Impact of Different Thickeners on Anti-Sagging Performance of Waterborne Industrial Paints
Why Anti-Sagging Performance Matters in Waterborne Industrial Paints
Sagging remains one of the most common application defects in waterborne industrial coatings. When applied to vertical surfaces or complex geometries, the coating can flow under gravity, resulting in material loss, non-uniform film thickness, surface defects, and reduced protective performance. Achieving a balance between anti-sagging performance, leveling, and application viscosity is therefore a primary objective in waterborne coating formulation.
Among the available rheology modifiers, fumed silica, polyamide wax, and polyurethane thickeners are widely used. Their thickening mechanisms differ significantly, leading to measurable differences in anti-sagging performance.
Experimental Evaluation of Different Thickener Systems
Test Method
To compare the anti-sagging performance of different rheology modifiers, HIFULL technicians evaluated formulations containing fumed silica, polyamide wax, and polyurethane thickener using the step blade method. The anti-sagging limit of each formulation was determined under identical testing conditions.
Figure 1
Figure 1 compares the anti-sagging performance of each thickener at addition levels of 0.5% and 1% against the blank formulation.
The blank sample achieved a maximum non-sagging film thickness of only 75 μm.
Adding 0.5% HL-200 fumed silica increased the anti-sagging thickness to 175 μm. Raising the dosage to 1% further increased the value to 275 μm, representing the highest anti-sagging performance among all tested formulations.
Polyamide wax reached 175 μm at a 0.5% addition level and 225 μm at 1%.
The polyurethane thickener achieved 175 μm at 0.5% and 200 μm at 1%.
Under the same formulation and test conditions, HL-200 fumed silica delivered the highest anti-sagging limit, while both organic thickeners showed lower resistance to sagging as film thickness increased.
HL-200 fumed silica Characteristics
| Properties | Unit | Typical Value | Testing Standard |
|---|---|---|---|
| Specific surface area(BET) | m2/g | 200±20 | GB/T 20020 |
| pH in 4% dispersion | 3.9～4.5 | GB/T 20020 | |
| Loss on drying(2 hour at 105℃) | % | ≤2.0 | GB/T 20020 |
| Loss on ignition(2 hour at 1000° based on material dried for 2 hours at 105℃) | % | ≤2.0 | GB/T 20020 |
| Sieve residue(45μm) | mg/kg | ≤250 | GB/T 20020 |
| Silica content( Based on ignited material) | % | ≥99.8 | GB/T 20020 |
| Tamped density（Based on material dried for 2 hours at 105℃） | g/L | 40～60 | GB/T 20020 |
HIFULL® HL-200 (BET=200㎡/g)
Why Fumed Silica Provides Better Anti-Sagging Performance
Three-Dimensional Hydrogen-Bond Network
The performance of hydrophilic HL-200 fumed silica is closely related to its microstructure. The material has a specific surface area of up to 200 m²/g and contains a high concentration of surface silanol groups.
Inside the coating matrix, these silanol groups form a three-dimensional hydrogen-bonded network. At rest, the network produces high low-shear viscosity, allowing the wet coating to resist gravity and maintain film build on vertical substrates.
Application shear temporarily breaks the network, reducing viscosity and improving leveling. Once the shear force is removed, hydrogen bonds rapidly reform and the viscosity recovers within a short period. This rapid and reversible structural recovery provides strong thixotropy, which explains the superior anti-sagging performance of fumed silica compared with polyamide wax and polyurethane thickeners.
Comparison of Thickener Performance
Fumed Silica vs. Polyamide Wax vs. Polyurethane Thickener
The experimental results indicate that all three thickener systems improve anti-sagging performance compared with the blank formulation. The degree of improvement, however, differs substantially.
Fumed silica exhibits the highest anti-sagging limit because its inorganic particle network rapidly rebuilds after shear, maintaining high structural strength during film formation. Polyamide wax improves sag resistance through its crystalline network but provides a lower maximum film build under identical dosage conditions. Polyurethane thickeners primarily increase viscosity through associative interactions within the aqueous phase, resulting in comparatively lower anti-sagging performance in this evaluation.
For waterborne industrial coatings requiring high film build on vertical surfaces, fumed silica provides a more effective rheology control mechanism.
Further Reading:
HIFULL Fumed Silica for Waterborne Industrial Coatings
Hubei Huifu Nanomaterial Co., Ltd. specializes in the research, development, and production of fumed silica and other nanomaterials for industrial applications. Advanced manufacturing technology and stringent quality control ensure consistent product quality from batch to batch.
HIFULL® fumed silica combines proprietary surface-modification technology with precise particle-size control to deliver excellent thickening efficiency and thixotropic recovery in waterborne industrial paint systems. These properties help coating manufacturers improve application stability, reduce coating defects, and maintain consistent film quality across industrial production.
Paints & Coatings
Applications of High Anti-Sagging Waterborne Coatings
Improved anti-sagging performance is increasingly important as waterborne industrial coatings are adopted for steel structures, pipelines, engineering machinery, storage tanks, manufacturing equipment, and automated production lines. Selecting an appropriate rheology modifier remains one of the most effective approaches to achieving stable application performance, consistent film thickness, and improved coating quality in these industrial environments.
ABOUT HIFULL
Our main products are fumed silica SiO2, fumed titanium dioxide TiO2, and fumed alumina Al2O3. We get 20+ years of expertise and 20,000 tons of annual capacity. We supply total of 23 grades of hydrophilic & hydrophobic fumed silica. We get registration of REACH and pre-registration of K-REACH & KKDIK. We are the leading setting body of ISO18473-1:2015, ISO18473-3:2018, and ISO 23157:2021. Learn More About Hifull
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