Title: Carbon Black Reinforcement in Pre-Swollen Rubbers
Abstract: Abstract The mechanism of carbon black reinforcement was studied by examining stress-strain properties in SBR 1500 vulcanizates cured while swollen, then de-swollen. Carbon black-polymer attachments started contributing to the modulus of rubber at much higher elongations (ca. 300 per cent for a swelling ratio of 4.0) than in normally cured, unswollen specimens. The modulus in pre-swollen rubbers is considerably lower than in normal vulcanizates but it can be increased by heating the same specimens 30 minutes at 155° C in their de-swollen state. The observed increase in modulus of vulcanizates containing graphitized and regular carbon blacks after such a treatment was found to be related to carbon black “activity” and loading. Bound rubber does not seem to function as a distinct phase contributing to reinforcement, but it can be used as a measure of the number of attachments of carbon black and polymer. Additional information on the molecular mechanism of the phenomenon was obtained through radioactive tracer analysis. It was also found that regular vulcanizates can be softened by heating swollen samples at elevated temperatures (150-170° C). This softening was related to carbon black “activity” and was fully reversible: the original modulus could be recovered by additional heating of de-swollen vulcanizates for a further thirty minutes at 155° C. The above observations are discussed in terms of mobile adsorption of polymer chains on carbon black surface and the steric effect of fixing carbon black particles into an already extended polymer network.
Publication Year: 1966
Publication Date: 1966-11-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 2
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