Solid-state NMR of vulcanized natural rubber/butadiene rubber blends: Local organization and cross-linking heterogeneities This article is part of the virtual special issue " Solid-state NMR studies on polymers and biological solids"

Elastomer blends, among which natural rubber (NR) and butadiene rubber (BR), are involved in many components of the automotive/tire industry. A comprehensive understanding of their mechanical behavior requires, among other features, a detailed description of the crosslink density in these mixtures. In the case of vulcanized immiscible blends, the distribution of the cross-link density within each of the NR- and BR-rich domains is key information, but difficult to determine using the conventional approaches used for one-component crosslinked elastomers. In this study, the vulcanization within NR/BR blends is investigated using a robust 1 H double-quantum (DQ) MAS recoupling experiment, BaBa-xy16. Two kinds of cross-linked NR/BR blends were considered with two different microstructures for the BR component. The bulk organization of the resulting blends was first probed by analyzing the 1 H spin-lattice relaxation behavior. In a second step, BaBa-xy16 was used to investigate, in a selective way, the cross-link heterogeneities within NR/BR blends. In particular, for immiscible NR/BR mixtures, the distribution of the cross-link density between both phases was compared and the observed differences were discussed. (c) 2024 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).