This study relates to technology for tailor-making PF resin with molecular weight and size distributions beyond those now available for commercial processing. Consequently, adhesive mobility and cure speed can be adjusted through use of a two-component resin system comprised of continuous and dispersed phases. Current studies specifically concern two-component alkaline plywood formulations suitable for bonding veneer at 12 plus or minus 2% m.c.
The objectives of this study were to produce and modify phenolic dispersion based adhesives using technology recently developed at Forintek and to further characterize the physical properties and bonding properties of these systems for veneer and composite board applications with emphasis on faster cure speed potential. Data developed in this study indicate opportunities to improve waferboard and plywood PF adhesives in terms of color, cure rate and application properties. Further research work is recommended to improve techniques for producing and characterizing appropriate powder disperson-like formulations for wood bonding.
Further data on flow, viscosity-solids and veneer bonding at dry and 11 plus or minus 2% wood m.c. conditions are provided for heated PF powder systems. This information is intended to supplement the main report issued in March 1987.
A series of dispersion-resin plywood formulations were prepared in the laboratory and their bond performance assessed on incised spruce veneer at 10% m.c. Excellent bond quality results were achieved in these laboratory experiments as indicated by high average % wood failure values of over 90%. To further develop the plywood dispersion resin, a pilot plant trial at a gluing company was conducted and again excellent bond quality results were achieved. A large quantity of the plywood dispersion resin was prepared and a successful mill trial at Cantree Plywood was carried out. This trial demonstrated that more dimensionally stable panels can be prepared from high m.c. veneer. The waferboard dispersion technology developed in this study helped facilitate a mill trial using high moisture content face wafers.
The new technologies, incising, moisture tolerant phenolic adhesives and steam pressing were evaluated for the manufacture of laminated veneer lumber (LVL). Both 8- and 13-ply incised spruce LVL panels were prepared using these new technologies. The results showed that both steam pressing and self-generated steam from wet face and back veneers accelerated temperature rise in the innermost glueline of 13-ply incised spruce LVL panels. This would help facilitate faster production rates for LVL manufacture. Bond quality and edge bending values were determined for the steam-pressed 8-ply and 13-ply incised spruce LVL panels. In all cases the average % wood failure was above 90% indicating excellent adhesion between the moisture tolerant adhesive and wood. The modulus of rupture and modulus of elasticity values measured for the steam-pressed incised spruce LVL samples compared very favourably with those for a commercial Norway spruce 15-ply LVL product.