Preparation And Properties Of Carbon Nanotubes / Basalt Fiber Multiscale Composite

Basalt fiber is made from natural volcanic rock ore.It is a new kind of mineral fiber made by melting and drawing at 1400?-1500? after the ore is completely broken.Basalt fiber has high strength and modulus with simple processing,low cost,excellent temperature resistance and corrosion resistance,outstanding chemical stability,anti-ultraviolet ability and high-energy electromagnetic radiation,as well as good flame retardance.Therefore,it is considered as a green industrial material and an ideal choice for the producing advanced composite materials.Although the composition of basalt fiber is similar to that of glass fiber,the properties of basalt fiber are much better than that of E-type glass fiber.The surface of basalt fiber is smooth,the interaction between basalt fiber and matrix is weak,and the interface bonding strength is low.It is easy to pull out,break and debond when subjected to large external load.In addition,its thermal radiation coefficient is high,the resistivity is big,and the wear resistance is poor,which affects the application of basalt fiber to some extent.In order to meet the requirement of application performance,modification is needed to improve the interface bonding strength and achieve multi-functionality.By adding nano-sized carbon nanotubes into the basalt fiber/ vinyl ester resin composite system,the interfacial properties can be significantly improved by composite effect,multi-scale effect and interface effect,the thermal properties,electrical properties and friction resistance of the materials can be improved,and the high performance and multi-function of the multi-scale basalt fiber reinforced composites can be realized.It is in line with the current trend of the development of advanced composite materials.In this paper,carbon nanotubes are first functionalized and then introduced into composite materials.The property of carbon nanotubes was modified with carboxylated carbon nanotubes and coupling agents on the surface of basalt fibers and vinyl ester resin matrix.When the carbon nanotubes were grafted onto the surface of the micron-sized basalt fibers,the multi-sized reinforcements had more reactive active points of carbon nanotubes,and the surface roughness was increased.The increased interfacial roughness is more favorable for the contact between polymer molecules and basalt fiber surface,so as to enhance the surface property of basalt fiber,to improve the impregnation between basalt fiber and resin,to increase the cross-linking degree of resin near the surface of fiber,to construct a gradient interface between basalt fiber and matrix,and to help the dispersion of interfacial stress.The carbon nanotubes added to the matrix of basalt fibers can form a mechanical tooth-like wedge shape which limits the movement of resin molecules on the surface of basalt fibers to a certain extent,thus preventing cracks in the interface region.The carboxylated carbon nanotubes COOH-MCNTs,the coupled carboxylated carbon nanotubes KH550-MWCNTs,and the KH570-MWCNTs are respectively formulated into a sizing agent with an ethanol/water solution,and applied to the surface of basalt fiber and basalt fiber clothes.The surface physico-chemical properties were tested based on electron microscopy and X-ray.The results showed that the surface roughness and surface energy were significantly improved after sizing,and the infiltration was also improved.Interfacial shear strength,flexural strength,impact strength and thermal properties of basalt fiber reinforced rod composites are tested.Furthermore,bending strength,impact strength,type II interlaminar fracture toughness of fiber reinforced laminated composites(made by VARTM),the inter-shear strength,electrical properties,thermal properties and wear properties were also analyzed and analyzed.Meanwhile,the SEM morphology of the fractures was observed.The effects of sizing agent modification on different types of carbon nanotubes were discussed based on the obtained results.The results show that the interfacial shear strength,tensile strength,bending strength and impact strength are greatly improved by the addition of different kinds of carbon nanotubes in the multi-scale composites of basalt fiber grafting pultrusion carbon nanotubes.And the highest value can be obtained at three times of KH550-MWCNTs coating,which is increased by 101%,18.3%,25.7% and 45% respectively.The thermal stability of composites is improved and the char yield at high temperature is pretty high.The thermal expansion coefficient is decreased,which of composite material KH550-MWCNTs/BF/VE is decreased by 66.7% under vitrification transition temperature and decreased by 13.6% when above that.Mix and add COOH-MWCNTs and KH570-MWCNTs into BF/ VE composites and add COOHMWCNTs into matrix.The bending strength is increased by 25.1% and the impact strength is increased by 27.4%,while the bending strength of KH570-MWCNTs system is increased by 28.4% and the impact strength of that is increased by 42.5%.Analyze the morphology,surface elements and functional groups of the modified multi-scale reinforcements of basalt fiber cloth and carbon nanotubes.The results show that the number of active organic groups is increased when the surface of basalt fiber cloth is processed by carbon nanotubes.The bending strength,impact strength,fracture toughness of type II interlaminar and interlayer shear strength of the composites are all increased in a large degree by adopting the multi-scale composites grafting pultrusion carbon nanotubes of VARTM process.The vitrification transition temperature can be increased by 4.4? in the highest degree and the tangent angle of loss is decreased.The thermal stability at high temperature is increased.The resistivity is decreased by 8-10 orders of magnitude.The friction performance is improved greatly and the rub performance and abrasion resistance of multi-scale composite system are the best when the content of KH550H-MWCNTs is 0.1%.