Preparations And Properties Of Functionalized Carbon Nanotubes/Epoxy Composites

As a type of one-dimensional nano material,carbon nanotubes(CNTs)have hollow and tubular structure,extremely high aspect ratios and surface area,remarkable mechanical,thermal and electrical properties,which can be used as reinforced materials to improve the properties of composites.Nonetheless,ascribed to chemical inertia,CNTs inevitably aggregate and cannot form stronger interaction with polymer matrices.Thus,their poor dispersibility is still the major obstacle to the extension and utilization.Surface functionalization seems to be an effective method to promote dispersion stability and improve the load transfer across the interface of the CNTs and polymer matrices.Functionalized CNTs are incorporated into epoxy and fabricate CNTs/epoxy composites,which combine the advantages of MWCNTs and epoxy,and show high-performance meeting different use requirements.In this paper,Multi-walled carbon nanotubes(MWCNTs)were functionalized by the optimized silanization and the new photo-responsive strategy of π–π stacking and azide-grafting,respectively.The aims of the two functionalization are the improvement of the dispersion of MWCNTs and the enhancement of the interaction of MWCNTs and polymer matrices.Finally,functionalized MWCNTs were individually incorporated into epoxy by the solution blending method and fabricated MWCNTs/epoxy composites.The influences of MWCNTs for the mechanical,thermal and corrosion resistance properties of composites were discussed detailedly.The main results were as follows:(1)Preparation of functionalized MWCNTs by the optimized silanization.MWCNTs were firstly oxidated by an acidic solution(H2SO4/HNO3),then the oxidated MWCNTs were silanized using a silane coupling agent,3-aminopropyltriethoxysilane(KH550).The results of FT-IR and XPS demonstrated the presence of-COOH groups,Si-O-Si groups and Si-OH groups.Raman analysis and FE-SEM images showed that silanized MWCNTs possessed more carboncontaining defects and were less graphitized as compared to the pristine MWCNTs.The dispersion of silanized MWCNTs were improved,which is discerned by UV-vis spectra and optical photographs.Last,the TGA results showed the decomposition of organic groups on funtionalzied MWCNTs at different temperature.(2)Preparation of functionalized MWCNTs by the new photo-responsive strategy of π–π stacking and azide-grafting.MWCNTs were functionalized via standard physisorption,followed by nitrene addition using azido compounds upon ultraviolet activation.The functionalized MWCNTs show excellent dispersibility without raising distinct damage.The results of FT-IR and XPS demonstrated that that organic triazine molecules deposited physically and azido groups have simultaneously formed on the surface with the stimulation of ultraviolet radiation.Raman analysis and TEM images showed that this functionalization maintained more integrity of structure than the oxidated MWCNTs and silanized MWCNTs.From the results of UV-vis spectra and optical photographs,we discerned that the maximum attainable level of dispersibility was achieved after 700 s ultraviolet radiation,which was significantly higher than silanized MWCNTs.(3)The preparations and properties of functionalized carbon nanotubes/epoxy composites.Different functionalized MWCNTs were individually incorporated into epoxy by the solution blending method and fabricated MWCNTs/epoxy composites.At the 0.4 wt.% π–π stacking and azide-grafting functionalized MWCNTs loading,the tensile strength and impact strength of the epoxy composites reached maximum,which were 71.0 MPa and 38.3 kJ/m2,respectively.In addition,the composites including π–π stacking and azide-grafting functionalized MWCNTs also exhibited the enhancement of the thermal conductivity,which reached to 1.31 W/(m·K),corresponding to a increase of 285.3% compared with the neat epoxy.The result of soak test and neutral salt spray test indicated that the addition of MWCNTs not only maintained the corrosion resistance of epoxy,but also can be used as coatings to protect metallic material in serious corrosion environment.