Abstract
A new quantitative analytical method to determine the free sulfur content in vulcanized natural rubber was proposed. This method, i. e. a combination of tetrahydrofuran (THF) extraction followed by HPLC analysis in size exclusion chromatography mode, required much less sample compared with that needed in the ordinary sodium sulfite method specified by JIS K 6234 and ASTM D297. The detectable sensitivity of the new method was about hundreds times of the former method. In addition, it was proven that only free sulfur content could be determined by this method whereas the sum of the free sulfur and polysulfide contained in the rubber sample was detected by the ordinary sodium sulfite method.
