Analysis of unbound materials in carbon-black-filled NR vulcanizates

Extraction of unbound materials from carbon-black-filled natural rubber (NR ) vulcanizates with different cure systems was studied using various solven ts with different dielectric constants of n-hexane, toluene, THF, acetone, and acetonitrile. The extraction was performed at room temperature and 40 d egrees C for 2 days and in the boiling solvent for 8 h. Amounts of extracte d materials from the NR vulcanizates increase by increasing the temperature . Amounts of extracted materials from the NR vulcanizates with n-hexane, to luene, and THF are more than those with acetone and acetonitrile. Amounts o f extracted materials from the NR vulcanizate with a high crosslink density are less than those from the NR vulcanizate with a low one. Thermogravimet ric analysis of the NR vulcanizates before and after the extraction were ca rried out to investigate components of the extracted materials. It was foun d that there were polymer components and metal complexes, as well as organi c matters with a low molecular weight in the extracted materials. Abilities of the solvents to extract unbound materials from the NR vulcanizates were discussed. (C) 1999 John Wiley & Sons, Inc.