Investigation Of Induced Effect Of CNTs To PAN Macromoleculers In PAN/CNTs Composite Fiber

Polyacrylonitrile fiber is a common commercial fiber which has been produced for a long time and regard as the ideal precursor for high performance carbon fiber.By introduceing nanoparticles in to PAN fiber can make them functionalized.Nowadays,CNTs as an ideal reinforcement have been introduced into many polymeric matrixes and the resulting nanocomposite showed an improvement of mechanical properties and electronical properties.In this article,PAN was chose as polymeric matrix and CNTs as reinforcement to prepare PAN/CNTs nanocomposite fiber,the main aim of this is to investigate the induced effect of CNTs to PAN macromoleculers.The main content was as followed:1) In order to improve the dispersion of CNTs and compatibility with polymeric matrix,modification of CNTs was conducted by acid treatment and PAN grafted method.Raman,FTIR,XPS,SEM,TEM and TGA results showed that the acid treatment had introduced carboxyl on the surface of CNTs,with the increase of treated temperature,the intensity of oxidation increase and the raw structure of CNTs were destroied deeply.By changing the carboxyl introduced by acid treatment into acyl and amido,the CNTs can react with comonomer IA,leading to graft of PAN onto CNTs surface,the weight ratio of grafted PAN was nearly 144%and there is a new network structure formed by CNTs and PAN.2) In situ polymerization was used to prepare PAN/acid treated CNTs composite solution and PAN/PAN grafted CNTs composite solution.The rheological result of the composite solution showed that with low content of CNTs,the CNTs act as a plasticzer and the acid treated CNTs are more effective.With the addition of PAN grafted CNTs,the network structure became dominating,increasing theη~*,G' and G" properties,and the elasticity overcome emplastic.The resulting composite also showed an increase of T_g.3) Wet spinning was used to prepare PAN/PAN grafted CNTs composite fiber, the effect of coagulation,pre-stretch and stretch to the structure of composite fiber were investigated.XRD result showed that with the incorporation of CNTs,the crystallization,f~a and d-space of nascent composite fiber increased slightly,SEM results showed CNTs inhibit the diffusion of solvent and water during coagulation,avoiding the formation of large hole in composite nascent fiber;Due to the effect of residual solvent,XRD result showed that the effect of CNTs was weakened,but the pre-stretched composite showed the same reaction to pre-stretch as neat fiber;XRD result showed that with the incorporation of CNTs,the stretch force also act on macromoleculer in composite fiber during stretch directly.The structure of PAN moleculer changed easily in composite fiber and the orientation of crystal was constant but inequipotential along with axial direction.4) The orientation of CNTs in composite fiber was investigated by polarized Raman spectrum,the result showed that CNTs achieved a relatively high orientation during coagulation and with the increase of stretch the orientation of CNTs increase constantly.5) The structure and property of the composite precursor fiber were investigated.With the incorporation of the CNTs,the crystallization,f~a and d-space of composite precursor fiber decreased and the orientation of crystal in composite fiber exhibit inequipotential along with axial direction;At 1 wt% CNTs loading,the tensile modulus and tensile strength increased 82.2%and 11.0%respectively;and the fibril ends were observed at the fracture of composite fiber.