彩涂卷的耐干热试验

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彩涂卷经规定温度和规定时间烘烤老化后，评定其涂层失光、变色、起泡、开裂、T弯性能的变化和涂层抗脱落性能的变化等。或预先进行T弯处理的彩涂卷经烘烤老化后，评定其T弯处的涂层抗脱落性能和开裂变化的过程叫耐干热试验。

彩涂卷的耐干热试验对不同的试验方式有不同的技术要求

(1)平板试样的加热试验。试验前先测定试样的光泽和色度坐标值。然后将试样放人烘烤炉中加热到规定时间，取出并放16h后，按GB/T17661995标准评定其失光和变色等级，取平行试样的最差值为试验结果。

(2)经T弯处理后试样的加热试验。将试样制备成规定T弯值的试验样。像平板试样一样，将试样放人烘烤炉中，试验后取出也按GB/T1766-1995标准评定试样T弯处的失光和变色等级，取平行试样的最差值为试验结果。

(3)试样经加热老化后的T弯试验。准备不少于3件试样，留下一件作试验后的对照样用。其余的与平板试样一样放炉中试验，试验后取出与对照样一起作T弯试验，然后评定经加热老化的试样T弯值的变化，取平行试样的最差值为试验结果。

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.