Waferboards were made from 5 and 9 year old hybrid poplars, using laboratory prepared wafers. The binder was a powder consisting of a mixture of phenol-formaldehyde (PF) resin and comminuted hybrid poplar bark in equal weights. Only 1.25% PF resin was used based on weight of dry wood. These boards had bending strength and internal bond strength much in excess of the minimum required by Canadian Standards. Another binder was used composed of white spruce tannin, hybrid poplar bark and PF. This amount of PF based on dry wood was 0.5%. this mixture also gave strong boards, both dry and wet, at densities of 42 pounds per cubic foot.
Overall properties of poplar waferboard can be considerably upgraded by the massive use of an inexpensive resin binder derived form ammonium-based spent sulphite liquor (SSL). Further improvement on waferboard quality can be achieved by the combination of higher resin content and thinner wafers. Low-density waferboard also can be produced to meet CSA 0188 requirements by using aligned wafers. This inexpensive SSL binder, however, requires a longer press time and prefers a higher platen temperature to cure. A new waferboard plant, designed and built to fully exploit both technical and economical advantages of this binder system, would be ideal. For some existing waferboard plants it may be necessary to slightly modify their production line in order to adopt this new binder system. Great savings on resin cost can be realized by substituting the expensive petrochemical-based phenolic resin with the renewable and inexpensive sulphite liquor binder. Economically and technically speaking it is entirely possible to produce a new type of better waferboard at a lower cost.