Hydrophobic Fumed Silica in Polyurethane Zinc-Rich Coatings
Comparison of Thickening and Thixotropic Performance of Hydrophobic Fumed Silica in Polyurethane Zinc-Rich Coatings
Evaluating Thickening and Thixotropic Performance
In polyurethane zinc-rich coatings, controlling zinc powder sedimentation during storage and sagging during application is a key formulation challenge. The coating must maintain sufficient structure at rest while remaining easy to apply under shear. Fumed silica commonly adjusts viscosity and thixotropic behavior in these systems.
HIFULL® HB-151 and HB-152 are two hydrophobic fumed silica grades evaluated for these applications. To compare their performance with competing products, HIFULL technicians tested both grades alongside several competitor products and a blank sample in the same polyurethane zinc-rich coating system.
All samples were prepared at the same fumed silica addition level, allowing comparison of thickening and thixotropic performance under consistent conditions.
Test Conditions and Evaluation Parameters
The experiment was conducted using a polyurethane zinc-rich resin system with a fumed silica addition level of 1.8%. Viscosity was measured at low speed (6 rpm) and high speed (60 rpm), and the thixotropic index was calculated from the measured values.
Figure 1 presents the results for the different samples. The green bars represent the thixotropic index, the blue line indicates viscosity at 6 rpm, and the orange line indicates viscosity at 60 rpm. These measurements provide a basis for comparing the samples’ viscosity profiles under different test conditions.
Figure 1. Comparison of Thickening and Thixotropic Performance
Comparison of HB-151 and HB-152
The blank sample showed very low viscosity, indicating limited resistance to zinc powder sedimentation in the absence of fumed silica.
HB-151 delivered the strongest thickening performance among the tested samples at both 6 rpm and 60 rpm, outperforming several competing products under the conditions evaluated. It also showed the highest thixotropic index in the comparison. These results indicate that HB-151 provides effective viscosity control across the two measured conditions.
HB-152 also improved thickening and thixotropic performance compared with the blank sample, although its overall performance was slightly below that of HB-151.
The differences between the two grades provide a basis for further evaluating their suitability for polyurethane zinc-rich coating formulations.
Figure 2. Performance Comparison of HIFULL® HB-151 and HB-152
Factors Affecting Performance Differences
The specific surface area and carbon content of hydrophobic fumed silica can influence its dispersion behavior and interaction with the resin and filler components of a coating formulation. These properties are relevant when evaluating the performance differences between HB-151 and HB-152.
Polyurethane zinc-rich coatings contain high levels of zinc powder, making dispersion and rheological control important considerations during formulation. The surface characteristics of hydrophobic fumed silica can affect how particles interact within the resin system and how effectively they contribute to the formation of a three-dimensional network.
The observed differences between HB-151 and HB-152 can therefore be considered in the context of their respective material properties and behavior in the tested coating system. Further technical data and formulation-specific testing can help clarify the contribution of individual material parameters to the measured performance.
Paints & Coatings
HIFULL® Fumed Silica for Industrial Formulations
Hubei Huifu Nanomaterial Co., Ltd. specializes in the research, development, and production of fumed nanomaterials. Its hydrophilic and hydrophobic fumed silica products serve applications in coatings, adhesives, silicone rubber, food, and pharmaceutical formulations.
For manufacturers of polyurethane zinc-rich coatings, selecting an appropriate fumed silica grade requires consideration of the resin system, filler loading, storage stability, and application requirements. Comparing viscosity and thixotropic behavior under consistent test conditions provides a practical starting point for evaluating candidate grades and determining their suitability for a specific formulation.
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ABOUT HIFULL
Our main products are fumed silica, nano titanium dioxide, and nano aluminium oxide. We get 20+ years of expertise and 40,000 tons of annual capacity. We supply total of 23 grades of hydrophilic & hydrophobic fumed silica. We have registrations for EU-REACH, Turkey-REACH, K-REACH and UK-REACH. We are the leading setting body for ISO18473-3:2018, ISO23157:2021 and ISO18473-4:2022. Learn More About Hifull
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My name is Van, I’m the business manager of HIFULL, I have been in Fumed Silica Industry for more than 10 years. Feel free to contact me. I’m happy to provide you the best service and products.
