How to measure the yellowing resistance of films?

Many paint films will produce yellowing during use and aging, so it is necessary to judge the qualitative change in advance, prevent it and use the paint in a suitable place.

To measure the anti-yellowing performance, firstly, paint the paint on a glass plate with a film thickness of 15 microns. At the same time, make a reference sample with known good anti-yellowing performance. After drying for at least 5 days, carry out the test according to the following method .

(1) In a closed container, put ammonia solution at the bottom, its concentration is 2%~5%, density 0.880, fix the reference sample on the upper part of the container, place the sample plate in the steam generated by ammonia water for 1 ~4 hours, remove and check after leaving in air overnight.

(2) The paint film is aged for 4 days in the air sent from the compressed air storage tank, but the test must be carried out in a closed container at 5o ℃. After the test, compare the sample plate with the reference sample.