The relationship of press closing time, strength properties and density profile of thick waferboard panels to mat moisture content was demonstrated in this study. Lower mat moisture contents were found to increase press clothing time but permit faster binder curing. When the distribution of mat moisture was higher in the face layers, shorter press times were achievable and a significant densification of the panel was observed.
Overall properties of poplar waferboard can be considerably upgraded by the massive use of an inexpensive resin binder derived from ammonium-based 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 exising 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.
Aligned waferboard panels were prepared, the mean and the standard deviation of measured angles of aligned face wafers were carefully determined. The importance of orientation angle and angle distribution was demonstrated for board properties such as modulus of rupture and module of elasticity. Linear and non-linear regression models were studied and a number of prediction equations in terms of strength properties were tested and reported.