ESR Studies of Free Radical Decay in Irradiated Polyethylene
Journal Article
·
· Journal of Chemical Physics
A study was made of the temperature and rates at which molecular hydrogen is evolved and free radical decay occurs when semicrystalline polyethylene, irradiated at liquid-nitrogen temperature, is warmed to room temperature. Hydrogen evolution and free radical decay roughly parallel each other. The temperature of half reaction is the same as the temperature of the gamma-maximum in the mechanical dispersion temperature curve. At constant temperature over the temperature range -71 to 41 deg C, the free radical decay is first order and the free radical concentration seems to decrease to a limiting value at each temperature. The first-order decay constants are approximately constant with temperature. The data are interpreted in terms of free radicals decaying in spurs. If a constant activation energy of 15 kcal mole-1 is assumed, the frequency factors decrease with rise of temperature. This decrease is interpreted on the basis of a decreasing probability of reaction for those free radicals that escape reaction at low temperatures, but react at higher and higher temperatures. An alternative model, based upon the release of free radicals from traps as the temperature is raised, is also discussed, The reaction rate constant for free radical decay calculated from D -- H exchange experiments agrees with that deduced from the ESR measurements. It is also concluded that the persistent free radical in polyethylene irradiated to moderate doses is the allyl free radical.
- Research Organization:
- Northwestern Univ., Evanston, Ill.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-008169
- OSTI ID:
- 4752844
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 37; ISSN 0021-9606
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
ESR STUDIES OF RADIATION GRAFT COPOLYMERIZATION OF POLYETHYLENE AND STYRENE
Radiation chemistry of polyethylene. XIV. Allyl radical decay kinetics in different types of polyethylene. [. gamma. rays]
KINETICS OF DISAPPEARANCE OF RADICALS TRAPPED IN IRRADIATED POLYETHYLENE
Journal Article
·
Mon Dec 31 23:00:00 EST 1962
· Proc. Japan Conf. Radioisotopes
·
OSTI ID:4689009
Radiation chemistry of polyethylene. XIV. Allyl radical decay kinetics in different types of polyethylene. [. gamma. rays]
Journal Article
·
Tue Feb 28 23:00:00 EST 1978
· J. Polym. Sci., Polym. Phys. Ed.; (United States)
·
OSTI ID:6847839
KINETICS OF DISAPPEARANCE OF RADICALS TRAPPED IN IRRADIATED POLYETHYLENE
Journal Article
·
Sun Jul 01 00:00:00 EDT 1962
· Journal of Chemical Physics (U.S.)
·
OSTI ID:4806335