ABSTRACT
Branched phenol-resorcinol-formaldehyde (PRF) cold-setting adhesives are possibly a new generation of engineered phenol-resorcinol-formaldehyde resins of lower resorcinol content and lower solids content than traditional PRF cold-set adhesives. Thermosetting phenol-formaldehyde resins can be used in place of PRF adhesives during such a crisis, but the cost of equipping a glulam or finger-jointing plant with adequate machinery, such as high temperature, moisture-controlled ovens or high capacity radiofrequency presses, is economically unwarranted. Since resorcinol is such an expensive, strategic chemical, it is also the determining factor in the cost of PRF adhesives. If a chemical molecule capable of extensively branching the phenol-formaldehyde (PF) and PRF resins is used after, before, or during, the preparation of the PF resin, the following are produced: a branched PF and a branched PRF resin and adhesive. The characteristics of branched PRF adhesives are in many respects similar to but in certain others very different from those of traditional PRF adhesives.
