Lignocellulosic substrates influence on TTT and CHT curing diagrams of polycondensation resins

Lignocellulosic substrates such as wood were found to have a marked modifyi ng in fluence on a well-defined region of CHT diagrams during hardening of phenol-formaldehyde (PF) and urea-formaldehyde (UF) polycondensates. This w as ascribed to more complex resin phase transitions due to resin/substrate interactions peculiar to these substrates. The chemical and physical mechan isms of the interactions of the resin and substrate causing such CHT diagra m modifications are presented and discussed. The Di Benedetto equation desc ribing the glass transition temperature T-g of the system as a function of the resin degree of conversion p has been slightly modified to take into ac count the modified CHT diagram. The modified CHT diagram can be used to goo d effect to describe the behavior of polycondensation resins when used as w ood adhesives during their curing directly into the wood joint. (C) 1999 Jo hn Wiley & Sons, Inc.