RADIATION CROSSLINKING OF RUBBER. III. CHAIN FRACTURE

Journal Article · Tue Mar 01 04:00:00 EST 1960 · J. Polymer Sci.

DOI:https://doi.org/10.1002/pol.1960.1204314104· OSTI ID:4144580

Mullins, L; Turner, D T

Purified natural rubber was exposed in vacuo to a 4-Mev electron beam and attempts were made to estimate the ratio of fractures of the main chain of carbon atoms to crosslinks, using three different methods. Measurements of the sol fraction (S) as a function of the radiation dose (R) did not conform to a linear relationship between S + S/sub 1/2/ and R/sup -1/ reported by Charlesby and Pinner for a number of other polymers. Little consummated random fracture appeared and the sol fraction tended toward zero at radiation doses above about 50 Mrad. The stress in rubbers maintained at constant elongation decreased continuously on irradiation, and rigorous exclusion of traces of air and impurities was of critical importance. Deficiencies of previous analyses of stress-relaxation data are discussed and an attempt made to provide an internally consistent treatment of the data. A value for beta of 0.18 was obtained when no allowance wss made for chain entanglements, a value of 0.03 was obtained when such allowance was made. This very low value may be due to the inadequacy of the assumption made tbat fracture releases entanglements. In a third method stress- strain measurements of irradiated rubber provided estimates of the number-average molecular weights of both the chain segments between adjacent crosslinks and the primary molecular chains. Comparison with similar data for vulcanizates prepared by thermal decomposition of di-tert-butyl peroxide gave a value for beta of 0.11. This value was calculated on the assumption that no fracture occurs on formation of the peroxide vulcanizates. The nominal G(X) value of 0.9 is increased to 1.05 when an allowance is made for fracture. (auth)

• Research Organization: British Rubber Producers' Research Assn., Welwyn Garden City, Herts., Eng.
• NSA Number: NSA-14-013027
• OSTI ID: 4144580
• Journal Information: J. Polymer Sci., Journal Name: J. Polymer Sci. Vol. Vol: 43
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

AIR
ATOMS
BUTYL RADICALS
CARBON
DECOMPOSITION
DEFORMATION
ELECTRON BEAMS
EXPANSION
HEATING
IMPURITIES
IRRADIATION
LATTICES
MATHEMATICS
METALS, CERAMICS, AND MATERIALS
OXIDES
PEROXIDES
POLYMERIZATION
POLYMERS
QUANTITATIVE ANALYSIS
RADIATION DOSES
RADIATION EFFECTS
RUBBER
STRESSES
VACUUM
VULCANIZATION
WEIGHT