Considerations on the interface between lignocellulosic materials and tannin-based and other thermosetting adhesives

The use of the equation f = km/alpha E, correlating number of degrees of fr eedom m of polymer segments between cross-linking nodes in polycondensation networks to the energy of interaction polymer segment/polymer segment, bot h within the same polymer and at different polymers interfaces, hence direc tly 'in situ' in a lignocellulosic joint, through measures of deflection in bending by dynamic thermomechanical analysis, yields a number of consequen ces of interest in the field of polycondensation hardened networks and of t heir process of hardening. From this equation, regression equations correla ting only two parameters are obtained. The use of these equations allows th e easier determination of the parameters which are more difficult or length y to obtain by experimental means. The process of networking, hence of the reaction of polycondensation between the gel point and complete hardening o f the network, can be followed by the determination of the average number o f degrees of freedom m of the polymer segments between cross-linking nodes obtained through these equations. This is all the more useful as it allows the following of the progress of networking of thermosetting adhesive and i n particular of the more difficult to follow networking of oligomeric tanni n adhesives 'in situ' in the wood joint.