Plywood Adhesives–Developments and Trends

The increasing use of phenol-formaldehyde resins has been made possible by three important subtrends: 1) Their steadily decreasing glueline cost, 2) their steadily decreasing basic press time requirement, and 3) their increasing versatility. In terms of productive capacity, 20-opening hot press can now provide the same production capacity as a 25-or 28-opening press would have provided in 1955. Many of the new instruments and analytical techniques presently being used to study phenolic resins are the result of major breakthroughs in electronics. Nuclear magnetic resonance equipment can now be purchased for $20,000; differential thermal analysis equipment for $10,000. Gel permeation chromatography is reported to be adapted to water soluble phenol-formaldehyde resins. A few needs for the future are a faster-curing fully-durable adhesive system, also adhesives which will permit the bonding of species other than Douglas-fir under the same conditions of spread, assembly time, and press time as are used with Douglas-fir. Wider use of automation in plywood mills is introducing new. adhesive requirements. There is interest in methods of applying adhesives other than by roller-type spreaders. Techniques such as spray systems, air knife glue respreaders, flow coaters, and dips are of interest.

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