ABSTRACT
This chapter addresses three of the most widely used families of protein-based adhesives for wood; namely, soybean, blood, and casein. The technology of soybean glues will be discussed first because soybean flour is frequently combined with blood or casein to yield adhesives of intermediate properties. During recent decades, mainly since World War II, several different adhesive polymers based on synthetic organic chemicals were developed and quickly preempted entire segments of the wood products industry from protein adhesives. In spite of this intense competition from the new synthetics, protein adhesives maintained a strong position in bonding wood products for interior applications until about 1960. Blends of soybean flour with ground and screened casein also yield a very useful series of protein adhesives; in this case, mostly cured cold. As a special performance property, the bonds of soybean-casein door glues maintain strong adhesion in a fire until the glue lines are literally charred away.
