METHODS FOR STUDY OF MECHANICAL AND TRIBOLOGICAL PROPERTIES OF HARD AND SOFT COATINGS WITH A NANO-INDENTER

摘要

This study illustrates the capabilities of a nanoindentation/nanoscratch tester to assess mechanical and tribological properties of coating films. Properties such as hardness, elastic modulus, mar and scratch resistance, and critical force for cracking can be accurately measured. Operation of the Nano-indenter is described in detail. A scanning probe microscope (SPM) is shown to be a valuable supplement to the Nano-indenter. Well-characterized thermoset acrylic clear coats and thermoplastic latex films were studied. For the first time, operating parameters are described for measurement of relatively soft coatings, such as films cast from a latex with a glass transition temperature (Tg) of 8 °C. Thus, the method is made available for study of most types of coatings. The method can easily discriminate between coatings with different Tg's and cross-link densities. Once operating parameters are established, it takes about 10 minutes for an indentation test and 10 minutes for a scratch test with the Nano-indenter, and with further automation this time could be reduced. Each indentation test accurately measures hardness and elastic modulus as a function of depth within the coating, and each scratch test provides additional insight into the material's behavior. The method is sensitive to small changes in polymer composition and formulation, and results are highly reproducible. The method's speed, sensitivity, and reproducibility make it a valuable tool for measuring basic coating properties, for carrying out optimization studies, and for developing standard tests, i.e. for mar and scratch resistance.