A novel system for measurement of types and densities of sulfur crosslinks of a filled rubber vulcanizate

A novel system for measuring the crosslink densities of mono-, di- and polysulfides of a filled rubber vulcanizate was developed. The system included pre-swelling, cleavage of sulfur crosslinks by a chemical probe using thiol/n-hexylamine instead of thiol/piperidine, and two step swelling. A sample cage made of stainless steel mesh was used to measure multiple samples at the same time and to reduce experimental errors. The organic materials-extracted sample was pre-swollen in toluene to introduce the probe chemicals more rapidly and homogeneously into the whole network. Polysulfidic crosslinkages were cleaved by a chemical probe of propane-2-thiol/n-hexylamine in toluene, while di- and polysulfidic crosslinkages were dissociated by a chemical probe of n-hexanethiol/n-hexylamine in toluene. The experimental errors were lower than 2%. By using cubic apparent crosslink density, fractions of the crosslink types of an unknown rubber vulcanizate could be estimated even although the filler content and rubber composition are not analyzed. (C) 2014 Elsevier Ltd. All rights reserved.