Nano-Indentation of Thin Plasma Polymer Coatings on Compliant PET Substrates
(Room Exhibit Hall A)
30 Apr 19
2:30 PM
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4:00 PM
Quantitative mechanical characterization of thin stiff films deposited on compliant PET substrates still poses a major challenge. A minimal indentation depth is required as the surface roughness could influence the actual contact area between the indenter and the coating. Increasing the indentation depth often leads to underestimations of the mechanical properties as the substrates elastic response influences the measurement. The lack of a range were the mechanical properties can be measured with standard techniques us to look for alternatives. A possible approach for the mechanical characterization of thin coatings is offered by an Atomic Force Microscope (AFM) as highly sensitive nano-indenter with mapping capabilities that allow for a better understanding of the measurement limitation and show that it is indeed possible to characterize these coatings without considering the substrate influence. This paper compares classical indentation measurements with PeakForce QNM measurements (Bruker) and Atomic Force Acoustic Microscopy measurements. The effect of the surface topography on the mechanical characterization is discussed. However, the lack of a proper calibration sample limits the quantitative characterization possibilities. We propose a novel tip calibration approach to extract quantitative data from stiffness measurements provided by the AFAM method. The results obtained will be compared to QNM results.