Natural rubber composites filled with zinc ferrite nanoparticles: focus on structural, morphological, curing, thermal and mechanical properties

Metal oxide nanofillers are a special type of additives in rubber composites that impart special qualities such as thermal resistance, tensile strength, electrical conductivity and heat capacity to rubbers. The heat conductivity of metal oxide through the rubber matrix reduces the vulcanization time of the rubber nanocomposites. Hence, the present work focused on the enhancement of these properties in natural rubber (NR) using zinc ferrite (ZnFe2O4) nanoparticles were prepared by a simple two-roll mill mixing technique. Structure, morphology, crystalline nature, cure characteristics, swelling, thermal and mechanical properties of the NR composites containing ZnFe2O4 were analysed in detail. FTIR and UV analysis proved the interaction of zinc ferrite with the macromolecular chain of NR. The XRD patterns of composite films revealed a decrease in amorphousness of NR with well-dispersed crystalline peaks of nanoparticles in the polymer. SEM images evidenced the morphological changes caused by dispersing zinc ferrite in the NR matrix. TEM analysis showed the uniform attachment of nanoparticles in the polymer. Glass transition temperature obtained from DSC was improved with the addition of zinc ferrite. The results from TGA showed that the presence of ZnFe2O4 in the polymer matrix greatly increases the thermal stability of NR. The metal oxide nanofiller significantly reduced the cure and scorch time of the NR composites. The mechanical properties of rubber nanocomposites showed that the addition of ZnFe2O4 improved their modulus, tensile strength, hardness, abrasion resistance and heat build-up, whereas the elongation at break and resilience decreases. The permeation and diffusion of nanocomposites were observed to be diminished with the size of penetrating solvents and also with the loading of filler. Overall, zinc ferrite nanoparticles could be used as a potential filler for improving the processability, mechanical strength, thermal stability and solvent resistance of natural rubber.