Measurement of ”Speed of Set” of Room Temperature Setting Wood Adhesives

A characteristic of interest to the wood adhesive user is its “speed of set.” Several methods have been used to measure speed of set, but they generally involve a visual inspection based upon a short clamp period and a cleavage test. An apparatus employing 1-inch cubes of wood spread with an adhesive is described for testing speed of set of room temperature adhesives. With this system the specimens can be bonded and tested without being moved from the pressure jig. The numerical values obtained are reported in inch pounds of torque and may not be directly related to other systems of measuring bond strength, but do bear a good relationship from one adhesive formulation to another. With this apparatus, the desired surface is spread with adhesive, placed in a square socket, and mated with another cube placed in an opposing socket. An air cylinder is used to apply a calculated amount of pressure for a given period of time. One socket is connected to a lever arm which is activated by an air cylinder applying a torsion force to the glued blocks, the rate of loading being controlled by a gear electric motor which drives the stem of an air pressure regulator.

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