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Structural characterization of vulcanizates. Part IX. Comparison of the vulcanization of natural rubber and cis ‐ trans ‐isomerized natural rubber with sulfenamide‐accelerated sulfur and dicumyl peroxide vulcanization systems
Author(s) -
Elliott D. J.,
Moore C. G.
Publication year - 1967
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.1967.070111115
Subject(s) - vulcanization , sulfenamide , peroxide , natural rubber , sulfur , elastomer , polymer chemistry , chemistry , butyl rubber , materials science , organic chemistry
Large variations in the microstructure of 1,4‐polyisoprenes, from ca. 100% cis ‐trialkylethylene groups, as in natural rubber (NR), to ca. 40% cis ‐ and 60% trans ‐trialkylethylene groups, as in an equilibrium‐isomerized NR, have little influence on the overall chemistry of vulcanization of the polyisoprenes by a N ‐cyclohexylbenzothiazole‐2‐sulfenamide‐accelerated sulfur system or by a dicumyl peroxide system. The peroxide crosslinks the equilibrium‐isomerized NR more efficiently than it crosslinks NR; this is attributed to the sulfur dioxide, which is used to isomerize the NR, scavenging some of the nonrubber constituents in the NR, which are known to compete with the rubber hydrocarbon for reaction with free radicals from the peroxide. By comparison with NR vulcanizates, the corresponding equilibrium‐isomerized NR vulcanizates have higher values of the C 2 term of the Mooney‐Rivlin stress–strain equation and higher χ (polymer–swelling liquid interaction parameter) values of the Flory‐Huggins equation.