Gallic acid as a model of tannins in condensation with formaldehyde

In this work, gallic acid (Ga), as a model of hydrolyzable tannins, has been reacted with formaldehyde (F) at different pH values, molar ratios F/Ga, temperatures and for different reaction times. The products obtained from these reactions were analyzed, after acetylation, by size exclusion chromatography (SEC). The kinetic parameters of the gallic acid-formaldehyde condensation have been determined by enthalpic analysis using differential scanning calorimetry (DSC). It appears from these results that gallic acid-formaldehyde condensation depends on the aforementioned preparation conditions. The optimal values of these reactions have been obtained at pH 8, with the molar ratio F/Ga equal to two, for 4 h at 60 degrees C. The results obtained by SEC and enthalpic analysis confirm these conclusions.