Study On Ramie Fiber Surface Modification Through Carbon Nanotube Grafting

Fiber reinforced polymer composite(FRP)with many advantages,namely light weight,high strength,corrosion resistance,has been widely applied in strengthening of engineering structures,bridge cables and construction of various high performance structures.Compared with traditional fiber reinforcements,ramie fiber possesses low energy consumption,good mechanical performance and pollution-free characteristics.It can be used as a new type of fiber reinforcements for composite materials.However,due to the weak bond between ramie fiber and resin matrix,the mechanical properties of ramie fiber reinforced composite materials are relatively lower.In view of this,to improve the mechanical properties of ramie fiber reinforced composites by fiber surface modification has become an important topic.The present paper proposes a simple and efficient method to modify the ramie fiber surface through spraying of Carbon nanotube(CNT).A CNT ethanol-water suspension was explored,in which the CNT was stably and uniformly dispersed inside.The effect of CNT dispersion in the suspension on distribution of CNT on the ramie fiber surface was studied.The CNT grafting parameters were optimized.The mechanism of CNT grafting on the ramie fiber surface were investigated.The effects of CNT grafting on the the fiber-resin bonding and related mechanisms were studied.The present research contents and conclusions are given as follows:Firstly,the effect of CNT surface modification on the dispersibility of CNT in an ethanol-water solution was studied.It was found that the surface coating of polyvinylpyrrolidone on CNTs and silane coupling agent effectively improve the stability and uniformity of the CNT dispersion in the suspension.Secondly,the paper proposed a simple and efficient spraying method,with which CNT can be uniformly grafted onto the ramie fiber surfaces.The spraying process parameters was optimized to the influence of the ramie fiber surface distribution CNT is studied in ramie fiber grafted on the surface of the mechanism.It is found that the uniform grafting of CNT on the surface obtain the grafting results..Through this method,CNT is covalently grafted onto ramie fiber surfaces,in assistance with molecular bridging effects of silane coupling agent.Finally,the effect of CNT grafting on the interfacial shear strength of the ramie fiber and epoxy resin was studied.The mechanism of the enhancement of the bonding strength was analyzed.The results showed that the interfacial shear strength,,three point bending properties of the composite were improved effectively due to CNT grafting.The improved fiber surface roughness promoted the mechanical friction between the fiber and resin matrix,which is believed to bring in the enhancement of the interface bonding performance.The present study proposed a simple and efficient method to modify plant fibers through CNT grafting,,benefiting the development of high performance natural fiber composite.The study will also promote the engineering application of high performance natural fiber composites.