Renewable wood adhesives based on cross- linkable protein
Pages: 12 - 16
Hendrikus W. G. van Herwijnen,
Proteins have been used as binders for wood since prehistoric times. In the 20th century they were gradually replaced by “pure chemical” binders. These superior new binders also allowed the large scale production of new wood composites like particle- and fibreboards. Because of the awareness that chemical binders are based on limited fossil resources and because of environmental concerns, proteins made a comeback. Nowadays, effective hybrid systems of proteins with for example phenolic or PAE (polyamido-amine-epichlorohydrin) resins exist. “Full protein” systems, however, still suffer under disadvantages such as inferior moisture resistance and slow reaction. One reason for this poor behaviour is the lack of crosslinks in an unmodified protein system. In order to turn these systems into crosslinkable resins, enzymes can be used. Transglutaminase, for example, links glutamine to lysine, both amino acids readily present in many proteins. Using DNA technology, the enzymes can be adapted to the preferred reaction conditions for the envisioned application, such as the temperature. Furthermore, also the enzyme activity can be increased. The suitability of proteinous resins that are cross-linkable by enzymes was demonstrated by the production of laboratory particleboards.