Colloidal Silicon Dioxide is commonly known as fumed silica.It is a very common and interesting excipient because it has a very small particle size and large surface area.
Interesting in the sense that only 10 kg of Colloidal Silicon Dioxide can fill approximately the 40 kg of empty bag. It is because of the fact that it is very light weight having low bulk density.
Manufacturing of Colloidal Silicon Dioxide
Colloidal Silicon Dioxide is manufactured using hydrogen-oxygen flame by hydrolysis of Silicon Tetrachloride at 1800°C after that it is rapidly cooled.
Other Names
Colloidal Silicon Dioxide is also known as
- Fumed Silica
- Aerosil
- Colloidal silica
- Fumed silicon dioxide
- Pyrogenic silica
- Cab-o-Sil
- Silica Sol
Uses of Colloidal Silicon Dioxide
It is used as
- Glidant (0.1-1%)
- Humectant
- Disintegrant
- Stabilize Emulsions (1.0-5%)
- Thickening & Suspending Agent (2.0-10%)
- Anti-Caking Agent
- Viscosity Enhancer
Also Read:
As Glidant
Colloidal Silicon Dioxide is commonly used as a glidant.
Glidant are the excipients which enhance powder flow by reducing inter-particle friction.
Colloidal Silicon Dioxide enhances flow because of the following 3 mechanisms
- Layer Formation
- Act As Sponge
- Negative Charge
Layer Formation
Particles of Colloidal Silicon Dioxide form a layer around the powders or granules and act like a ball bearing to roll the particles or granules by reducing the friction so flow properties are improved and powder or granules do not stick to the walls of hopper or blender.
Act As Sponge
Colloidal Silicon Dioxide acts as a foam which absorbs the moisture and enhances the flow.
Moisture in the powders or granules results in flow reduction due to increased friction.
Negative Charge
Colloidal Silicon Dioxide may develop a negative electrostatic charge and repel the powder particles and reduce friction thus flow is improved.
As Humectant
Colloidal Silicon Dioxide acts as a humectant and absorbs moisture.
As Disintegrant
Colloidal Silicon Dioxide is used as a disintegrant and it results in water attraction through water channels.
As Emulsions Stabilizer
Colloidal Silicon Dioxide is used to stabilize the emulsions.
Thickening & Suspending Agent
Colloidal Silicon Dioxide acts as a thixotropic thickening and suspending agent for semisolid preparations and gels.
Thixotropy
Thixotropy is the property in which viscosity is decreased with stirring or shearing and when stirring or shearing is removed viscosity again starts to increase.
Viscosity Enhancer
Colloidal Silicon Dioxide is used as a viscosity enhancer in suppository formulations.
Also Read:
Line Clearance in pharmaceuticals.
Other Uses
- Colloidal Silicon Dioxide prevents segregation of particles.
- Colloidal Silicon Dioxide helps to rearrange the particles in the die before compaction and results in strong bounding of powders or granules to prevent capping.
- For the spray drying process, Colloidal Silicon Dioxide is used in formulations to prevent choking of spray nozzles.
- Colloidal Silicon Dioxide prevents the formation of lumps on storage of powder or granular products.
Solubility
Colloidal Silicon Dioxide is insoluble in water.
Grades of Colloidal Silicon Dioxide
Following are the some grades of Colloidal Silicon Dioxide
- Colloidal Silicon Dioxide 130
- Colloidal Silicon Dioxide 200
- Colloidal Silicon Dioxide 300
- Colloidal Silicon Dioxide 380
Handling Precautions
Wear a mask and gloves before handling Colloidal Silicon Dioxide because inhalation of Colloidal Silicon Dioxide may result in irritation of the respiratory tract.
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