Study of the effect of different shapes of ultrafine silica as filler in natural rubber compounds

The effects of different particle shapes of ultrafine silica used as a filler on the properties of natural rubber compounds were investigated. Three shapes of filler (cubical, elongated and irregular) were produced using the Hosokawa Alpine classifier mode with a 50 ATP-forced vortex classifier. Each filler was loaded into SMR-L natural rubber at four different loadings, 10 to 40 parts per hundred rubber (phr). The curing characteristics, tensile properties and morphology were studied to measure the performance of the filler. Variations of the particle shape of ultrafine silica did not affect the scorch time and cure time of natural rubber compounds. However, at higher loading, elongated-shaped filler showed a higher maximum torque compared with cubical or irregular shaped fillers. Because of better filler-rubber interaction, irregular shaped fillers showed the highest tensile strength, elongation at break and hardness compared with the cubical and elongated shapes