MODELING OF TANNINS AS ADHESIVES .1. CONDENSATION OF THE (+)-CATECHIN WITH FORMALDEHYDE

In this work, the (+)-catechin (C), as model of condensed tannins, has been reached with formaldehyde (F) under different pH conditions and varying molar ratios F/C, temperature and reaction time. The products obtained from these reactions were analysed, after acetylation, by Size Exclusion Chromatography (SEC) and the Nuclear Magnetic Resonance (NMR) techniques. The kinetic parameters of these products have been determined by enthalpic analysis on a Differential Scanning Calorimeter (DSC). It appears from these results that (+)-catechin-formaldehyde condensation depends on the preparation conditions. The optimal values of these reactions has been obtained as between pH of 7 and 8 with the molar ratio F/C equal to 1 with a 3 hour reaction time at 85-degrees-C. The results obtained by SEC and enthalpic analysis are at the origin of these conclusions.