Effect of green synthesized zinc oxide nanoparticles as cure activator on the mechanical properties of natural rubber vulcanizate

In this study, zinc oxide nanoparticles mediated with mango leaves (Magnifera Indica) extract were synthesized, characterized and used as cure activator in natural rubber vulcanizate. The extract was reacted with zinc acetate in a ratio of 1:1 with the addition of NaOH, stir-heated, centrifuged and dried to obtain the nanoparticles. The absorption spectrum of the as-synthesized nanoparticles gave characteristic peak at 384.5 nm, Energy-dispersive X-ray (EDX) analysis gave elemental composition of 64.84% Zn, 18.88% O and 16.19% C, whereas the Scanning Electron Microscopy (SEM) displayed irregular and polydisperse nanoparticles. From the Transmission Electron Microscopy (TEM) results, the average particle diameter obtained was 65.19 nm. Natural rubber was compounded separately using the synthesized ZnO nanoparticles (nZnO) and conventional zinc oxide (cZnO) at 0, 2, 4, 5 phr loadings. The effect of the different loadings of the ZnO on the cure characteristics and mechanical properties of natural rubber vulcanizate was determined. The results showed an optimum cure time for the nZnO at 2phr loading to be same with the 5phr of the conventional ZnO. A progressive increase in tensile strength, modulus (300%), hardness, compression set and elongation at break was seen for both compounds at attainment of optimum cure time but witnessed a reduction beyond optimum cure time. nZnO is therefore a better alternative to cZnO as a cure activator in rubber as it exhibited interesting properties with reduced concentration of ZnO and at a fast cure time.