Colloidal silica, due to its unique properties such as high specific surface area, uniform particle size distribution, and surface modifiability, has wide applications in various industries. The acidic, basic, or neutral state of silica significantly impacts its properties and applications.
Acidic Colloidal Silica
- Properties:
- More active and reactive surface compared to neutral silica
- Ability to form stronger bonds with polar surfaces
- Applications:
- Concrete industry: As a water-proofing agent, increasing compressive strength and durability of concrete, improving adhesion of concrete to rebar, and accelerating concrete curing.
- Ceramic industry: As a binder, improving the mechanical and thermal properties of ceramics, reducing firing temperature.
- Paper industry: As a reinforcing agent, improving the water and oil resistance of paper, increasing the smoothness of the paper surface.
- Mechanism of Action:
- Reaction with surface hydroxides of concrete or ceramic particles and formation of strong siloxane bonds
- Creation of a three-dimensional network that increases strength and adhesion
Basic Colloidal Silica
- Properties:
- More active surface compared to neutral silica
- Ability to adsorb metal ions
- Ability to form stable gels
- Applications:
- Water treatment industry: As a coagulant, helping to remove suspended and colloidal particles from water
- Coating industry: As a matting agent, increasing the abrasion resistance and adhesion of coatings
- Textile industry: As a softener, improving the feel and appearance of fabrics
- Mechanism of Action:
- Adsorption of metal ions and formation of larger flocs that easily settle
- Creation of a protective layer on the fiber surface that causes softness and smoothness of the fabric
Neutral Colloidal Silica
- Properties:
- Low reactivity surface
- High chemical stability
- Applications:
- Polymer industry: As a reinforcement, improving the mechanical and thermal properties of polymers, reducing specific gravity
- Pharmaceutical industry: As a drug carrier, improving the flowability of drug powders
- Food industry: As an anti-caking agent, increasing volume and improving the texture of food products
- Mechanism of Action:
- Creation of a three-dimensional network that strengthens the polymer structure
- Increasing the contact surface between powder particles and improving flowability
Other Applications of Colloidal Silica
- Catalyst: Acts as a catalyst carrier or catalyst itself in chemical reactions.
- Thermal insulation: Due to its porous structure, it is used as a thermal insulator in various industries.
- Cosmetics: Used as a thickener and pigment dispersant in cosmetics.
In conclusion, the choice of colloidal silica type (acidic, basic, or neutral) depends on the desired properties and the final application. Each type of silica has its unique properties and applications, and by making the right choice, optimal results can be achieved.