Degradation of polystyrene by gamma irradiation: effect of air on the radiation-induced changes in mechanical and molecular properties

Journal Article · Sun Jul 15 04:00:00 EDT 1979 · J. Appl. Polym. Sci.; (United States)

DOI:https://doi.org/10.1002/app.1979.070240211· OSTI ID:5938495

Bowmer, T N; Cowen, L K; O'Donnell, J H; Winzor, D J

Irradiation of 3 mm polystyrene sheet in air at 30/sup 0/C with ..gamma.. rays caused a rapid decrease in the tensile and flexural strengths and strains to fracture. These properties were decreased to 50% of their initial values after ca. 80 Mrads and to 25% after ca. 200 Mrads, beyond which dose the rate of change was relatively small. These results contrast with the negligible changes that are observed after 600 Mrads in vacuum. The effect of irradiation in air has been correlated with decreasing molecular weight at the surface, even though crosslinking predominated over the complete sample so that a gel point was reached at a dose slightly in excess of 100 Mrads. Scission and crosslinking yields, G(S) and G(X), were determined as a function of depth by gel permeation chromatography of layers removed progressively from the surface. G(S) decreased and G(X) increased with depth, in accord with the concepts of increased scission by reaction with oxygen and a diffusion effect. Unusual transverse cracking to a limited depth occurred during tensile measurements, a phenomenon that is attributed to the nonuniform molecular weight profile. 9 figures, 1 table.

• Research Organization: Univ. of Queensland, St. Lucia, Australia
• OSTI ID: 5938495
• Journal Information: J. Appl. Polym. Sci.; (United States), Journal Name: J. Appl. Polym. Sci.; (United States) Vol. 24:2; ISSN JAPNA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360406 -- Materials-- Polymers & Plastics-- Radiation Effects-- (-1987)
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
AIR
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
CROSS-LINKING
DECOMPOSITION
ELECTROMAGNETIC RADIATION
FLUIDS
GAMMA RADIATION
GASES
IONIZING RADIATIONS
IRRADIATION
MECHANICAL PROPERTIES
MEDIUM TEMPERATURE
MOLECULAR WEIGHT
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POLYMERIZATION
POLYMERS
POLYOLEFINS
POLYSTYRENE
POLYVINYLS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADIOLYSIS