HYBRID POLYPROPYLENE COMPOSITES: EFFECT OF TYPICAL COATINGS ON MULTI-WALLED CARBON NANOTUBES

Abstract

This work entails the effectiveness of specific coating materials as secondary filler in polypropylene (PP) matrix composites reinforced surface-modified multiwalled carbon nanotubes (MWCNTs). Herein, the coating of zirconia and Hydroxyapatite (HAp) are compared to analyze the effect on mechanical and thermal properties of the composites. The isothermal hydroxylation technique has been used for the coating of zirconia and HAp on MWCNTs. The successful coating of these materials has been confirmed through typical microstructural and morphological characterizations. It has been observed from the collective information obtained from XRD, FTIR, Raman spectroscopy and FESEM images that both the coating materials constitutes a new phase in the modified-MWCNTs nanocomposite in the form of a typical coating of over nanotubes. The composites were prepared through the melt mixing approach using an internal mixer and compression moulding machine. The effect of zirconia on the mechanical and thermal properties of PP matrix composites has been studied by comparing the thermal decomposition behaviour, tensile and thermomechanical properties of pure PP, MWCNTs reinforced PP composite and ZrO2-CNT reinforced PP hybrid composite. In short, the addition of 5 wt% CNTs improved tensile strength by 16%, tensile modulus by 22% and storage modulus by 45%, while the addition of the same amount of ZrO2-CNT improved the above sequenced properties by 44%, 47% and 73%, respectively. Moreover, ZrO2-CNT/PP hybrid composite has been found to have better thermally stability than pure PP and CNT/PP composite. The consequent effect of typical biocompatible ceramic coating shows that 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 MWCNTs reinforced PP composite. However, the coating of HAp shows an insignificant effect for change in temperature-dependent properties of the CNT-PP composites. The superior improvement in mechanical properties due to the coating of HAp is attributed to the interfacial compatibility between HAp and PP.