Polymerization of methyl methacrylate in presence of graphite and silicon

Rates of sodium bisulfite initiated polymerization of methyl methacrylate (MMA) in water medium were determined in absence and in presence of graphite or silicon. The effect of graphite as well as of silicon on the overall rate of polymerization at 40°C was measured. Overall rates of polymerization increased in presence of graphite from 2.3 × 10−5 to 8.7 × 10−5 mol·1−1·s−1 when its concentration was varied from 0 to 5g·l−1, and to 5.6 × 10−5 mol·l−1·s−1 as the silicon concentration was varied from 0 to 16 g·l−1. Beyond these concentrations of graphite and silicon, the overall rate of polymerization began to decrease. The overall rate was found to increase with increase of monomer concentration in case of graphite and in case of silicon with the difference that the increase in case of silicon is limited. Mild shaking was found to increase the rate of polymerization. Raising the temperature from 30°C to 60°C increased the overall rate from 2.6 × 10−5 to 9.3 × 10−5 mol·l−1·s−1 when using a small amount of silicon (3 g·l−1) while the increase was from 3.7 × 10−5 to 11.0 × 10−5 mol·l−1·s−1 when using the same concentration of graphite. Increasing the initiator concentration resulted in a limited increase in the overall rate. The number average molecular weights of the obtained polymers were found to decrease with increase of substance (graphite or silicon).