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LUDOX® AS-40 is an alkaline dispersion of amorphous silica typically used as a binder in high-temperature applications. Request a sample online today.
LUDOX® AS-40 is an ammonium-stabilized dispersion of negatively charged, amorphous colloidal silica particles with an average particle size of approximately 22 nanometers. LUDOX® AS-40 particles have a high surface area, rich in silanol groups. This makes LUDOX® AS-40 an excellent binder for metals, oxides, siliceous materials, and polymers with reactive functional groups.
Standard colloidal silica grades such as LUDOX® HS-40 and TM-40 are stabilized with sodium ions that can act as a flux at high temperatures. Since LUDOX® AS-40 is stabilized with ammonium ions rather than sodium, it is better suited for use in applications such as vacuum-formed fibrous shapes and refractory manufacturing. LUDOX® AS-40 is also ideal in catalyst applications where the presence of sodium stabilizing ions is detrimental, such as zeolites and emission-control products. When included in water-based coating formulations, LUDOX® AS-40 becomes an integral component of the polymer matrix and increases the durability, antiblocking, and antisoiling properties.
CAS number: 7631-86-9
Silica content, wt%: 39–41
Specific surface area, m2/g: 135
Average particle size, nm: 20–24
pH: 9.1
Density, g/cm³: 1.29
Specific gravity (@ 25°C): 1.30
Viscosity (@ 25°C), cP: 11
Particle charge: Negative
Stabilizing counterion: Ammonium
Primary Chemistry: Colloidal Silica
Instability of binders in extremely high-temperature applications Failure of binding material caused by sodium Poor cohesive strength of ceramic or refractory materials Inadequate adhesion of water-based coatings or adhesives to inorganic substrates Insufficient resistance of water-based coatings to soiling or abrasion
Refractories Inorganic catalysts Water-based coatings Water-based adhesives
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