Casein is produced by acidifying milk and precipitating out the casein product. Casein has been used for many years as a wood adhesive. Casein glues are naturally gap filling and are satisfactory to use in bondline thickness up to about 0.08 cm.
RESULTING PROPERTIES
The glues have poor resistance to water, chemicals, and mold growth. However, these properties may be improved through the use of additives. Although they cannot be used outdoors, casein adhesives are resistant to dry heat up to 70°C. Resistance to organic solvents is also generally considered to be good.
The formulation above provides for a waterproof casein adhesive by virtue of the addition of urea. It can be used, for example, as a waterproof label for glass bottles.
