Radiation chemistry of high polymers. Final report

Technical Report · Sat Jan 01 04:00:00 EST 1977

OSTI ID:5017414

Dole, M; Welch, R A

Work on calibrating the radiation intensity in our ..gamma..-ray source as a function of height and horizontal displacement was completed. For extended chain (high crystallinity) polyethylene (PE) before and after quenching from the melt irradiated at room temperature, the crosslinking yield increased twofold on lowering the crystallinity from 96 to 70%. The G-value for alkyl radical production was about 75% higher in the quenched extended chain sample as compared to the value before quenching. The G (alkyl) values were determined for irradiations at 77K. The rate of decay of the alkyl radicals in PE samples of single crystals having different stem lengths was studied at 80 and 85/sup 0/. It was found that the mole fraction of the slowly decaying free radicals increased with the stem length. Hydrogen gas was found to catalyze both the slow and fast decays. Because hydrogen does not dissolve in the crystalline regions of the PE, the catalytic effect must occur at the amorphous boundary of the crystalline stems. With respect to the kinetics of the allyl radical, either it was found that the data could be explained in terms of two simultaneous but spatially separated second order reactions. As the temperature is raised to 135/sup 0/, the two reactions merge into one. Hydrogen gas has no effect on the decay of the allyl radicals. In the case of the highly crystalline extended chain samples, the allyl decay in some cases follows the simple kinetic equation (1/c) - (1/c/sub 0/) = k..sqrt..t, where k is called a time independent diffusion controlled reaction rate constant. The less the crystallinity of the sample the greater the k constant. A preliminary study of isotactic polypropylene (PP) was carried out and a definite hydrogen gas catalysis of the free radical decay in PP was seen. Similarly in crystalline 1-leucine the hydrogen catalytic effect could also be clearly demonstrated.

• Research Organization: Baylor Univ., Waco, Tex. (USA)
• DOE Contract Number: EY-76-S-05-4059
• OSTI ID: 5017414
• Report Number(s): ORO-4059-7
• 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
ALKYL RADICALS
ALLYL RADICALS
AMINO ACIDS
BEAMS
CARBOXYLIC ACIDS
CATALYSIS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CROSS-LINKING
CRYOGENIC FLUIDS
CRYSTALLIZATION
ELECTROMAGNETIC RADIATION
ELEMENTS
FLUIDS
G VALUE
GAMMA RADIATION
HYDROGEN
IONIZING RADIATIONS
KINETICS
LEUCINE
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHASE TRANSFORMATIONS
PHOTON BEAMS
POLYETHYLENES
POLYMERIZATION
POLYMERS
POLYOLEFINS
POLYPROPYLENE
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
REACTION KINETICS
TEMPERATURE DEPENDENCE