How to measure the water resistance of film?

Water resistance is one of the basic properties of coatings. Products generally have to be tested for cold water resistance (25°C) and heat resistance (boiling), and some varieties are often tested for water absorption. The measurement method is as follows two

(1) Cold water resistance test

Use a solution of wax and rosin (1 : 1) to seal the edges of 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 the product standard), take out the sample, blot the water drops with filter paper, check whether there is any phenomenon of paint film drop, foaming or loss of gloss, whitening, etc., 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 into 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 in weight percentage of the paint film.