The Research On The Thermal Reaction Rate During The Oxidative Stabilization Of The Electrospun PAN-based Carbonization Fibers

Carbon fibers have the excellent properties of high specific strength.However,the tensile strength of carbon fibers prepared by traditional methods is far lower than the theoretical value.Due to the structural characteristics of traditional carbon fibers,the time of production is long and the cost of that is very high.All of this impact the extensive application of carbon fibers.The PAN fibers prepared by electrospinning method have the characteristics of small size effect,sitallization and homogenization.Electrospun PAN fibers can reduce the generation of various defects during the production from nascent fibers to carbon fibers and these can rapidly achieve the structural transformations through thermal treatment.It is of great significance to rapidly preparing high performance carbon fibers.In this paper,electrospinning equipments and a complete set of self-made dynamic circulating water bath were used to collect the electrospun PAN fibers.The precursor fibers were then obtained through aftertreatment.The possibility of preparing electrospun carbon fibers with shorter stabilization time and higher reaction rate were investigated;The characteristics of the structural evolution with the two kinds of fibers were compared which were of the same component,different order of magnitude diameter and their related structure by means of SEM,FT-IR and XRD;The structure of the final carbon fibers prepared by electrospun method was compared with that of the ordinary carbon fibers through the same treatment by the test methods of Raman spectru and WAXD.Research suggests that:(1)Due to the small size effect and the perfect internal structure of electrospinning fibers,the oxidative stabilization time of 14minutes,16minutes and 18minutes were completed.Compared with the 80minutes stabilization process of SAF fibers,the maximum shortening time is up to 82.5%.And the density and strength of carbon fibers were not lower than that of the best value we ever done whose oxidative stabilization time is 20minutes.(2)The diameter of the precursor fibers prepared by electrospinning is nearly 1/40 of the original SAF fibers.The surface of the electrospun fibers is smoother and there are no obvious defects.The degree of crystallinity and orientation is higher than that of the original SAF fibers.The results showed that the electrospinning method has the advantages of preparing fine diameter and better structure of precursor fibers.(3)The degree of cyclization and the oxygen contents of the electrospun fibers are higher than those of SAF fibers through the same initial stabilization conditions based on the smaller diameter and the higher surface area of electrospun fibers.Finally,the oxygen content of electrospun fibers is higher than that of SAF fibers.The result of XRD tests corroborated the result of DSC tests.The difference between the final degree of cyclization is small,but the cyclization reaction of electrospun fibers is more uniform in each temperature region.(4)The surface of electrospun nanofibers is more smoother,the value of VP is lower,and the density of the final carbon fibers is higher.The results showed that the structure of electrospun fibers is more compact,and the hole defects are fewer.The value of La is larger,and the degree of graphitization is higher.All that research showed the growth of graphite crystallite of electrospun fibers is faster,the degree of aromatic ring structure is higher,and the improvement of the chain structure is more perfect.