Research On Friction Properties Of Carbon Nanotubes/Polypropylene Composites

In order to provide polypropylene which had lightweight,antifriction and wear resistance,carbon nanotubes(CNTs)were chosen to improve the friction performance of polypropylene matrix.To improve interface bonding strength of composites,maleic anhydride grafted polypropylene(PPG)was used as compatilizer.Using the double screw extrusion machine and injection machine to prepare carbon nanotubes/polypropylene composites by means of melt blending and extrusion molding.MMS-2A friction and wear testing machine was adopted to test tribological properties of composites.The hardness,impact toughness and interface binding force of composites were tested.The surface states of composites had been studied by FUR.The crystallization behavior of composites had been studied by DSC.The crystal form of composites was tested by XRD.The SEM,parameters of surface roughness and TG were used to study on friction mechanism of composites.The results were shown that friction coefficient of adding CNTs composites were lower than that of pure PP.When the load was 50 N,the dry friction coefficient of pure PP was 0.5698,the friction coefficient of 0.8 wt%CNTs/PP composites decreased by 11.9%.The strength,toughness had been increased by CNTs.The interfacial adhesion between the CNTs and PP was improved by the addition of compatibilizer.The friction coefficient of composites was lower under water lubrication condition,but the wear rate was higher compared with dry friction condition.The wear rate ofPPG/PP composite and 1.0 wt%CNTs/PPG/PP composite under water lubrication condition were 4.6×10-5mm3·N-1 ·m-1 and 4.5×10-5 mm3·N-1·m-1 respectively,increased 178.8%and 176.8%respectively than that of under dry friction condition.The states of dispersion and interface binding of CNTs/PP composites had been improved by the compatibilizer(PPG),the strength and toughness had been also increased.So the wear rate of CNTs/PPG/PP composites were lower than that of CNTs/PP composites.The wear rate of 1.0 wt%CNTs/PPG/PP composite was 2.60×10-5mm3·N-1·m-1,reduced by 22.4%than 1.0 wt%CNTs/PP composite.The crystal type of composites had not been changed by CNTs and compatilizer,so the change of properties were caused by CNTs and compatilizer.The crystallinity of composites was increased with the adding CNTs.Heterogeneous nucleation effect of CNTs had reduced the grain size of composites,the strength and toughness had been enhanced,and friction properties had been improved.The wear resistance of composites could be advanced by CNTs,and wear forms had been changed.When the load was less than 50N,the wear forms of composites were fatigue wear and abrasive wear primarily.Composites appeared adhesive wear when the load was 130N,but the phenomenon of adhesion wear was alleviated after adding CNTs.This was mainly attributed to the strength,toughness and thermal stability of composites had been increased by CNTs.The wear forms of composites was scratches which was caused by ploughing effect under water lubrication condition,because of friction heat had been eliminated,and the abrasive and abrasive dust had been washed away by water.