Evidence of chemical reactions between di- and poly-glycidyl ether resins and tannins isolated from Pinus radiata D. Don bark

This work evaluates the feasibility of reacting tannins isolated from Pinus radiata D. Don bark with epoxide resins of the diglycidyl and polyglycidyl ether type. To this end, gel times of aqueous tannin dispersions (40% w/w) with every one of nine selected resins (5% w/w), at previously established pH values (initial equal to 3.3, 4, 7 and 10), have been determined. Products of these reactions were analyzed by FT-IR spectroscopy, and the results were compared with those obtained from tannin-p-formaldehyde and (+)-catechin-p-formaldehyde systems, at the same pH values. Their mechanical properties were evaluated, by dynamic mechanical analysis, at two pH values (3.3 and 10). In general, it was concluded that tannin-epoxide resin systems behave similarly to tannin-paraformaldehyde systems, especially at basic pH values.