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J. Szafko, K. Onderko, B. Pabin-Szafko

Thermal decomposition of 2,2'-azobis(2-methyl-4-hydroxybutyl) propionate

in the N,N-dimethylformamide/methyl methacrylate system (in English)

Polimery 2003, No 5, 329


DOI: dx.doi.org/10.14314/polimery.2003.329


Summary

The thermal decomposition of the initiator 2,2?-azobis(2-methyl-4-hydroxybutyl)propionate (AIB-BD) at 333 K in N,N-dimethylformamide (DMF), methyl methacrylate (MMA) and various DMF/MMA mixtures was studied by volumetric method. The values of the stationary rate AIB-BD of decomposition for various initial concentrations of the initiator [I]0 (within the range of 0.067-0.132 mol · dm-3) were determined according to differential eq. (7). These values, according to eq. (8), allowed to determinate the order (x) of initiator decomposition reaction [defined in eqs. (2) and (4)]. The order x can be regarded as equal to 1 for the whole system, i.e., from a pure solvent (DMF) to pure monomer (MMA). The presented method of determination of the order x cannot be replaced by the estimation of linearity of eq. (10) what is frequently used in the publications, since the other kinetic dependences are also linear for x = 1 and x = 2. The thermal decomposition rate constant (kd) of AIB-BD is equal 5.19 · 10-4 min-1 and 4.12 · 10-4 min-1 in pure DMF and MMA, respectively. The kd values concerning DMF/MMA mixtures were found to be dependent on the mixture composition. This dependence is represented by a monotonically decreasing function of the monomer mole fraction (xM). The relation kd = f(xM) has been interpreted on the basis of a model of initiator solvation by monomer MMA and solvent DMF [eqs. (11) and (12)]. The results obtained for the DMF/MMA/AIB-BD system were compared with (previously studied) DMF/MMA/AIBN system.


Keywords: methyl methacrylate radical polymerization, azo-initiators thermal decomposition, order of decomposition reaction, thermal decomposition rate constant, initiator solvation


J. Szafko, K. Onderko, B. Pabin-Szafko

Thermal decomposition of 2,2'-azobis(2-methyl-4-hydroxybutyl) propionate in the N,N-dimethylformamide/methyl methacrylate system (in English)