UNCONVENTIONAL RUBBER NETWORKS: CIRCUMVENTING THE COMPROMISE BETWEEN STIFFNESS AND STRENGTH

The failure properties of rubbery networks exhibit a maximum as a function of cross-link density or modulus. To avoid excess creep, elastomers are usually formulated such that their state of cure falls past this maximum, which means there is an inevitable compromise between modulus and failure properties (stiffness and strength). This review describes various approaches to circumventing the problem by the use of unconventional network structures. The obtainable improvements in mechanical properties can be substantial (e.g., threefold increases or greater in strength), although these methods entail additional processing steps or the use of blends and may affect the hysteresis of an elastomer; thus, their practical utility cannot be assessed a priori.