Some effects of the chemical and physical characteristics of powdered phenol-formaldehyde resins on their adhesive performance

Two-ply parallel laminates were prepared from trembling aspen (Populus tremuloides) and white spruce (Picea glauca) using four laboratory-synthesized and four commercially available powdered phenol-formaldehyde adhesives. Wood failure values of samples tested in tension shear indicated an optimum number average molecular weight for the resins at which the cure rate was maximized while adequate penetration for the formation of durable bonds was attained. The anatomy of the two wood species was an important factor in determining how resin flow at the glueline influenced the bond quality. Higher wood moisture contents facilitated better bonding, especially for the highest molecular weight laboratory resin.

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