Accession Number : AD0617952

Title :   PHOTODEGRADATION OF HIGH POLYMERS. PART VI. PHOTOLYSIS OF POLYSTYRENE FILMS IN VACUUM AND IN AIR.

Descriptive Note : Interim rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON D C

Personal Author(s) : Fox,R. B. ; Isaacs,L. G. ; Saalfeld,F. E. ; McDowell,M. V.

Report Date : 16 JUN 1965

Pagination or Media Count : 19

Abstract : Thin films of polystyrene have been photolyzed by 2537A radiation in vacuum and in air at 25, 80, and 120C. 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 to 120C 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 photlysis 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. (Author)

Descriptors :   (*STYRENE PLASTICS, PHOTOCHEMICAL REACTIONS), (*PHOTOCHEMICAL REACTIONS, STYRENE PLASTICS), POLYMERS, FILMS, DEGRADATION, VACUUM, AIR, ULTRAVIOLET RADIATION, MOLECULAR PROPERTIES, MASS SPECTROSCOPY

Distribution Statement : APPROVED FOR PUBLIC RELEASE