Approaches Toward In Situ Reinforcement of Organic Rubbers: Strategy and Recent Progress

Organic rubbers, comprising carbon-carbon links in their polymer backbone, are an essential part of modern everyday life. Tough, their unique properties are mainly governed by reinforcing fillers such as carbon black and silica. However, the reinforcing power is not only driven by the chemical nature of fillers but also by their particle size, shape, distribution and dispersion. In order to minimize agglomeration and processing difficulties, the idea of in situ generated fillers has been approached. In situ means "locally" and refers to the generation of fillers during the vulcanization process. This versatile technique provides individual tailoring of rubber compounds due to numerous possible reaction pathways. In situ reinforcement has been reported for all relevant rubber matrixes and is already employed commercially. In this review, a comprehensive overview of possible in situ reinforcing strategies for organic rubbers and their impact on mechanical properties is provided. It covers the reinforcing power of sol-gel derived in situ fillers, metal salts of unsaturated carboxylic acids as well as the formation of interpenetrating networks with resins in detail.