The skinning tendency of oxidatively drying clearcoats and paints in storage is a long-standing problem. It is also an item of storage stability test content, but sometimes it is listed separately for special test. Skinning of paint products will not only change the proportion of paint components and affect the film-forming performance, but also cause various other ills of the paint, resulting in a decline in construction quality. Therefore, it is necessary to avoid and prevent it. The nature of the skin. At present, adding anti-skinning agents to coatings, or making the product have a certain thixotropy, are some measures taken to reduce and prevent skinning.
There are two main aspects in the measurement of skinning: one is to measure the possibility , and the other is to measure the speed of skin formation during use after opening the barrel. For some coatings, in the case of an open bucket, the skinning phenomenon cannot be completely avoided, but how to control the speed and properties of the skinning formation within the allowable range to minimize losses, then It is a problem that paint producers should pay attention to.
(1) For the airtight test, it is recommended to use a glass bottle with a screw top cover, fill it with 2/3 of the sample volume, screw the top cover tightly, put it upside down in a dark place, and check it regularly or until the crust is formed.
(2) Fill the test sample in the open tank to half the depth of the paint tank, open the cover and observe it from time to time until the skin forms. In the above two tests, it is better to use a sample with known crust properties to store at the same time for comparison, so as to compare the crust conditions of the two at different stages.
The Japanese JIS specification K 5400 lists the skinning test method for reference.
