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.
Six impregnating phenol formaldehyde (PF) resins having low to moderate molecular weight were synthesized and evaluated for their wood veneer penetration and curing properties. Based on the results from the penetration and curing properties studies, a PF resin designated as B-2 was used to impregnate subalpine fir, white spruce and lodgepole pine veneer. LVL panels, 12 x 12 inch, were prepared with these veneers. Both modulus of rupture (MOR) and modulus of elasticity (MOE) were increased by 10 to 15% for the resin-impregnated LVL made from each of the SPF species. Edgewise bending results for specimens cut from 2 x 4 foot white spruce LVL panels showed an increase of 15% both for MOR and MOE for the resin impregnated specimens. As well, the dimensional properties (% edge swelling and % water uptake) of the SPF LVL panels were improved by 50% using the patented Forintek resin impregnation method.