A study of surface modifications of carbon nanotubes on the properties of polyamide 66/multiwalled carbon nanotube composites

The effects of surface modification of carbon nanotube on the properties of polyamide 66/multiwalled carbon nanotube composites have been investigated. Polyamide 66 (PA66) and multiwalled carbon nanotubes (MWCNTs) composites were prepared by melt mixing. The surfaces of MWCNTs were modified with acid- and amine-groups. Field emission scanning electron microscopy analyses revealed that amine-MWCNTs(D-MWCNTs) dispersed better in the PA66 matrix than pristine- and acid-MWCNTs. However, an introduction of D-MWCNTs into PA66 matrix induced heterogeneous nucleation and affected the crystal growth process during the crystallization of PA66/MWCNTs composites. Both nano-indentation and friction analyses were carried out in a study of the effect of the introduction of modified MWCNTs on both mechanical and friction properties of the composites. With the introduction of D-MWCNTs, both nano-hardness and elastic modulus of the composites were significantly improved but it was observed that the maximum depth, nano-hardness and elastic modulus of the composites showed no distinct change before and after a friction test. It is evident that PA66/D-MWCNTs composites have the least friction coefficient of the PA66/MWCNTs composites of all the approaches of carbon nanotube surface modification.