Strength And Toughness Properties Of Epoxy Composites Reinforced With Jeffamines-grafted Carbon Nanotubes

Carbon Nanotubes (CNTs), referred as its excellent performance and comprehensive application. Recently, CNTs is widely used in industry, the life and the biological application, because of its excellent mechanical, electrical and thermal properties. When the CNTs is joined in epoxy resin, it is used to be an additive to improve mechanical strength of the epoxy resin. Jeffamine is a kind of flexible amine, which molecular structure contains amino (-NH2) and ether (C-O-C-), is widely used in the low temperature curing agent of epoxy resin. Because of flexible groups of the Jeffamine, just like amino and ether, etc, the excellent toughness and impact strength of the epoxy resin, which cured by Jeffamine, could be obtained. However, the strength and modulus of resin matrix may be reduced due to the addition of flexible segments in the crosslinking network. In this paper, CNTs grafted with Jeffamines T403 were used to simultaneously improve the reinforcement and toughening of an epoxy resin. The raw multi-walled carbon nanotubes (r-MWNTs) were functionalized with amine groups according to three steps: carboxylation, acylation and amidation. Through amino functionalization, the amide groups (-CONH2) was grafted on the side wall of MWNTs (f-MWNTs). The f-MWNTs were characterized by Fourier transform infra-red (FTIR), thermogravimetic analysis (TGA), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The experimental results indicated that the T403 was grafted to the surface of MWNTs. The mechanical and thermal properties of epoxy casting and unidirectional composite with f-MWNTs were investigated. With the contents of f-MWNTs increased, the mechanical properties (The tensile strength, flexural strength, impact strength, interlaminar shear strength, bending strength) would increase to maximum at first, and then decreased. And the bending strength of unidirectional composite would increase with the contents of f-MWNTs increase. At the same time, dynamic mechanical thermal analysis (DMTA) showed that the glass transition temperature (Tg) of casting and unidirectional composite with f-MWNTs were increased slightly. Compared with pure epoxy, Tg of epoxy and unidirectional composite with 0.5wt% f-MWNTs were increased from 81℃to 97℃and 93℃. The fracture surface of epoxy with f-MWNTs was observed by scanning electron microscopy (SEM) to understand the dispersion of f-MWNTs in epoxy matrix and interfacial adhesion between f-MWNTs and epoxy matrix. Compared to neat epoxy, the fracture surface of epoxy with f-MWNTs exhibited more obvious 3-dimensional patterns, and the well dispersed f-MWNTs were intimately adhered to the epoxy matrix, which can be attributed to the strong interfacial bonding between f-MWNTs and epoxy resin.