Cure Characteristics and Mechanical Properties of ZnO Nanoparticles as Activator in Unfilled Natural Rubber

Abstract

In this work, the effect of ZnO nanoparticles as activator is studied in unfilled natural rubber and compared with conventional ZnO on cure characteristics and mechanical properties. ZnO nanoparticles are synthesized by precipitation method using zinc nitrate tetrahydrate and sodium hydroxide as precursor. Particle size of ZnO nanoparticles can be controlled by polymeric additive. It is found that the average primary size of synthesized ZnO nanoparticles around 28.71 nm and the specific surface area around 31.45 m2/g. The crystalline structure exhibits hexagonal structure with wurtzite. The rheological properties of unfilled natural rubber show that the maximum torque (MH) and the optimum cure time (t90) increase with increasing synthesized ZnO nanoparticles loading. The minimum torque (ML) of unfilled natural rubber which uses synthesized ZnO nanoparticles loading higher than conventional ZnO. Compression set and tension set are the permanent deformation also investigated. It is found that deformation reduces when increase synthesized ZnO nanoparticles loading. The mechanical properties such as hardness, tensile strength, 100% and 300% modulus, tear strength, elongation at break are improved, without detrimental effect on properties. For unfilled natural rubber, synthesized ZnO nanoparticles can be reduced successfully from 5 to 2 phr and stearic acid 1 to 0.3 phr, respectively.