Coatings 2023 , 13 , 195
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Figure1. Representative normalization curve (H39K 80 over KP substrate—Cobb test). 3. Results 3.1. Sample Preparation The coated samples achieved an average dry coat thickness of 7.2 ± 2.5 μ m (represen- tative SEM micrographs are reported in Appendix B). The high standard deviation is due to the presence of kaolin in the experimental formulations. Whereas kaolin ratio and dry coat density are directly proportional, coat thickness is inversely proportional to kaolin content. Indeed, at a given dry solid content in the experimental formulations, a higher kaolin content means a lower dry volume deposited, hence a reduced coat thickness. All formulations were successfully applied to the substrates. However, some issues were encountered while applying H39K 100 and H40K 100 to KP. As represented in Figure 2, the observed issues were related to visible defects.
( a )
( b ) Figure 2. ( a ) H39K 100 coating over KP substrate after drying: grooves affect the aesthetical and perceptive properties of the coated sample; ( b ) SEM micrograph (magnification: 250 × ) showing the grooves at a larger scale. ImageJ processing shows peak distance of around 150 μ m. Specifically, stripes were attributed to the wire wound on the K-Bar, as confirmed by SEM micrographs. Indeed, Figure 2b was analyzed with ImageJ in 15 different points, measuring the average peak distance of the grooves. The results report a 150 ± 6 μ m average distance, which corresponds to the diameter of the wire wound on the K-Bar. Such
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