The effect of carbon black filler on the pyrolysis behaviour of vulcanized cis-polybutadiene

Abstract

The pyrolysis-gas chromatographic analysis at 770° C of two series of vulcanized products of a standard mixture of polybutadiene Buna cis 132 as the rubber component and sulphur as the cross-linking agent, in the presence and absence of a carbon black as a filler has been studied. In both series the density of cross-linking was varied by changing the vulcanization time. Definite correlations were found between the ratio of peak areas toluene/4-vinylcyclohexene and the degree of swelling and the shear modulus. Curie-point pyrolysis of a third series of vulcanized products in which the carbon black content was varied between 0 and 40%, with the vulcanization time being constant (70 min), showed a distinct increase of the same ratio of peak areas with increasing content of carbon black and increasing mechanical strength. As the pyrograms of the unvulcanized mixtures do not reveal any dependence of the ratio on carbon black content, and pyrolysis-gas chromatography in general is only sensitive to changes in chemical bonding, the change of ratio with increasing filler content in the vulcanized products should be attributed to the formation of additional chemical bonds between the primary molecules and the carbon black particles.