How is paint film adhesion measured?

The adhesion of a paint film can be expressed by the coefficient of friction between the paint film and a non-patterned soft felt moving over it. BnAM proposes two instruments for determining the coefficient of friction: (1) stationary instrument (the test is carried out on the coating film painted on the test panel), and (2) veneer instrument (the test is carried out directly on the surface of the painted object that can be tilted) Carried on). (Related instrument: viscometer)

Stationary instruments (Fig. 81) have movable planes. This plane rotates about an axis, can tilt and change its position to make an angle from 0° to 90° with the ground plane. The inclination angle of the active surface is measured by a goniometer. The entire instrument can be installed in a strictly horizontal position by means of three leveling screws.

When placing the veneer instrument (Fig. 80) on the surface, the angle of inclination of the surface to the horizontal can be determined with the aid of a measuring hammer and protractor. The sliding plate for measuring the coefficient of friction is a flat metal plate with ground edges made of galvanized iron or stainless steel. The size of the board is 30x50x0.5 mm and weighs about 55 grams; the board is covered by a thin felt cloth without twists ( for example, product No. 1039) weighing about 1 gram; the front side of the cloth is facing outwards.

Apply the paint material to be tested to a glass or metal plate. The nature of the painted surface, the method of finishing and drying, and the number of layers of finishing should be selected according to the provisions of the technical conditions. (Related instrument: drying time Tester)

After the time specified in the technical conditions, place the test plate on the movable surface of the fixed device with its unpainted side facing the movable surface, and then place the slide plate on the side with the coating film. (Related instruments: adhesion Tester)

When the inclination angle of the movable plane on which the test plate is placed gradually increases, measure the minimum angle at which the slide plate slides down from the test plate. The coefficient of friction between the paint film and the felt covering the slide can be expressed by the tangent of the above angle.

The coefficient of friction of the surface of the painted object can be measured by means of a veneer instrument. For this reason, the veneer instrument must be placed on the surface and measured according to the inclination between the surface and the horizontal plane measured by the measuring hammer while the slide plate slides down. The following special conversion table (see Table 22) can be used to convert the sliding angle into the coefficient of friction.