After baking and aging at specified temperature and time, the changes of gloss loss, discoloration, blistering, cracking, t-bending performance and anti peeling performance of the coating were evaluated. The process of evaluating the anti peeling performance
and cracking change of the coating at the T-bend is called dry heat resistance test. The dry heat resistance test has different technical requirements for different test methods
(1) Heating test of plate sample. Before the test, the coordinate values of luster and chromaticity of the sample were measured. Then put the sample into the baking oven and heat it to the specified time, take it out and put it for 16h, and evaluate the light loss and color change grade according to CB / t1766-1995 standard, and take the maximum difference of parallel sample as the test result.
(2) Heating test of samples after T-bend treatment. The samples are prepared into test samples with specified T-bend value. Like the flat sample, the sample is put into the baking oven and taken out after the test. The grade of loss of light and discoloration at the T-bend of the sample is also evaluated according to the GB / t1766-1995 standard, and the worst value of the parallel sample is taken as the test result.
(3) T-bend test of samples after heating aging. Prepare no less than 3 samples, and leave one for the control sample after the test. The rest of the samples are put into the furnace for test just like the flat sample. After the test, they are taken out and tested together with the control sample for T-bend test. Then the change of T-bend value of the sample after heating aging is evaluated, and the maximum difference of the parallel sample is taken as the test result.