LUDOX® SM-AS is an ammonium stabilized colloidal silica with 7 nm particle size. It is used as a binder in applications that require extreme temperatures.
Product Overview
LUDOX® SM-AS is an alkaline, aqueous dispersion of synthetic amorphous silica with a particle size of 7 nanometers. The silica particles carry a negative charge and work well to bind metals and oxides. LUDOX® SM-AS is stabilized with ammonium instead of sodium and therefore is more stable at ultra high temperatures than sodium stabilized colloidal silica.
Product Specifications
Density (g/cm³, lb/gal): 1.16, 9.7
Boiling Point (760 mm Hg) °C/°F: 100/212
Melting Point °C/°F: 0/32
Vapor Pressure (25°C) mm Hg: 24
Vapor Pressure (38°C) mm Hg: 48
Stabilizing Counter Ion: Ammonium
Particle Charge: Negative
Primary Chemistry: Colloidal Silica
Features & Benefits
Anionic particles
Very small particle size / high surface area
Narrow particle size distribution
Strong bond strength and stability in most applications
Low sodium levels
Fugitive counter ion
Problems Solved
Incompatibility of a water based formulation with sodium ions.
Failure of refractory binders at very high temperatures.
Poor adhesion of structural adhesives and sealants to metal surfaces.
Contamination of waste water with cationic particles.

LUDOX® SM-AS is an ideal binder for ceramics applications requiring extreme heat resistance. It is especially useful in binding refractory fibers for firebrick and other refractory applications.

LUDOX® SM-AS can be used in latex coatings and adhesives to improve durability, heat resistance, and adhesion to metal and glass surfaces.

The electrostatic nature of LUDOX® SM-AS makes it an efficient flocculant for waste water treatment and papermaking applications where positively charged contaminants like proteins must be coagulated and removed.

In concrete densifiers, LUDOX® SM-AS provides the silica necessary to interact with remaining calcium hydroxide in cement to create new calcium silica hydrate and increase concrete density.