Water resistance is one of the basic properties of coatings. Products are generally tested for cold water resistance (25°C) and heat resistance (boiling), and some varieties are often tested for water absorption. The determination method is as follows:
(1) Cold water resistance test. Use a solution of wax and rosin (1:1) to seal the hard-dried painted sample, and coat a layer of paraffin wax on the back, then immerse half of the painted sample in cold water at a temperature of 25±1°C. Soak for 24 hours (or according to product standards), take out the sample, blot the water drops with filter paper, check for peeling, blistering, loss of gloss, and whitening of the paint film, record the recovery time, and evaluate whether it is qualified or not. If the paint film has peeling, wrinkling, etc., it is unqualified; or it shall be evaluated according to the requirements stipulated in the standard.
(2) Heat resistance (boiling) water test. Hang the paint film sample after the specified drying time vertically in the hot or boiled distilled water at the specified temperature, take it out according to the specified time, and check whether it is qualified or not.
(3) Water absorption test. It refers to the water absorbed by the paint film immersed in water within a certain period of time, expressed by the weight percentage of the paint film.
