000			02065nam a2200301Ia 4500
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100			_aFaridah H A H
245		0	_aDetermination of crosslink densities of filled rubbers by cyclic pre-straining
260			_bJournal of Rubber Research _c2004
300			_a248-264
520			_aPhysically effective crosslink densities are determined for gum, calcium cabonate-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 cabonate 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 acronitrile (41;)-butadiene rubber (NBR) due to difficulties ascribed to hysteresial effects arising from the relatively high glass-transition temperature (Tg) of the rubber. 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 emperical 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.
650			_aCalcium carbonate
650			_aCarbon black
650			_aCrosslink
650			_aCyclic
650			_aDensity
650			_aDetermination
650			_aFilled rubbers
650			_aGum
650			_aNBR
650			_aNR
650			_aPre-straining
650			_aScragging
650			_aVulcanisates
700			_aFarid A S
700			_aTinker A J
942			_cJS
999			_c56883 _d56883