THE SCRATCH TEST - DIFFERENT CRITICAL LOAD DETERMINATION TECHNIQUES

Different techniques for determining the critical load of coated products (microscopy, acoustic emission, and normal, tangential and lateral forces) are presented and the suitability of each is discussed. It appears that the most straightforward technique is microscopic observation. Among the methods based on the use of a physical measurement, acoustic emission detection is the most effective. The dynamics ratio between the signals below and above the critical load for the acoustic emission (much greater than 100) is well above that obtained with the normal, tangential and lateral forces (from less than 5 to 10). The fields of application of the scratch test as an adhesion test are discussed.