Fabrication, characterization, dielectric properties, thermal stability, flame retardancy and transport behavior of chlorinated nitrile rubber/hydroxyapatite nanocomposites

Abstract

This work focused on the preparation of chlorinated nitrile rubber (Cl-NBR)/hydroxyapatite (HA) nanocomposites by an open two-roll mixing mill. The formation of nanocomposites was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The dielectric properties and flame retardancy of polymer nanocomposites were analyzed with special attention to the loading of HA nanoparticles. Diffusion and permeation properties of petroleum solvents through the prepared Cl-NBR/HA composites were also investigated in detail as a function of filler content, different temperatures and nature of solvent. The incorporation of HA in Cl-NBR has been endorsed by FTIR analysis. The XRD showed the crystalline peaks of HA in the polymer chain. SEM images revealed that the nanoparticles were uniformed distributed in the polymer network with spherically shaped particles. TGA results indicated that the thermal stability of nanocomposites was remarkably higher than the pure Cl-NBR and the thermal stability increases with the loading of nanoparticles. The dielectric study observed a decreasing dielectric constant with increasing frequency, and the maximum property was obtained for 7 phr HA filling in Cl-NBR. The flame resistance of the polymer composites was greatly enhanced by the incorporation of nanoparticles. The diffusion, sorption and permeation constants were found to decreased with increase in HA content. The solvent uptake decreases with the size of the penetrant molecules, and the mechanism of transport of Cl-NBR composite was anomalous in nature. The enthalpy and entropy changes of the nanocomposites were analyzed from the diffusion data. The composite containing 7 phr HA sample showed higher dielectric properties and better solvent resistance properties.