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Lookup NU author(s): Emeritus Professor Jim White
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Chain scission and crosslinking rates have been derived from molecular mass distributions obtained by gel permeation chromatography at different stages during photodegradation of polypropylene samples exposed to ultraviolet irradiation (UV). Results for rubber-toughened polypropylene (PP) containing no photostabilizer are compared with those for the same polymer stabilized using a commercial photostabilizing package (PPS). The samples were in the form of 3 mm thick bars and measurements were obtained at various depths from the exposed surface after different exposure times. The depth profiles for PP and PPS were very different. Reaction rates in the interior of PP showed oxygen diffusion limited behaviour and after prolonged exposure, the rates in the interior of PPS were higher than those in PP. The ratio of scission rate/crosslink rate fell when reaction rate increased. Crosslinking became relatively more likely when reaction rates were low. The low degradation rates obtained with stabilized polymer coupled with the sensitivity of the method of analysis enabled detection of inhibition of photodegradation attributed to residual moulding stresses in the samples. © 2007 Elsevier Ltd. All rights reserved.
Author(s): White JR, Shyichuk AV
Publication type: Article
Publication status: Published
Journal: Polymer Degradation and Stability
Print publication date: 01/11/2007
ISSN (print): 0141-3910
ISSN (electronic): 1873-2321
Publisher: Elsevier Ltd
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