LUDOX® AS-40 is an alkaline 40% aqueous dispersion of colloidal silica with a particle size of 22 nm. It is stabilized with ammonium and used as a high temp binder and catalyst in a wide range of industrial applications.
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Product Overview
LUDOX® AS-40 is an ammonium stabilized dispersion of negatively charged, amorphous colloidal silica particles. LUDOX® AS-40 particles have a high surface area and the surface of these particles is rich with silanol groups. This makes LUDOX® AS-40 an excellent binder of metals, oxides, siliceous materials, and polymers with reactive functional groups. Standard colloidal silica grades are stabilized with sodium ions that can act as a flux at high temperatures. Because LUDOX® AS-40 is stabilized with ammonium ions rather than sodium, it is better suited for use in high temperature applications.
Product Specifications
Colloidal Silica
Silica Content: 39-41%
Specific Surface Area: 135 m2/g
pH: 9.1
Specific Gravity: 1.30 (@25°C)
Viscosity: 11 cP (@25°C)
Particle Charge: Negative
Stabilizing Counter Ion: Ammonium

Primary Chemistry: Colloidal Silica
Features & Benefits
Anionic Particles
Excellent surface modification
Outstanding formulation stability
Suitable for high temperature applications
High binder performance
Small particle size
Ammonium stabilized
Stabilized against gelation
Non-porous and uniformed
Problems Solved
Instability of binders in extremely high temperature applications.
Failure of binding material caused by sodium.
Poor cohesive strength of ceramic and refractory materials.

LUDOX® AS-40 is an excellent binder for high-temperature applications such as vacuum formed fibrous shapes and refractory manufacturing. LUDOX® AS-40 is also used in catalyst applications such as zeolites and emission control products where the presence of sodium stabilizing ions is detrimental. When included in water-based coating, adhesive, or sealant formulations LUDOX® AS-40 becomes an integral component of the polymer matrix and increases the durability of the latex film. Incorporation of LUDOX® AS-40 into latex paints also improves the anti-blocking and anti-soiling properties of the coating.