Coral Derived Nano Calcium Carbonate Incorporated Acrylonitrile Butadiene Rubber Composites: Green Look at Properties

Synthesizing nanofillers from bioresources in a cost-effective way is a practical approach to manage waste and circular economy. This paper highlights the preparation of nano-calcium carbonate (NCC) from dead coral exoskeleton by a simple hydrothermal method. The NCC was characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area analysis. NCC with a particle size of 10-20 nm was obtained by this method. A two-roll mill was used to make the nanocomposites of acrylonitrile-butadiene rubber (NBR) with NCC at various filler concentrations (3, 6, and 9 phr). The cure, physico-mechanical, thermal, swelling, and dynamic properties of the composites were investigated. The mechanical and technological properties of NBR were improved by the incorporation of NCC. About 89% increase in tensile strength was observed with the inclusion of 3 phr NCC to the NBR-Gum. The thermal stability of NBR (Tmax) was increased from 450 °C to 455 °C by the addition of 3 phr NCC. Furthermore, the 9 phr NCC composite showed an 18% lower swelling index and 27% higher crosslink density compared to NBR-Gum. The glass transition temperature of NBR increases from -4.70 to -3.29 °C with the addition of 3 phr NCC. The highest Payne effect was observed for NBR-NCC 9 phr composite, indicating effective filler-filler network formation.