After baking and ageing at specified temperature and time, the changes of gloss loss, discoloration, foaming, cracking, T-bending properties and anti-shedding properties of the coatings were evaluated. Or the process of evaluating the anti-shedding property
and cracking change of T-bend coatings of color coated panels after baking and aging is called dry-heat test.
Dry heat test has different technical requirements for different test methods.
(1) Heating test of plate specimen. The gloss and chroma coordinates of the sample were measured before the test. The samples were then heated in a baking oven for a specified time. After 16 hours of extraction and release, the loss of light
and color of the samples were evaluated according to GB/T 1766995 standard, and the maximum difference of the parallel samples was taken as the test result.
(2) Heating test of specimen after T-bending treatment. Samples were prepared into test samples with specified T-bending values. Like the flat sample, the sample is put into the oven. After the test, the grade of loss of light and color at
the T bend of the sample is evaluated according to GB/T 1766-1995 standard, and the maximum difference of the parallel sample is taken as the test result.
(3) T-bending test of the sample after heating and aging. Prepare not less than three samples and leave one sample as a control sample after the test. The other samples were put into the oven as the plate samples. After the test, the T-bending
test was carried out with the control samples. Then the change of T-bending value of the heat-aged samples was evaluated, and the maximum difference of the parallel samples was taken as the test results.