Coatings 2023 , 13 , 195
8of 16
Figure 6. WVTR values for the uncoated (UC), commercial (SA-B and SB-B), and experimental dispersion coatings. 3.4. Grease Permeability Grease permeability was successfully improved compared with UC samples, where KB has a resistance of a few seconds and KP of up to 7 min. The results are reported in Figure 7. It is possible to observe differences as high as two orders of magnitude, depending on whether the KB or KP substrate is considered.
Figure 7. Grease permeability values for the uncoated (UC), commercial (SA-B and SB-B), and experimental dispersion coatings. An asterisk (*) represents the samples that reached the end of the test. According to the considered standard [30], the test ends after 24 h. In this work, it was observed how several sample conditions resisted the ultimate test time, especially if coated on KP. Therefore, actual resistance is higher than 1 day. Such conditions are highlighted with an asterisk in Figure 7. In general, kaolin-filled experimental dispersion coatings showed higher grease barrier performance compared with H39K 100 and H40K 100. Moreover, kaolin-filled H39K formulations reached similar values on KB and KP substrates. Such behavior confirms, as for the WVTR performance, the beneficial presence of kaolin in the formulation. Despite some high standard deviations (even a small defect that allows grease permeation forces the test end), it generally seems how the best-performing experimental formulation contains around 20% of kaolin (dry mass weight). 3.5. Spectrophotometry CIE L*a*b* coordinates for KB and KP substrates are reported in Figure 8. As clearly visible, the addition of kaolin slightly decreases a* coordinate and increases b* one, moving towards green-yellow hues. Lightness, generally, is reduced for every coated sample compared with UC samples.
Made with FlippingBook - professional solution for displaying marketing and sales documents online