Research Of Liquid Modification On Pan Based Carbon Fibers’ Precursor

As a new type of national strategic materials,high-performance carbon fiber has significant advantages in terms of excellent performance of mechanics and thermology.It was explored for the application in the field of national defense firstly,and now it has been in widespread use in various national economic fields.However,high production costs become one of the main factors restricting the development of carbon fiber.Therefore,the research about low-cost carbon fiber has already been the task of top priority.The main factors that influenced the cost of carbon fiber are the price of precursor fiber,the new process of pre-oxidation and carbonization,as well as the corresponding equipment costs.The process of thermal stabilization is important and functions as an indispensable bridge,but it takes a long time to finish the thermal stabilization.Moreover,the carbonization and graphitization process are the main stages of formation of carbon fiber and need to be conducted under inert gas,which lead to the high cost of carbon fiber.Therefore,improving the oxidation rate is an efficient method to reduce cost.If the oxidation speed is too high,the cyclic heat would cause the PAN precursor fiber overheating,and then the fiber is suffered dissociation and fusing.Therefore,improving the oxidation rate is an efficient method to reduce cost.Chemical modification can not only speed up the process of pre-oxidation,reduce the cyclization temperature and the cost,but also enhance the mechanical property of carbon fiber.A novel technology of manufacturing low-cost carbon fiber was reported in this paper.By chemical modification of spinning dope,the PAN was partly cyelized which can reduce the cyclic thermal during the oxidation process.As a result,the speed of oxidation was accelerated while the cost of carbon fiber came down.In this paper,the reaction conditions of PAN spinning solution in liquid phase and the control of cyclization degree were studied firstly.Then the relations of cyclization degree and the cyclic thermal of precursor fiber,as well as the solidification performance,rheology and spinnability of PAN spinning solution with partly cyelized was measured.Finally,the spinning process and the fiber,s performance were explored.The main results included four parts as follows:l,Cyclization reaction in liquid phase:PAN was heated in the PAN/DMSO solution under inert gas.It was found that the heat treatment could give rise to the cyclization in PAN.A new peak at 1669cm-1 in the FTIR spectra and the peak at 414nm-1 in the UV-vis spectra revealed the occurrence of cyclization.The DSC results showed that the heat treated PAN released less heat during the thermal stabilization.Moreover,the heat treatment could also enhance the stability of PAN in the stabilization process and had a higher carbon yield.It suggested that the heat treatment in the solution could induce the cyclization of the PAN and made the stabi ization of PAN easier to occur.2,Solidification and phase picture of part.cydization PAN:By using cloud Point titration and cooling cloud point methods,the cloud point data for PAN-DMSO-H2O system with low concentration were determined.According to the Boom’s linear cloud point curve(LCP),the whole experimental binodal curve was completed by using extrapolation method.Research found that in the PAN-DMSO-H2O system,with the increase of temperature,the binodal move to the axis of PAN-H2O,and the homogeneous area increased with the increase of temperature.It showed that the ternary system at high temperature has a better eompatibility.We also found that after cyclization reaction,the single-phase composed of the three compounds became smaller in the PAN-DMSO-H2O system.3,Rheology and Spinnable of part-cyclization PAN:Through the study of rheological and spinning performance of the modified PAN,we found that the PAN-DMSO after reaction had a higher apparent viscosity than the unmodified of PAN due to molecular structure changes.Like the unmodified PAN,dynamic viscosity of modified PAN-DMSO decreased with the increase of the angular frequency,while the energy storage modulus and loss modulus increased gradually with the increase of the angular frequency.It was also demonstrated that after reaction the PAN-DMSO gelled more easily.Due to the crosslinking in the reaction a high temperature of spinning dope was needed to acquire better raw fiber.And at a high modified temperature the crosshnking level became too high to spin.4,Spinning of part-cyclization PAN:The modified PAN was used for wet spinning.After the spinning conditions was optimized,we found that the mechanical property of the PAN after reaction was higher than the unmodified fiber.Hence the PAN after heat treatment,could produce the high quality of precursor,and the precursor may be more suitable for the manufacture of carbon fiber.In conclusion,PAN fiber prepared by liquid phase cyclization reaction method had an excellent structure and outstanding properties.Consequently,it is expected to manufacture low-cost carbon fiber with high performance using this PAN fiber as the precursor.