Effect of temperature on initial stage of methyl methacrylate free radical bulk polymerization

Abstract

The classic theory of free radical polymerization is based on two assumptions. The first is that the concentration of the initiator is slightly changed and could be taken as a constant value. The second assumption is that the rate of initiation is equal to the rate of termination. The equation for the polymerization rate based on these assumptions cannot successfully describe the initial stage of free radical polymerization. In order to solve this problem, three mathematical models were developed and used to verify the mentioned assumptions. The models were fitted to experimental data and qualities of their fits were compared. Experimental data of isothermal bulk polymerization of methyl methacrylate were obtained by differential scanning calorimetry at 60, 70, 80 and 90 °C with initiator concentration (AIBN) of 0.5 mass%. The best fit was shown by the model that assumes constant concentration of initiator during the initial stage but takes into account that the rate of initiation is not equal to the rate of termination at the beginning.