Effect of Oyster Shell Powder Loading on the Mechanical and Thermal Properties of Natural Rubber/Oyster Shell Composites

The oyster shell powder/natural rubber composites were successfully prepared by blending the modified oyster shell powder with natural rubber (NR). The oyster shell powder with a particle size of 209 nm were well distributed within the rubber matrix. The characteristic Fourier transform infrared spectroscopy (FTIR) absorption bands of both oyster shell powder and natural rubber were observed in the FTIR spectra of NR/oyster shell powder composites. The C-O absorption bands in carbonates of composites exhibit a shift from 1425 cm−1 to 1446 cm−1 which suggests the bonds formed among oyster shell powder, earth coupling agent and NR. The tensile strength and stress at 500% elongation increased with rising of the earth coupling agent. Composites with 1.5 parts per hundred rubber (phr) coupling agent achieved the highest mechanical properties, where an increase of 13.4% in tensile strength was found. The tensile strength and tear strength increased along with an increment of oyster shell powder. When the content of oyster shell powder attained 25–30 phr, the composites exhibited the best mechanical properties. In particular, the tensile strength and tear strength increased by 27.9% and 17.2% when compared with those of the control samples. Furthermore, the addition of the oyster shell powder leads to the improvement of thermal stability which is evidenced by an increase of 8 °C in the initial degradation temperature. The improvement of the mechanical properties and thermal stability of the composites have demonstrated that the oyster shell powder can be used as potential fillers for natural rubber.