Determination of crosslink densities of filled rubbers by cyclic pre-straining.

Faridah Hanim A. H., . and Tinker A. J., . and Farid A. S., . Determination of crosslink densities of filled rubbers by cyclic pre-straining. pp. 248-264. ISSN 1511-1768

Physically effective crosslink densities are determined for gum calcium carbonate-filled and carbon black-filled vulcanisates by using cyclic pre-straining ( scragging ) prior to stress-strain measurements to obtain the Mooney-Rivlin constant C1. The procedure was shown to be valid for natural rubber (NR) vulcanisates. Calcium carbonate was found not to interfere in sulphur vulcanisation whereas carbon black increased the yield of crosslinks. The scragged C1 procedure was not applicable to high acrylonitrile (41) -butadiene rubber (NBR) due to difficulties ascribed to hysteresial effects arising from the relatively high glass-transition temperature (Tg) of therubber. For gum NBR vulcanisates crosslink densities were overe-stimated by about 13. The procedure gave extremely low estimates of crosslink density for calcium carbonate-filled NBR vulcanisates but some empirical relationships provided estimates that were in excellent accord with the values for comparable gum vulcanisates. Crosslink densities for black-filled NBR vulcanisates were determined by equilibrium swelling with appropriate corrections for swelling restriction by the carbon black and comparison with values determined from scragged C1 measurements showed the latter to be about 10 higher. Again carbon black increased the yield of crosslinks.

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Abstract

Physically effective crosslink densities are determined for gum calcium carbonate-filled and carbon black-filled vulcanisates by using cyclic pre-straining ( scragging ) prior to stress-strain measurements to obtain the Mooney-Rivlin constant C1. The procedure was shown to be valid for natural rubber (NR) vulcanisates. Calcium carbonate was found not to interfere in sulphur vulcanisation whereas carbon black increased the yield of crosslinks. The scragged C1 procedure was not applicable to high acrylonitrile (41) -butadiene rubber (NBR) due to difficulties ascribed to hysteresial effects arising from the relatively high glass-transition temperature (Tg) of therubber. For gum NBR vulcanisates crosslink densities were overe-stimated by about 13. The procedure gave extremely low estimates of crosslink density for calcium carbonate-filled NBR vulcanisates but some empirical relationships provided estimates that were in excellent accord with the values for comparable gum vulcanisates. Crosslink densities for black-filled NBR vulcanisates were determined by equilibrium swelling with appropriate corrections for swelling restriction by the carbon black and comparison with values determined from scragged C1 measurements showed the latter to be about 10 higher. Again carbon black increased the yield of crosslinks.

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Item Type:	Article
AGROVOC Term:	Density
AGROVOC Term:	Carbon black
AGROVOC Term:	Vulcanization
AGROVOC Term:	Calcium carbonate
AGROVOC Term:	Rubber
AGROVOC Term:	Polymers
AGROVOC Term:	Cross-linking
Geographical Term:	Malaysia
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	28 Apr 2025 03:18
URI:	http://webagris.upm.edu.my/id/eprint/23140

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