Flexibility / elongation is the pliability or rigidity of a material. It expresses the extent to which it resists bending. There are several empirical test procedures for assessing the resistance of a coating of paint, varnish or related product to cracking and/or detachment from a metal or plastic substrate. There are the bend test, the impact test and the cupping test.
Mandrel testers are common test apparatuses used for the determination of the elongation/and adhesion of coatings at bending stress. At a bend test a test panel is bend over a certain radius.
Conical mandrel testers bend the test panels over a conus so that a large variety of bending radii is tested at the same time.
The cylindrical mandrel test can be carried out as a quick pass/fail test with a single mandrel of specified diameter or as repeated procedure with decreasing mandrel diameters for determining the diameter of the first mandrel causing failure.
Impact tests are a test method for evaluating the resistance of a dry film of paint, varnish or related product to cracking or peeling from a substrate when it is subjected to a deformation caused by a falling weight dropped under standard conditions.