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Effect of double bonds on the γ‐radiation‐induced crosslinking of polyethylene
Author(s) -
Mitsui Hiroshi,
Hosoi Fumio,
Ushirokawa Masahiro
Publication year - 1975
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1975.070190204
Subject(s) - monomer , polyethylene , polymer chemistry , materials science , chain scission , irradiation , absorbed dose , radiation , double bond , molar mass distribution , molecule , polymer , chemistry , organic chemistry , composite material , physics , quantum mechanics , nuclear physics
Various low‐density polyethylenes ranging in initial weight‐average molecular weight (M̄ w ) from 7600 to 589000 having a ratio of M̄ w to number‐average molecular weight (M̄ n ) of about 5 were irradiated by γ‐rays in vacuo at 30°C. Gel fractions were determined and analyzed by using the equation derived by Charlesby and Pinner. The following relationships were obtained when M̄ w was used as the molecular weight:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{rcl} r_g&=&2.85\times 10^3 \bar{M}_w^{-1}[{\rm C}\hbox{=\hskip-1pt=}{\rm C}]_0 ^{ - 0.21}\\ q_0&=&5.98\times 10^{-3}[{\rm C}\hbox{=\hskip-1pt=}{\rm C}]_0 ^{0.21}\\ p_0&=&2.98\times 10^{-3}[{\rm C}\hbox{=\hskip-1pt=}{\rm C}]_0 ^{0.21}\\ \end{array} $$\end{document}where r g represents the gel point dosage (Mrad), [CC] 0 is the sum of the initial contents of terminal vinyl and vinylidene unsaturations (mole/g polyethylene), and q 0 and p 0 are the probabilities of crosslinking and main‐chain scission per monomer unit for a unit radiation dose in Mrad, respectively. Similar relationships to the equations described above were also obtained when M̄ n was used. From the results, it was concluded that terminal vinyl and vinylidene unsaturations play an important role for the gel formation in the γ‐radiation‐induced crosslinking of polyethylene in vacuo at room temperature.