Understanding the Role of Fumed Silica in Adhesives

Formulators use particles to enhance the functionality of existing polymer matrices for adhesive and sealant products. Fumed silica is commonly used as a rheology control additive to provide sag resistance, anti-settling of fillers, and shear-thinning viscosity. The generic term “fumed silica” defines a range of products with different surface chemistries—from hydrophilic to hydrophobic. These products have differing compatibility with polymer systems, which enable formulators to fine-tune rheology performance. At the same time, formulators can enhance the viscoelastic response of films or the material properties of cured systems by controlling particle-particle interactions and particle–matrix interfacial adhesion. Such interactions can provide a means of securely incorporating hard materials, which lengthen fracture paths, and dissipate energy at interfacial junctions.1 These properties strengthen films and solids. In addition to the well-documented benefits of rheology control, fumed silica enhances the strength of cured adhesives. Following are three examples where fumed silica reinforces a polymer, resulting in a higher-performing adhesive or sealant. Transparent Silyl-Terminated Polymer: Customers in the do-it-yourself (DIY) market prefer high-clarity transparent silyl-terminated polymer (STP) adhesives and sealants. In Europe, manufacturers of these products have switched to clear packaging to highlight this benefit. Additives such as waxes, clays, and calcium carbonates are commonly used for rheology control and reinforcement of STP adhesives and sealants. The selection of these reinforcing aids typically results in an opaque product because the refractive index of these products does not match the matrix. By contrast, the index of refraction of fumed silica closely matches the transparent polymers commonly used in these products. Fumed silica is widely used to reinforce transparent STP adhesives and sealants. If you are looking for high quality, high purity and cost-effective Fumed Silica, or if you require the latest price of Fumed Silica, please feel free to email contact mis-asia.