Effects of hyperbranched polyesters covalent functionalized multi-walled carbon nanotubes on the mechanical and tribological properties of epoxy composites

Abstract

In order to improve the mechanical and tribological properties of epoxy composites, the hyperbranched polyesters with terminal carboxyl (HBP) were used for covalent functionalization of multi-walled carbon nanotubes (MWCNTs). The dispersibility and wettability of functionalized MWCNTs (HBP-NH _2 -MWCNTs) in epoxy resin (EP) were analyzed. The HBP-NH _2 -MWCNTs reinforced EP composites (HBP-NH _2 -MWCNTs/EP) were prepared. The microhardness and fracture toughness of HBP-NH _2 -MWCNTs/EP were tested, and the tribological behavior and mechanism under dry friction conditions were investigated. The results show that the hyperbranched polyesters coated on the surface of MWCNTs forms a physical barrier layer, blocking the van der Waals force between MWCNTs, effectively reducing the agglomeration phenomenon and significantly improving its dispersibility and wettability. Meanwhile, The flexible hyperbranched polyester on the surface of MWCNTs alleviates the stress concentration of the interface and improves the load transfer efficiency, which greatly improves the microhardness and fracture toughness. Under dry friction conditions, the friction coefficient and wear loss of HBP-NH _2 -MWCNTs/EP composites showed a trend of decreasing first and then increasing as the content of HBP-NH _2 -MWCNTs increased from 0.3 phr to 1.2 phr. When the content of HBP-NH _2 -MWCNT is 0.6 phr, the composites has the lowest friction coefficient and the wear loss, and the wear mechanism is mainly characterized by slight fatigue wear.

Keywords

• hyperbranched polyesters
• MWCNTs
• tribological properties
• composites
• epoxy resin