Modification of starch for high performance elastomer

Because conventional filler carbon black (CB), used for elastomer reinforcement, is wholly dependent on the non-renewable petroleum resource, a novel starch modification for filler-reinforced elastomer is developed using two types of modifiers, i.e. resorcinol-formaldehyde (RF) and a silane surfactant (S). Originally used as a curing agent for rubber vulcanization, the RF is here designed to interact with starch and rubber, and thus improve the interface. The S is expected to improve the dispersion of starch particles and enhance the compatibility. The RF achieved much higher reinforcement than the S. When the starch was co-modified by both, the mechanical property improvement of styrene-butadiene rubber (SBR) was superior to that reinforced by CB. Modification mechanism was explained as that (a) the RF forms oligomer, and (b) the oligomer then undergoes condensation/crosslinking, which combines starch particles and SBR macromolecules firmly. This mechanism was subsequently proved by a suspension experiment, which refers to the experiment that measures the compatibility of modified starches with SBR in solutions of dissolved compounded SBR. Transmission electron microscopy shows that most of the modified starch particles are dispersed on nano-scale; scanning electron microscopy indicates fine morphology achieved by the modification.