Studies on the role of hydroxyapatite nanoparticles in imparting unique thermal, dielectric, flame retardancy and petroleum fuel resistance to novel chlorinated EPDM/chlorinated NBR blend

Novel elastomeric blend nanocomposites of chlorinated nitrile rubber (Cl-NBR) and chlorinated ethylene-propylene-diene rubber (Cl-EPDM) with different contents of nano-hydroxyapatite (HA) were prepared. The formation of blend nanocomposite was analyzed by FTIR, XRD, TEM, SEM and TGA. The fire resistance, dielectric behavior and diffusion of petroleum fuels through the blend membrane had been investigated as a function of nanoparticle loading. The FTIR revealed the absorption band of HA in the rubber blend indicated the effective interaction between HA nanofiller and the rubber blend. XRD plots indicated a reduction in amorphous region of rubber blend with the addition of nanoparticles. TEM and SEM images revealed the uniform dispersion of nanoparticles in the rubber blend. TGA results indicated that the thermal stability of rubber blend nanocomposite was higher than Cl-NBR/Cl-EPDM blend. Increased fire resistance of blend composites obtained from limiting oxygen index demonstrated that hydroxyapatite nanoparticles were served as an excellent fire-retardant additive for Cl-NBR/Cl-EPDM blend. Improvement in dielectric constant with the loading of nanoparticles indicated the reinforcement of blend matrix by the HA nanoparticles. The solvent uptake of blend nanocomposite decreased up to 7 phr HA-loaded sample. A decrease in solvent uptake was also observed with the increase in molecular size of the penetrant molecules. The mechanism of diffusion was anomalous in nature. Overall, the sample with 7 phr of HA-filled rubber blend showed a remarkable increase in dielectric properties, flame resistant and minimum solvent uptake.