A comprehensive review on active chain density evaluation from swelling and insights for better accounting for insoluble particles

Abstract

AbstractThe present study provides a state of the art on methods for evaluating active chain density of rubbers from swelling experiments. This review focuses more particularly on the effects of components that are known to limit the swelling, and which typically results in an overestimation of the active chain density. These components are commonly considered as insoluble. Different corrections dealing with the two principal insoluble components, namely zinc oxide (Zn0) and carbon black (CB) filler, are thoroughly investigated. A comparative study on the same natural rubber (NR), either filled and unfilled, vulcanized with three different vulcanization systems, is performed to evaluate the relevance of each predictive approach. The results obtained highlight their respective limitations. In particular, it is shown that the swelling ratio of unfilled and filled natural rubbers are linearly related, suggesting that fillers have no significant effect on the overall number of cross‐links formed during vulcanization. As a result, we propose a unified approach for correcting the ZnO content for unfilled NR and both the ZnO and CB contents for filled NR. By comparing with results issued from uniaxial tensile tests, it is shown that the use of a mechanical response is a relevant alternative for determining the active chain density.