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See Chinese contents: GB/T 6742-2007 GB/T 6742-2007: Paints and varnishes -- Bend test (cylindrical mandrel)
This standard specifies an empirical test method, for evaluating the resistance of coatings of paints, varnishes or related products to cracking and/or peeling from metal or plastic substrates, when bent about a cylindrical mandrel under standard conditions. For multi-coat systems, each coating can be tested separately or the entire system can be tested. The test can be carried out in the following two ways: - As a and quot;pass/fail and quot; test, i.e., using a mandrel of specified diameter to assess whether the coating complies with specified requirements; - Test the mandrels in sequence, to determine the maximum mandrel diameter at which the coating will crack and/or peel off the substrate. This standard specifies two types of instruments, Type I and Type II. Type I is suitable for test panels which have a thickness not greater than 0.3 mm; type II is suitable for test panels which have a thickness not greater than 1.0 mm. Both instruments give similar results for the same coating; however, when testing a given product, it is common to use only one instrument.
