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Photo-induced scission and crosslinking in LDPE, LLDPE, and HDPE

Lookup NU author(s): Dr Ian Craig, Emeritus Professor Jim White


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The molecular degradation characteristics of three different polyethylenes were determined by deriving chain scission and crosslinking concentrations from gel permeation chromatography molecular weight distributions obtained after 3 weeks and 6 weeks laboratory ultraviolet exposure. Injection-molded bars (3 mm thick) made from a low-density polyethylene (LDPE), a linear low-density polyethylene (LLDPE), and a high-density polyethylene (HDPE) were used and all showed strong depth variations in degradation. Degradation was rapid near the exposed surfaces but very little change occurred in the bar centers, due to oxygen starvation. The most rapid rises in scission and crosslink concentrations were observed with LDPE, for which the concentrations after 6 weeks exposure were approximately double those measured after 3 weeks. With LLDPE and HDPE the scission and crosslink concentrations after 6 weeks exposure were very much greater than twice those after 3 weeks. Scission dominated over crosslinking at all depths and for all materials the scission/crosslink ratio was always ≥3, with a value of ̃9 recorded for HDPE near the exposed surface after 6 weeks exposure. © 2005 Society of Plastics Engineers.

Publication metadata

Author(s): Craig IH, White JR, Shyichuk AV, Syrotynska I

Publication type: Article

Publication status: Published

Journal: Polymer Engineering and Science

Year: 2005

Volume: 45

Issue: 4

Pages: 579-587

Print publication date: 01/04/2005

ISSN (print): 0032-3888

ISSN (electronic): 1548-2634

Publisher: Wiley-Blackwell


DOI: 10.1002/pen.20313


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