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We have used our modified SPM, equipped with a custom-made probe, consisting of a diamond tip and rectangular tungsten cantilever, to measure the mar resistance of a number of cross-linked polymeric surface coatings, at micron and submicron scales. With the unique high resolution of SPM, the dimension of the mars can be measured with great accuracy, thus different responses of coatings to the marring stress, i.e., elastic recovery, plastic deformation, and abrasive wear, can be identified quantitatively. In addition, the dynamic process of marring, including viscoelastic creep, strain-hardening, micro-cracking, and surface fatigue, has also been studied with the SPM.
Fig. 1. Force Calibration and MIH Measurement
Fig. 2. A schematic illustration of how to calculate the MMR and different responses of the coating to marring stress.
Fig. 3. The resulting mars of two different hard-coatings under the same series of normal forces.