Photodegradation of High Polymers. Part 6. Photolysis of Polystyrene Films in Vacuum and in Air
Abstract
Thin films of polystyrene have been photolyzed by 2537A radiation in vacuum and in air at 25 degree, 80 degree, and 120 degree C. Random scission and crosslinking occur simultaneously, with oxygen acting to inhibit the latter process. In air, the apparent quantum yields for random scission, measured by viscosity changes, are 0.00009 and 0.0007 scissions per quantum absorbed at 25 and 120C, respectively. Crosslinks exceed scissions in vacuum, and no reduction in viscosity is observed; the ratio of crosslinks to scissions increases with temperature in the 25 degree to 120 degree C range. During photolysis, hydrogen appears to be the major volatile product emanating from the polymer itself. Of the remaining volatile products, carbon monoxide, carbon dioxide, and methane probably arise from polymer imperfections; benzene and monomer are present as impurities rather than major photolysis products. Large variations in the product yields, which are very small on an absolute scale, and the detection of ethylene from one batch and acetylene from another emphasize the importance of small impurities and imperfections in the photolysis of a highly stable polymer such as polystyrene. Changes in the ultraviolet spectra during photolysis are compatible with the formation of conjugated double bonds along the main chain; in air, these changes are supplemented by oxidation which results in carbonyl formation along the chain and a relatively small fragment absorbing at about 340 millimicrons.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 16, 1965
- Accession Number
- AD0617952
Entities
People
- F. E. Saalfeld
- L. G. Isaacs
- M. V. Mcdowell
- R. B. Fox
Organizations
- United States Naval Research Laboratory