Colloidal Silicon Dioxide|Fumed Silica

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: 

Classification of Excipients.

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.

Cleanroom classification.

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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