Effect of zinc oxide nanoparticles synthesized by a precipitation method on mechanical and morphological properties of the CR foam

ZnO nanoparticles were synthesized by a precipitation method in aqueous media from zinc nitrate hexahydrate and sodium hydroxide. The synthesized ZnO nanoparticles exhibited a crystalline structure with hexagonal structure of the wurtzite. The morphology of the synthesized ZnO nanoparticles presented a spherical shape with the average primary size of 54.53 nm and the specific surface area of 20.28 m(2) g (-1). The effect of the synthesized ZnO nanoparticles by the precipitation method as a crosslinking agent for chloroprene rubber foam (CR foam ) on cure characteristics, mechanical properties and morphologies was investigated. The aim of this study is to vary the synthesized ZnO nanoparticles' level in the range of 0.5-5 parts per hundred parts of rubber (phr) compared with the conventional ZnO at 5 phr. The rheological characterization showed that the maximum torque (M (H) ), the minimum torque (M (L) ), the differential torque (M (H)- M (L) ) and Mooney viscosity increased with the increase in synthesized ZnO nanoparticles' content, whereas the optimum cure time (t (90) ) and scorch time (T5) decreased. On the other hand, the mechanical properties such as hardness, tensile strength and specific gravity were improved. For CR foam, the results compared to the amount of conventional ZnO, only 60 wt% (3 phr ) nano-ZnO was enough to obtain similar cure characteristics and mechanical properties. The synthesized ZnO nanoparticles showed the mechanical properties higher than conventional ZnO because of small particle size and large specific surface area which led to the increase in the degree of crosslinking.