POLYCONDENSATION AND AUTOCONDENSATION NETWORKS IN POLYFLAVONOID TANNINS - I - FINAL NETWORKS

A thermomechanical analysis (TMA) study, directly on a bonded joint du ring the process of adhesive hardening, on the sinergy and interferenc e between polycondensation and autocondensation on procyanidin, and pr ofisetinidin-prorobinetinidin-type polyflavonoid tannins network forma tion and hardening, confirmed that also at the higher curing temperatu res characteristic of the hardening of tannin-based wood adhesives, ha rdening by polycondensation can be coupled with simultaneous hardening of tannins by autocondensation. Some coreactants appear to depress th e tannin autocondensation while still leaving a small contribution of this reaction to the formation of the final crosslinked network. Other coreactants instead appear to enhance formation of the final network by sinergy between the 2 condensation mechanisms, while still others d o not show any interference between the 2 types of reaction. (C) 1998 John Wiley & Sons, Inc.