Study on thickening of water-based inorganic zinc-rich coatings (3)

2.2 The thickening effect of polyurethane thickeners on water-based inorganic zinc-rich coatings
The addition of silicone propylene emulsion to prepare an organic-inorganic composite substrate can increase the compatible between polyurethane thickeners and substrates. The addition of silicone propylene emulsion has greatly improved the mechanical properties of water-based inorganic zinc-rich coating coatings, and the anti-corrosion properties have been guaranteed.
the ACRYSOL RM-8W, ACRYSOL SCT-275, RHEOLATE 299, NOPCO SN-612 these four polyurethane thickeners with ddipropanol methyl ether after thinning in accordance with the experimental method of 1.2 prepared 50 g water-based inorganic zinc-rich coating base parts, of which the organic emulsion compound ratio of 40%. The effect of thickener addition on the viscosity of the base material was tested, and the results are shown in Figure 3.The amount of polyurethane thickeners added is 8 g, the viscosity of the substrate increases from 9.2 mPa to more than 77 mPa and s before addition, which is much more obvious than the thickening effect of inorganic gel LT; Compared with inormeric gel thickener LT, the 4 polyurethane thickeners tested have a much better thickening effect and anti-sinking effect, mainly because polyurethane-type thickeners have a wider range of applicable pH values, their own performance is very small affected by pH. In addition, according to the parameters listed in Table 3, the active ingredient content of SN-612 in the selected thickeners is higher than that of the other 3 models, so the thickening effect is greater.The thickening of polyurethane-like thickeners is achieved by the connection between molecules and adsorption on the surface of latex particles, mainly in the composite system with unit subs or chain segments, thickening effect is related to the composition of latex particles, particle size, emulsifying agent type. Therefore, the higher the compound ratio of organic-inorganic, the greater the compatible, stability and effect of polyurethane thickeners in the system. When organic emulsions account for more than 30% of the base material, thickeners can show better compatibility and stability in the system. The use of polyurethane thickeners not only meets the basic requirements of the viscosity required for spraying, but also gives the coating surface a higher fullness, and has less effect on the coating film in terms of water and salt spray resistance..