Effect of addition of hydroxyapatite as secondary filler in CNT-reinforced polypropylene hybrid composites

This work entails the effectiveness of hydroxyapatite (HAp) as secondary filler in polypropylene (PP) matrix composites reinforced with HAp-decorated multiwalled carbon nanotubes (MWCNTs). Different composites were prepared through the melt mixing approach. The consequent effect of typical biocompatible ceramic coating on the dispersion of CNTs in a PP matrix and thereby effect on its thermal and mechanical properties have been discussed in this research work. Isothermal hydroxylation technique has been used for the coating of HAp on MWCNTs. It has been observed from the collective information obtained from X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy and field-emission scanning electron microscopy images that HAp constitutes a new phase in the HAp-CNT nanocomposite in the form of a coating of HAp over nanotubes. As a result of which, the use of HAp-coated MWCNTs in PP improved its tensile strength by 38%, modulus of elasticity by 72%, storage modulus by 43% and ductility by around 7.4% in comparison to uncoated MWCNT-reinforced PP composite. However, the coating of HAp shows an insignificant effect for change in temperature-dependent properties of the CNT/PP composites. The improvement in mechanical properties is attributed to the interfacial compatibility between HAp and PP.