THE LET-DEPENDENCE OF THE RADIATION REACTIONS OF POLYVINYL ACETATES IN SOLUTION

Journal Article · Mon Jan 01 00:00:00 EST 1962 · Makromolekueare Chemie (Switzerland)

OSTI ID:4828978

Henglein, A; Schnabel, W; Heckel, E

Solutions of polyvinyl acetate in trimethylborate were exposed to Co/sup 60/- gamma radiation, to 120 kev-bremsstrahlung, and to thermal neutrons at various dose rates. The observed effects were independent of dose rate. However, they strongly depended on the LET (linear energy transfer) of the radiations. Gamma and x rays rapidly crosslinked the polymer. The densely ionizing He/sup 4//Li/sup 7/-particles from the exothermic nuclear reaction B/sup 10/ + n yields He/sup 4/ + Li/sup 7/ caused degradation of the polymer. Solutions that were solidified beyond the gel point under gamma -irradiation became liquid again when subsequently exposed to He/sup 4//Li/sup 7/-radiation. These experiments showed that the ratio p/sub O/q/sub O/ (p/sub O/, q/sub O/: sp ecific degradation and crosslinking densities) increases with increasing LET. Several mechanisms are discussed which may basically explain LET effects in polymers. Two classical'' explanations in terms of different initial concentrations of intermediate radiolysis products in the tracks of ionizing particles are given: q/sub O/ may be decreased by the depression of transfer reacttons between solvent radicals and intact macromolecules in favor of radical- radical reactions at high LET; p/sub O/ may be increased at high LET since primary recombinations of end-group-macroradicals will be prevented by solvent radicals in the same cage. Another explanation considers multiple ionization and excitation of molecules by particles of high LET. Dissociation of multiply ionized macromolecules may result in a complete change of the ratio p/sub O//q/ sub O/. Furthermore, the introduction of several radical spots into one macromolecule may lead to intramolecular instead of intermolecular crosslinking. (auth)

• Research Organization: Hahn-Meitner-Istitut fur Kernforschung, Berlin
• NSA Number: NSA-16-020501
• OSTI ID: 4828978
• Journal Information: Makromolekueare Chemie (Switzerland), Vol. Vol: 49; Other Information: Orig. Receipt Date: 31-DEC-62
• Country of Publication: Country unknown/Code not available
• Language: German

Related Subjects

CHEMISTRY
ACETATES
BORATES
BORON 10
BREMSSTRAHLUNG
COBALT 60
COLLOIDS
DECOMPOSITION
ENERGY LOSSES
EXCITATION
GAMMA RADIATION
HELIUM 4
LET
LITHIUM 7
METHYL RADICALS
NEUTRON BEAMS
NUCLEAR REACTIONS
PARTICLE TRACKS
POLYMERIZATION
POLYVINYLS
RADIATION CHEMISTRY
RADIATION DOSES
RADIATIONS
RADIOLYSIS
REACTION KINETICS
SOLIDIFICATION
SOLUTIONS
THERMAL NEUTRONS
X RADIATION