Ionic Liquid Modification Of Carbon Fiber Surface And Its Effect On The Interfacial Properties Of Composites

It's well known that the composites are multiphase materials formed by reinforcement and matrix.There will be a discontinuous interface layer between the two phases.The structure and properties of interface layer play an important role in the performance of composite.However,the chemical inertness and hydrophobicity of carbon fiber will lead to the poor interfacial adhesion between carbon fiber and matrix.Therefore,there is an effective method for the enhancement of the performance of carbon fiber reinforced composite by modifying the surface of carbon fiber to build a better interfacial structure.In order to improve the interfacial properties of carbon fiber reinforced composite,the ionic liquid was grafted to the surface of carbon fiber by electrochemical method in this thesis.The preparation route for the grafting of ionic liquid on the carbon fiber was established by comparing two different grafting methods.On the basis of the electrochemical grafting route,the grafting mechanism of ionic liquid and process was investigated.Then its influence on the structure of carbon fiber was studied by changing the ionic liquid grafting conditions.Finally,the influence on the interfacial properties of composite was investigated after grafting ionic liquid on the surface of carbon fiber.The result indicated that(1)The ionic liquid was successfully grafted on the surface of carbon fiber by tradition chemical and electrochemical methods.The electrochemical grafting method was established finally by evaluating the influence on physical and chemical structure of carbon fiber after grafting.(2)Based on the experimental result of XPS?SEM and other related data,the mechanism of the grafting of ionic liquid was deduced.At the beginning of grafting reaction,the positive charged imidazole of ionic liquid would cover the surface of carbon fiber by electrical force.At this time,a part of ionic liquid would receive the electron to form radical and carbene,while some others would be grafted onto the surface of carbon fiber with the amide reaction.Then,the grafted ionic liquid would be transformed to carbene under the addition of electron.The formed carbene was continued to react with other radical to generate the ionic liquid polymer on the surface of carbon fiber.(3)The carbon fiber under different grafting condition was analyzed by SEM?XPS and other characterization method.The results indicated that the increase of concentration of ionic liquid would improve the grafting reaction between carbon fiber and ionic liquid.While the excess concentration of ionic liquid would lead to the reduction of grafting polymer due to the radical cage effect.The effect of the current density on the grafting has similar tendency to that of the concentration of ionic liquid.(4)Based on the evaluating of the interfacial shear strength of the composites,the suitable concentration of ionic liquid and current density was chosen.That is,the concentration of ionic liquid is 5%,and the current density is 25 A*m-2,as well as the reaction time of 120 min.In this condition,the surficial property of carbon fiber reinforced composite was improved from 42.27 MPa to 95.52 MPa.