Kinetics of foamed polymerization process

Abstract

The kinetics of foamed polymerization of acrylamide were studied for the first time. These studies began with the synthesis and characterization of the starch-g-polyacrylamide and polyacrylamide homopolymer using potassium persulphate as initiator by the foamed polymerization process. The chain scission of the water soluble starch in the presence of alkali foaming agent, Na2CO3, was found in that its molecular weight was reduced. The kinetics of foamed polymerization of acrylamide using potassium persulphate as initiator under the isothermal condition were studied. The acrylamide monomer and potassium persulphate initiator concentrations studied were ranged from 2.44 to 3.66 mol/L and from 1.22x10 -3 to 6.10x10 -3 mol/L, respectively. The studied temperature was ranged from 70 to 90 ํC. The differential scanning calorimetry (DSC) technique was used for the measurement of polymerization kinetics. The dependences of the initial rate of polymerization on monomer and initiator concentrations were found to be raised to 1.21 and 0.50 power, respectively. The rate of polymerization (Rp) is Rp = K[AM]1.21[K2S2O8]0.5. The average overall rate constant at 70 ํC is 5.45x10 -3 L/mol-s. The overall activation energy is 58.4 kJ/mol. The thermal effect of the foamed polymerization of acrylamide under non-isothermal condition was studied. During the course of polymerization, the temperature of the system was allowed to rise exothermically and led to the occurrence of autoacceleration reaction in the system. It was also found that the larger scale of polymer synthesis, the increase in the reaction mass and the lower surface area/volume ratio of reactor enhanced the rise in temperature and autoacceleration reaction in the system. The autoacceleration reaction leads to the higher polymerization rate and the higher monomer conversion to polymer.