| Abstract: |
The interphase between a polymer film and a substrate controls the adhesion and durability of a variety of polymeric systems including adhesives, coatings on plastics and metals, and electronic packaging. A polymeric coating system consists of a coating film applied to a substrate. Interphase formation is affected by processing conditions that control chemical kinetics, diffusion, volumetric changes, and internal stress. In addition, the interphase often includes impurities, unreacted molecules, or additives. The resulting interphase can be a very complex structure, which is not easily analyzed. In this study, phase imaging atomic force microscopy (AFM) is used to examine the interphase of a number of coating/substrate systems. Parameters investigated include resin molecular mass, stoichiometry, substrate type, and curing conditions. Specimens are prepared by applying thin (<500 nm) and thick (>1 {M}m) films of coatings on the substrates. Crossed sections and interior surfaces (surfaces in contact with the substrates) are used for interphase characterization. Both phase and topographic imaging AFM are performed using tapping mode AFM under ambient conditions. Interpretation of AFM results is aided by data collected using nanoindentation. AFM results reveal that curing conditions, stoichiometry, and resin molecular mass have a strong influence of the thickness of the interphase and that microstructure of the film surface in contact with the substrate is different from that of the film surface in contact with the air. The effects of TPO bulk and surface microstructures on paint/TPO adhesion are discussed. |
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