How to determine the washability of Architectural coatings coating?

How to measure the scrub resistance of architectural coatings?

The scrub resistance of the coating is one of the important technical indicators of the interior and exterior wall coatings of buildings.

The scrub resistance of the coating is measured on a scrub Tester (Scrub Resistance Tester). Scrubbing test machine is an instrument that makes the brush reciprocate linearly on the coating surface of the test sample to scrub it. The brush motion frequency is 37 reciprocating cycles (74 strokes) per minute, and the brush motion height of each stroke is 300mm, and the middle 100mm interval is roughly a uniform motion.

(1) Preparation of washing medium Dissolve washing powder in distilled water to make a 0.5% (by mass) solution, and its pH value is 9.5-10.0. , The scrubbing medium can also be other mediums specified in product standards.

(2) Soaking the brush Before use, immerse the bristles in water at about 20°C to a depth of 12mm, shake off the water vigorously after 30 minutes, and immerse the bristles in the prepared washing medium at a depth of 12mm for 20 minutes. The brush can be used after this treatment. When the bristles are worn down to less than 16mm in length, the brush must be replaced.

(3) Board making and testing: Make boards on asbestos cement boards according to the standard requirements, and dry them for 7 days at (23±2)°C and relative humidity (50±5)%.

Take 3 prepared test panels, put the painted side upwards, and fix them horizontally on the test bench of the scrubbing test machine. Place the pretreated brush on the painted surface of the test panel, and the test panel bears a load of about 450g (the total mass of the brush and the fixture), rubbing the coating back and forth, and dripping at the same time (the speed is about 0.04 drops per second) g) Prepare a good scrubbing medium to keep the scrubbing surface moist. , Depending on the product requirements, after washing to the specified number of times (or until the color of the bottom plate is exposed in the middle 100mm area of ​​the length of the sample), remove the test sample from the testing machine and wash it with tap water. (4) Test panel inspection and result evaluation Under scattered natural light, inspect the coating of the washed mid-length 100mm area of ​​the test panel. Observe whether it is damaged and expose the color of the bottom plate. .

After washing for the specified number of times, if at least 2 of the 3 test panels have no damage to the coating layer and the color of the bottom plate is not exposed, then the scrub resistance is considered to be qualified.