Several methods for determination of film water swelling and water resistance

The determination of the swelling property of the paint film can be carried out on the base plate (metal, wood surface) or on a clean paint film. In the latter case, try stripping the paint film. As pointed out in Test 24, the use of cigarette paper-coated paint films for the determination of swelling is a very convenient and useful method; for this purpose, the use of cellophane has also been proposed.

Determination of Water Swellability of Fast Film by OCT Standard Method (OCT10086-39 Test Method 32)

The water-swellability of paint films can be determined according to this method as follows. Coat the iron plate (90x120 mm in size, made of black iron or pickled white iron) weighed on the analytical balance in advance with two layers of the paint material to be tested, and the drying time between the two layers is specified in the technical conditions. (Related instrument: drying time Tester) After drying, weigh the iron plate coated with the film, and then coat it with paraffin wax on its side. To this end, within a few seconds, the four sides of the iron plate are sequentially immersed in paraffinized paraffin at a distance of 5 cm from the other side. After the paraffin solidifies (in 3~5 minutes of gold), weigh the iron plate again, and then immerse the entire surface vertically in a distilled water (20°0±2°C) Water Bath (relevant instrument: constant temperature Water Tank). After a certain period of time stipulated by the technical conditions, take out the iron plate and carefully place it in a dry well between filter papers and weigh it immediately.

The maximum growth of most paint films tends to occur during the first day and night.

While weighing the test panel, it is also necessary to record the changes in the appearance of the paint film: such as loss of gloss, whitening, super foaming, falling and so on. The data obtained can indicate the water resistance of the paint film. It is also possible to not completely immerse the test panel in water, but only immerse 2/3 or 3/4, and do not observe immediately, but observe when the paint film returns to its original state after a certain period of time. For many paint materials, due to the adsorption of water and the interaction between water and the hydrophilic components in the film-forming material, the whitening of the paint film can disappear completely after drying in the air. The time at which this blanching disappears must be recorded. This test is preferably carried out in parallel on not less than two to three plates.

Determination of water resistance of paint film by OCT standard method (OCT10086-39 test method 31)

The determination of the water resistance of the paint film (quantitative determination) is carried out on two white iron plates measuring 50x100 mm. Paint the iron plate, and when the paint film is flat and dry according to the technical conditions, hang 2/3 of the iron plate vertically in a glass bath filled with distilled water (temperature 20°C): take the test plate out of the water, remove the After the water polo well is dried in the air for 2 hours, observe the state of the paint film (after the test); the beginning of loss of light, whitening and damage to the paint film (formation of rough particles, bubbles, wrinkles, peeling, etc.) Recorded in the field. (Related instruments: constant temperature Water Tank)

Determination of swelling properties of coating films on wood surfaces

For the determination of the expansion of the paint film on wooden boards, air-dried pine boards measuring 70x150x10 mm are used; the edges and corners of the pine boards must be rounded. Each side of the test panel is coated with two to three layers of the sample; after the last layer is dried, weigh it for 120 hours and place it in water (18~20°C). The perimeter of the pine boards should be pre-coated with Mendeleyev putty or a mixture of wax and rosin. After a certain period of time, take out the test plate from the water, wipe it dry with filter paper and weigh it.

Determination of water swelling of stripped paint films

The paint film was prepared by shallowing "Filigerlan" brand cigarette paper (dimensions 100-x50 mm) in the test samples. The first layer is soaked from one direction and the second from the opposite direction; this results in a film of uniform thickness. After drying, use scissors to cut from the four sides so that the size of the paint film left after cutting is 75x40 mm. In this way, five to six paint films were prepared.

Put the paint film on the small glass iron and hang it on the glass column. Transfer the paint film together with the glass column into a desiccator containing calcium fume before the first weighing. After half an hour, weigh the original piece of paint film together with the glass hook in turn, and then place it in a desiccator that maintains the necessary humidity. After a certain period of time (every day and night), take out the paint film from the constant Humidity Chamber (dryer) . Quickly weigh it with a paper swab. The paint film and the glass hook are sent in and taken out with pliers.

A graph of the swelling degree of the paint film for several paint materials.