Comparison of the kinetics of conventional and microwave methyl methacrylate polymerization

Abstract

A comparative investigation of the conventional and microwaves kinetics of methyl methacrylate (MMA) polymerization was performed. A method for determining the increase of the reaction rate in the microwave field (b) was presented. It was found that at all of the investigated temperatures and powers the polymerization rates increased in the presence of microwave energy by up to 8.9 times compared with conventional polymerization. Isothermal kinetics of the conventional MMA polymerization was investigated and its parameters were determined using isoconversion method. It was found that the calculated kinetics parameters changes complexly with degree of MMA conversion (a) and are in the mutual linear functional relationship, which is so called ''compensation effect.'' The complex changes of the kinetics parameters with a are explained with the postulated model for the mechanism of the MMA polymerization. The kinetics of the MMA polymerization under the microwave field (MWF) with different input power was investigated and its parameters were determined on the basis of the conversion-temperature curves and Arrhenius equation. The values of the kinetics parameters for MMA polymerization in the MWF are dependent on a and are from 1.2 to 12 times lower than that for conventional MMA polymerization. A new method for the determination of activation energy (E a ) of the investigated process in the MWF was described. Decreased E a value of the polymerization process in the MWF compared with the conventional polymerization is explained with the formation of the nonequilibrium energetic distribution of the reactants due to the rapid transfer of energy in the reaction system.

Kinetic Parameters of the Initiator Decomposition in Microwave and in Conventional Batch Reactors – KPS and V50‐Case Studies

“…This can explain why the values estimated for parameters ln( A ) and E are so sensitive to undesired oscillations of the experimental conditions and why different values are frequently reported by different researchers for the same reaction system. For instance, some authors reported the decrease of activation energies in microwave reactions, including the decomposition of KPS, in opposition to the data reported by Raner et al…”

“…This can explain why the values estimated for parameters ln(A) and E are so sensitive to undesired oscillations of the experimental conditions and why different values are frequently reported by different researchers for the same reaction system. For instance, some authors reported the decrease of activation energies in microwave reactions, [31][32][33][34] including the decomposition of KPS, [2] in opposition to the data reported by Raner et al [35] In order to illustrate this point, it was assumed that the activation energy for the KPS decomposition in the microwave reactor was equal to the one obtained in the conventional reactor and the pre-exponential factor was estimated for reactions performed in the microwave reactor. The preexponential factor estimated in this case was equal to ln(A) ¼ 59.921 (A ¼ 1.06 Â 10 26 h À1 ) against ln (A) ¼ 59.166 (A ¼ 4.96 Â 10 25 h À1 ) in the conventional reactor.…”

Recent Advances in Microwave-Assisted Polymer Synthesis

“…[31] In a comparative study with experiments under conventional heating at different temperatures the authors described an acceleration of the reaction rate because of a reduction of the activation energy in polymerizations under MW irradiation. These different polymerization kinetics were attributed to the rapid energy transfer under MW conditions, which was supposed to lead to a non-equilibrium energy distribution in the system.…”

Influence of microwave heating on the polymerization kinetics and application properties of the PMMA dental materials

“…Polymerization of MMA under conventional conditions has been studied comprehensively 19. Conventional and microwave kinetics of MMA polymerization were compared with each other and discussed 20. It was found that at all the investigated temperatures and powers, polymerization rates increased in the presence of microwave energy by up to 8.9 times compared with conventional polymerization 20…”