Abstract:

In order to prepare halogen-free flame retardant polyacrylonitrile (PAN) fibers, the vinyl acetate (VAc) unit in P (AN-co-VAc）fiber was selectively hydrolyzed with KOH aqueous solution at different pH values. The phosphorus-containing flame retardant P (AN-co-VAc) fibers were prepared by the phosphorylation reaction of O,O-diethylphosphoryl chloride with the hydrolyzed P (AN-co-VAc) fiber. The structure of P (AN-co-VAc) fibers was characterized by Fourier transform infrared spectroscope, and the thermal properties of the fibers were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The charbon residue of the phosphorus-containing flame retardant P (AN-co-VAc) fiber was analyzed by scanning electron microscope. The results show that the VAc unit is quickly hydrolyzed with the increase of pH. DSC analysis indicat that the presence of VAc increases the temperature of cyclic exothermic peak, and Tp reaches to 287 ℃ with the mass fraction of VAc of 30%, while the temperature of the flame retardant polyacrylonitrile fiber can be up to 340 ℃. TGA demonstrates that the charbon residue of the flame retardant fibers at 800 ℃ is over 48%, which is higher than that of the control fiber (41%),  fully proves that the flame retardant P (AN-co-VAc) fiber has good charon forming capability.

Key words: halogen-free flame retardant polyacrylo nitrile fiber, acrylonitrile, vinyl acetate, hydrolysis, thermal property