Abstract

Chain scission and crosslinking rates have been derived from molecular mass distributions obtained by gel permeation chromatography at different stages during photodegradation of various thermoplastics exposed to ultraviolet irradiation (UV). Results are given for a high density polyethylene (HDPE); a low density polyethylene (LDPE); a linear low density polyethylene (LLDPE); a polypropylene homopolymer (PPHO); and a polypropylene copolymer (PPCO). As the oxidation progressed, it was observed that the scission rate for HDPE, LLDPE, PPHO and PPCO increased near to the exposed surface whereas for LDPE the rate remained almost unchanged. The crosslink rate fell near to the surface with HDPE and LDPE but increased with PPHO and PPCO. The reaction rates near to the bar centre (∼1.5 mm from the exposed surface) were low for HDPE, PPHO and PPCO; this is attributed to oxygen starvation, caused by consumption of oxygen by rapid reaction near the surface. Reaction was observed in the interior with LDPE and LLDPE, presumably because of a combination of a higher oxygen diffusion rate than for HDPE and a lower rate of consumption of oxygen near the surface than with the polypropylenes. © 2007 Elsevier Ltd. All rights reserved.


Publication metadata

Author(s): White JR, Shyichuk AV

Publication type: Article

Publication status: Published

Journal: Polymer Degradation and Stability

Year: 2007

Volume: 92

Issue: 7

Pages: 1161-1168

ISSN (print): 0141-3910

ISSN (electronic): 1873-2321

Publisher: Elsevier Ltd

URL: http://dx.doi.org/10.1016/j.polymdegradstab.2007.04.011

DOI: 10.1016/j.polymdegradstab.2007.04.011


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