Degradation of polymer coating systems studied by positron annihilation spectroscopy. IV. Oxygen effect of UV irradiation

Citation
R. Zhang et al., Degradation of polymer coating systems studied by positron annihilation spectroscopy. IV. Oxygen effect of UV irradiation, J POL SC PP, 39(17), 2001, pp. 2035-2047
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS
ISSN journal
0887-6266 → ACNP
Volume
39
Issue
17
Year of publication
2001
Pages
2035 - 2047
Database
ISI
SICI code
0887-6266(20010901)39:17<2035:DOPCSS>2.0.ZU;2-K
Abstract
The effect of oxygen on the photodegradation of a polyurethane coating indu ced by accelerated UV irradiation was studied with two different light sour ces: 313-nm UVB and Xe lamps. Doppler-broadened energy spectra (DBES) and p ositron annihilation lifetimes were measured. as a function of incident pos itron energy (0-30 keV) and irradiation time (0-100 h). The photodegradatio n of the coating was characterized in terms of subnanometer defect changes. Significant variations of the S parameter (a defect parameter from DBES) a nd the ortho-positronium lifetime and intensity were observed as a function of oxygen concentration during exposure to UV irradiation. These results s howed a significant enhancement in photodegradation due to the presence of oxygen, as indicated by a decrease in free volume and holes at the atomic l evel. Enhanced degradation in the presence of oxygen, as indicated by incre ased free-radical production (observed with electron spin resonance spectro scopy), was also observed. (C) 2001 John Wiley & Sons, Inc.