Comparative study of vulcanization characteristics between centrifugally spun ZnO fibers and commercial ZnO nanoparticles in natural rubber

In response to environmental concerns associated with the overuse of zinc oxide (ZnO) in rubber vulcanization, this study investigates the potential of novel ZnO fibers synthesized via centrifugal spinning as alternative vulcanization activators in natural rubber. Developing more efficient ZnO morphologies capable of maintaining vulcanization performance at reduced ZnO loadings has become an important research objective. At first, Composite fibers were prepared using zinc nitrate and polyvinylpyrrolidone by centrifugal spinning from the corresponding solution. These fibers were then annealed at 500 °C to yield pure ZnO fibers and subsequently milled to achieve homogeneity. The vulcanization behaviour of natural rubber compounds formulated with these ZnO fibers (composite, annealed, and milled) was compared to that of commercial ZnO powders (Silox 2C and Zinkoxid RAC). Characterization included analysis of the morphology and structure of fibers and particles, measurement of vulcanization kinetics (t 95 ), activation energy, crosslink density, and mechanical properties, such as tensile strength, elongation at break, tear resistance, and hardness. Results showed that annealed and milled ZnO fibers exhibited comparable or, in some tests, better performance than commercial ZnO powders, with enhanced crosslink density and mechanical strength. The findings indicate that ZnO with tailored fiber morphology may enable reduced ZnO loading without compromising performance, representing a promising approach toward reducing the environmental impact of rubber vulcanization.