Influence of synthesized nano-ZnO on cure and physicomechanical properties of SBR/BR blends

This study focuses on the synthesis of zinc oxide (ZnO) nanoparticles by high temperature calcination as well as low-temperature hydrolysis methods and their efficiency as cure activator in styrene-butadiene rubber/ polybutadiene rubber blend. The synthesized nano-ZnO samples were characterized by means of X-ray diffraction, BET surface area and transmission electron microscopy. The synthesized nano-ZnO samples had wurtzite structure and average particle size in the ‘nm’ range. ZnO nanoparticles, synthesized on sepiolite template, were of smallest particle size (maximum number of particles in the range of 7–12 nm) and highest surface area (104 m^2g^-1). Polyethylene glycol (PEG)-6000 coated ZnO nanoparticles had rod-like structure; average diameter of the rods was 50 nm. In the case of PEG-coated ZnO containing compounds, optimum cure time of the blend was decreased by 5 min compared to that of standard rubber grade-ZnO containing compound (used as reference). Optimum cure time was lowered by 7–10 min in the case of synthesized nano-ZnO containing compounds compared to the reference ZnO based compound in presence of conventional filler, carbon black. It was also observed from ICP-OES analysis that the presence of very little amount of magnesiumin one of the synthesized ZnO has noticeable impact on cure properties. PEG-coated ZnO increased the tensile strength of gum vulcanizates by 28% compared to the reference ZnO, acting as nanofiller at 3 phr loading. The study of curing behavior in dynamic condition was carried out using DSC. The results differ slightly from static curing except PEG modified nano-ZnO. Use of ZnO nanoparticles could provide faster crosslinking, better reinforcement at lower concentration compared to reference ZnO.