Fumed Silica vs Nano Alumina: Thixotropy in UV Coatings
Rheological Characteristics in UV Coating Systems
The application and storage stability of UV-curable coatings are governed by system viscosity and thixotropy. Fumed nanomaterials are widely utilized as rheological modifiers due to their small particle size and surface effects. However, fumed silica is far more prevalent than nano aluminium oxide in practical formulations. HIFULL evaluated the distinct viscosity and thixotropic responses of both materials at varying addition levels in UV coatings to clarify their underlying rheological mechanisms.
Rheological Response of Nano Aluminium Oxide
As shown in Figure 1, increasing the dosage of nano aluminium oxide produces a moderate, linear rise in overall coating viscosity with negligible impact on thixotropy.
This behavior stems from the low surface hydroxyl group density on nano alumina particles. Interparticle interactions rely primarily on weak van der Waals forces, building a loose spatial network that exhibits minimal structural breakdown between low-shear and high-shear conditions.
Rheological Response of Fumed Silica
As illustrated in Figure 2, increasing fumed silica loading yields a rapid rise in coating viscosity, accompanied by a linear increase in the thixotropic index.
Surface silanol groups on fumed silica particles aggregate via hydrogen bonding, constructing an interconnected three-dimensional network throughout the resin matrix. Under static conditions, this network restricts molecular mobility, elevating system viscosity.
Under high shear stress, the hydrogen-bonded network reversibly dissociates, causing an immediate drop in viscosity and restoring coating fluidity. Upon shear removal, the hydrogen-bonded network gradually reconstructs. This reversible shear-thinning response provides ideal thixotropic control.
Additive Selection & Formulation Guidelines
In UV formulation design, additive selection depends on the target performance requirements:
Nano Aluminium Oxide
Selected to increase the mechanical hardness of the film and abrasion resistance, with minimal influence on system thixotropy.
Fumed Silica
Selected to control sagging in thick-film applications, enable vertical surface stability, and prevent pigment settling during storage.
Targeted control over primary particle size, specific surface area, and surface functionalization enables precise customization across varied coating matrices.
Paints & Coatings
Industrial Material Optimization
The distinct rheological behaviors of nano alumina and fumed silica reflect fundamental differences in interparticle surface forces. Hubei Huifu Nanomaterial Co., Ltd. manufactures specialized hydrophilic and hydrophobic fumed silica grades, leveraging particle size engineering, chemical surface modification, and silane grafting to provide stable rheological solutions for high-performance coating formulations.
Further Reading:
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
Hello, Customers
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.
