New Chloroprene Rubber/Styrene–Butadiene Rubber (CR/SBR) Blends Cross-Linked with Tin(II) Oxide (SnO): Curing Characteristics, Swelling Studies, Mechanical Properties, and Flame Resistance

This study aimed to investigate the properties of tin(II) oxide (SnO) as an unconventional cross-linking agent for chloroprene (CR) and styrene-butadiene (SBR) rubbers compositions. The use of tin(II) oxide results from the need to reduce the use of zinc oxide as a cross-linking agent due to environmental regulations and its toxic impact on aquatic environments. The studied elastomeric blends can be cross-linked with tin(II) oxide, and the results demonstrate the significant potential of this oxide in such applications. The CR/SBR vulcanizates cross-linked with SnO exhibit good mechanical properties and a high degree of cross-linking. The studies clearly show that the proportions of both rubbers as well as the amount of tin(II) oxide used influence the cross-linking of the CR/SBR blends and the properties of vulcanizates. FTIR spectrum analysis allowed the identification of the cross-linking mechanism, which followed the Friedel-Crafts alkylation reaction mechanism. The AFM analysis determined the miscibility of the rubbers and interelastomeric reactions, proving that the rubbers studied are partially miscible. The results of the oxygen index measurements indicated that the obtained vulcanizates showed flame resistance and self-extinguishing properties. Multivariate regression was performed to fit the models to the experimental value and to determine the influence of the content of the cross-linking agent and the CR and SBR proportions on the properties of the blends.