The Preparation And The Structure-Property Relation Of PAN Precursor Modified By Attapulgite

Carbon fibers, well known for their high tensile strength andmodulus and lightweight, have got great development in recent decades. Among the precursors available for producing carbon fibers, polyacrylonitrile (PAN) fibers are the most commonly used and promising precursors. Now, it is popularly accepted that the quality of high-performance carbon fibers depends mainly on the composition and quality of the precursor fibers. In this thesis, PAN precursor was modified by attapulgite (AT) to improve its mechanical property. The work is summarized as following:1. PAN/AT composites were obtained by means of solution blend technology. The images of scanning electron microscope (SEM) showed the uniform dispersion of AT in the PAN matrix. The test of dynamic mechanical analysis (DMA) indicated that the enhancement of storage modulus resulted from the AT in the PAN matrix. It was found PAN/AT nanocomposites showed much higher tensile strength than that of pure PAN.2. Using dimethylsulfoxide(DMSO) as solvent and by wet-spinning technology, PAN precursors were prepared. The effect of AT on therheological behavior of PAN spinning solution was studied. The effect of temperature and the content of AT on the flowing behavior of the spinning solution was discussed. Increase of AT content will decrease the viscosity of PAN spinning solution and structural viscosity index (△η), while increase the non-Newtonian index (n) and the viscous flow activation energy (Eη). The investigation of dynamic rheological behavior also showed that the addition of AT reduced the viscosity of spinning solution. Under the same conditions, the reduced viscosity is effective ways to improve the quality of precursor. The thermal properties were investigated by thermal gravimetry analysis (TGA). The result indicated that the existence of the AT had little effect on thermal decomposition properties of the precursor. The results of the sonic orientation test proved that the modified precursor have higher orientation. X-ray diffraction(XRD) test showed that the modified precursors had higher the degree of crystallization and smaller crystalline size.. Mechanical tests showed modified precursor much higher tensile strength.3. As evidenced by the SEM observations, AT exhibit good dispersion in the oxided fibers matrix and carbon fibers matrix. The tensile strength of oxided fibers and carbon fibers can be increased by the addition of AT, while the addition of AT in PAN matrix has no effect on the preoxidation and carbonization process of PAN precursor.