Analysis of chain-scission and crosslinking rates in the photo-oxidation of polystyrene

✍ Scribed by A. V. Shyichuk; J. R. White

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 180 KB
• Volume: 77
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/1097-4628(20000923)77:13<3015::aid-app28>3.0.co;2-w

✦ Synopsis

A study of the chain-scission and crosslinking rates in polystyrene photodegraded in the laboratory with fluorescent tubes (UVA-340) was made using GPC molecular weight distributions. The analysis was based on the assumption that scission and crosslinking occur randomly and employed a Monte Carlo procedure to compute the changes in molecular weight distribution for chosen values of scission and crosslinking rates and compared the computed profiles with measurements made on the photodegraded samples. Results were obtained for three different exposures and at various depths within 3.2-mm-thick bars. The scission/crosslinking ratio, , was between 3 and 8 for all samples measured in this study. The lowest values of were found near the exposed surface and the highest near the bar center. Both scission and crosslinking rates were much lower in the interior, presumably the result of oxygen starvation. Some bars were exposed while loaded to 10 MNm Ϫ2 in uniaxial tension. The stress appeared to increase the reaction rates somewhat near the surface and to depress the rates in the interior correspondingly.