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

Abstract

The use of the equation f = km/αE, correlating number of degrees of freedom m of polymer segments between cross-linking nodes in polycondensation networks to the energy of interaction polymer segment/ polymer segment, both within the same polymer and at different polymers interfaces, hence directly 'in situ' in a lignocellulosic joint, through measures of deflection in bending by dynamic thermomechanical analysis, yields a number of consequences of interest in the field of polycondensation hardened networks and of their process of hardening. From this equation, regression equations correlating only two parameters are obtained. The use of these equations allows the easier determination of the parameters which are more difficult or lengthy to obtain by experimental means. The process of networking, hence of the reaction of polycondensation between the gel point and complete hardening of the network, can be followed by the determination of the average number of 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 in particular of the more difficult to follow networking of oligomeric tannin adhesives 'in situ' in the wood joint.