Kinetics of resorcinol–formaldehyde polycondensation by DSC
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The kinetics of resorcinol–formaldehyde polycondensation was investigated by DSC. The resorcinol–formaldehyde polycondensation mixtures were prepared using different catalyst (Na2CO3) concentrations (molar ratio of resorcinol/catalyst R/C = 25 and 50) and mass contents of reactants (w = 20 and 40%). The studied polycondensation mixtures were heated from 10 to 100 °C at five different heating rates (0.5–2.5 °C min−1). The two obtained DSC peaks correspond with two reaction steps (formation of hydroxymethyl derivatives of resorcinol and polycondensation reaction itself). The overall reaction heat evolved during both steps corresponds to 97–104 kJ mol−1 for all mixtures. Based on the kinetic analysis, the first reaction step is best fitted by the second-order kinetic model and its rate is controlled by chemical reaction. The second reaction step can be described by R3 mechanism and is probably limited by diffusion in more viscous solution. Found kinetics equation allows to predict the composition of reaction mixture during the polycondensation at least at micro-scale. The obtained results can be useful for prediction of reaction course which can control the porosity of resorcinol–formaldehyde gels.
KeywordsResorcinol–formaldehyde polycondensation Kinetics Kinetic equation DSC
This work was financially supported by the Ministry of Education, Youth and Sports of the Czech Republic in the “National Feasibility Program I,” Project LO1208 “TEWEP” and by EU structural funding Operational Programme Research and Development for Innovation, Project No. CZ.1.05/2.1.00/19.0388.
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