Irradiation of Polyethylene. III. Influence of Temperature and Phase ¹

Journal Article · Sat Jun 20 04:00:00 EDT 1959 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja01521a001· OSTI ID:4262506

Williams, T. F.; Dole, Malcolm

Gamma-ray irradiation of the linear polyethylene, Marlex-50, above the melting point yields a higher evolution of hydrogen and a greater degree of crosslinking and of vinylene double bond production than irradiation at room temperature. The infrared band at 10.1 mu is missing in the case of the 142 deg C irradiated polyethylene, and the crystallization ability is reduced. Vinyl and vinylene double bond decay constants are increased at the upper temperature, but not markedly so. G values for vinylene decay in the case of Marlex-50 containing 5% of trans-1,4-poly-(butadiene) are as high as 50.6 groups decayed per 100 ev of energy absorbed in the whole sample, but gel formation remains unchanged, leading to the postulate of vinylene decay in this mixture by intramolecular coupling. Material balance between hydrogen evolution, crosslinking and double bond formation is approached in the case of Marlex-50 at both 25 and 142 deg C by allowing for a calculated increase in the weight average molecular weight due to endlinking. It is concluded that both M/sub n/ and M/sub w/ increase by the factor STAVi!/sup o//STAVi! as endlinking occurs. Material balance is not achieved in the case of a low density polyethylene. At the gel point of the latter the decrease in vinylidene unsaturation is estimated to be almost four times as great as cross-links produced, a fact which suggests that vinylidene groups are located near the ends of the molecules. A post-irradiation fusion of vacuum irradiated Marlex-50 causes a greater vinyl decay, increased vinylene group formation a greater G value for crosslinking. These facts suggest strongly that crosslinking can occur by rearrangement of segments containing free radicals as well as by C- C bond formation during the radiolytic detachment of hydrogen. The trans-1,4-poly-(butadiene) lowers G(H/sub 2/) and G(- Vi) at 142 deg C, but the latter more than the former; cis-1,4poly-(butadiene) has a smaller effect. At room temperature the protective action of the poly-(butadiene) seems to be much less, probably because of non-uniform mixing in the solid state. (auth)

• Research Organization: Northwestern Univ., Evanston, Ill.
• Sponsoring Organization: USDOE
• NSA Number: NSA-13-017937
• OSTI ID: 4262506
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 12 Vol. 81; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

BUTADIENE
CHEMICAL REACTIONS
CHEMISTRY
CONFIGURATION
CRYSTALLIZATION
DECAY
DECOMPOSITION
DENSITY
FREQUENCY
GAMMA RADIATION
INFRARED RADIATION
IRRADIATION
MATHEMATICS
MELTING
POLYETHYLENES
POLYMERS
RADIATION DOSES
RADIATION EFFECTS
TEMPERATURE
VACUUM
VINYL RADICALS
WEIGHT