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.
Bend 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 test
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.
