Aqueous slurry free radical terpolymerization of acrylonitrile (AN) with vinyl acetate (VAc) and a constant amount of 2-acrylamido-2-methylpropane sulfunic acid (Amps) using K 2 S 2 O 8 /NaHSO 3 redox initiatior was carried out continuosly in a 15L continuous stirred tank reactor (CSTR) at constant temperature (60 ?C) and atmospheric pressure. A three level response surface method (RSM) based on central composite design (CCD) was used to examine the effect of VAc concentration (wt%) in monomers mixture, bisulfite to persulfate ratio in redox initiator system ( ) and bisulfite to monomers mixture ratio ( ) on the conversion percentage of monomers to polymer, intrinsic viscosity ( ) and sulfur end groups (SEG) of the prepared polymers. Analysis of obtained results via RSM method revealed that the optimum condition of synthesis were: VAc = 9 % wt (in AN+VAc mixture), bisulfite to persulfate ratio = 9.6 and bisulfite to monomers mixture ratio = 0.027. The amounts of conversion percentage of monomers to polymer, intrinsic viscosity and sulfur end groups under optimum conditions were 75 %, 1.38 dl/g and 190 respectively which means that this polymer can satisfy the requirements for acrylic fiber production. Characterization of optimum sample with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), scanning electron microscope(SEM) and X-ray diffraction (XRD) confirmed that this polymer can be used as fiber precursor. Keywords: Terpolymerization ; acrylonitrile ; vinyl acetate ; Amps ; slurry; CSTR
