Kinetics of thermal-initiated free radical copolymerization of styrene and methyl methacrylate

Abstract

The kinetics of thermal-initiated of homopolymerization of styrene and methyl methacrylate (MMA) using 2,2 ́-azobisisobutyronitrile (AIBN) as initiator were studied. Differential scanning calorimetry (DSC) technique was employed to detect the heat evolved during the polymerization which was used to calculate the monomer conversion at particular time. The reaction order of polymerization of styrene and MMA at 80๐C with respect to the initiator concentration was 0.33 and 0.53, respectively. The activation energy of the polymerization of styrene and MMA was 85.0 and 83.6 kJ/mol, respectively. The frequency factor of the polymerization of styrene and MMA was 2.84x10⁹ and 4.88x10⁹ L[superscript 1/2]mol[superscript -1/2]s⁻¹, respectively. The kinetics of copolymerization of styrene and MMA were studied at 60๐C with the variation of feed monomer composition in the ranges of 0.2-0.6 mole fraction of styrene. The value of kp of the copolymerization using the comonomer having 0.2, 0.4 and 0.6 mole fraction of styrene were 689, 625, 498 L-mol⁻¹s⁻¹, respectively. The reactivity ratio of styrene and MMA was in the range of 0.40-0.48 and 0.08-0.50. Gas chromatography was employed to confirm the DSC technique. The data from both techniques were not much different. The relative error of two methods was in the ranges of 0.01-3.58% and 2.24-9.10% for homopolymerization and copolymerization, respectively.