SYNTHESIS OF GRAFTED COPOLYMERS FROM POLYMERS IRRADIATED BY IONIZING RADIATIONS. II. EFFECT OF THE PREIRRADIATION CONDITIONS OF THE KINETICS OF GRAFTING OF POLYETHYLENE

Journal Article · Thu Jan 01 04:00:00 EST 1959 · J. Polymer Sci.

DOI:https://doi.org/10.1002/pol.1959.1203412733· OSTI ID:4287043

Chapiro, A

The influence of dosage and intensity of pre-irradiation upon the grafting reaction of vinyl monomers has been studied in the case of polyethylene films which were previously irradiated in the presence of air. Several types of radiations were used for irradiation of the films: gamma rays from Co-60, 37-kv x rays, and accelerated electrons at 2 Mev. The irradiated films were heated in vacuo in the presence of monomer, at 80 and 135 C. During grafting the films become regularly thicker in all three dimensions without changing the over-all external shape, even at high degrees of grafting. It was found that the rate of grafting at a given temperature was a linear function of time of preirradiation for doses up to 10 megarads; for the higher doses the rate of grafting is limited. On the other hand, films pre-irradiated in the presence of air and irradiated in vacuo, lose their activity toward grafting. For a given dosage of irradiation, the rate of grafting is highest when the intensity of pre-irradiation is smallest. All these results confirm the hypothesis, previously formulated, that irradiation in the presence of air produces peroxide groups in the polymer. These polymeric peroxides are themselves sensitive to radiolysis and decompose at high doses. The kinetics of the grafting reaction agrees with a polymerization reaction initiated with macroperoxides. This polymerization proceeds in a highly viscous polymeric medium, which slows down the termination reaction and produces effects analogous to those called gel effect. Moreover, the necessity for the monomer of penetrating into the polymeric film complicates the phenomena, the instantaneous concentration of the monomer at the loci of reaction being controlled by diffusion. The influence of the side chains of the high pressure polyethylene on the radiochemical peroxidation has been studied by comparison with grafting carried out on low-pressure polyethylene and polypropylene. The results show that the presence of tertiary hydrogen atoms in polypropylene enhances the formulation of hydroperoxides, while biperoxidic structures prevail in the case of linear polyethylene. All the results are discussed. (auth)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-13-009823
• OSTI ID: 4287043
• Journal Information: J. Polymer Sci., Journal Name: J. Polymer Sci. Vol. Vol: 34
• Country of Publication: Country unknown/Code not available
• Language: French

Related Subjects

AIR
CHEMICAL REACTIONS
CHEMISTRY
COBALT 60
CONFIGURATION
DECOMPOSITION
ELECTRONS
ENERGY LEVELS
FILMS
GAMMA RADIATION
IONIZATION
OXIDES
POLYETHYLENES
POLYMERIZATION
POLYMERS
RADIATION CHEMISTRY
RADIATION DOSES
RADIATION EFFECTS
REACTION KINETICS
THICKNESS
VACUUM
VELOCITY
VINYL RADICALS
VISCOSITY
X RADIATION