Colloid Mill – Pharmaceutical Engineering B. Pharm Third Semester PDF Notes



Colloidal mill works on the principle of rotor-stator

The size reduction is affected due to shearing, when the
material is passed between the narrow gap of milling surfaces of rotor and
stator. A rotor turns at high speeds of 3000 – 20000rpm.

The high levels of hydraulic shear applied to the process
liquid disrupt structures in the fluid. Colloid mills are frequently used to
increase the stability of suspensions, emulsions and can also be used to reduce
the particle size of solids in suspensions

Higher shear rates leads to smaller droplets of 1 micron.
Based on a rotor rotating at high speed and very close to a conical stator, the
particle size is done by modifying the gap between the rotor and the stator.


• A colloidal mill consist of a high speed rotor and a
stator with a conical milling surfaces between

• Which is an adjustable clearance ranging from 0.002 to
0.03 inches

• The rotor speed is 3000 to 20000 rpm. The material to be
ground should be pre milled as finely as possible to prevent damage to the
colloidal mill

• Rotors and the stator may be smooth surfaced or rough
surface. With the rotor and the stator there is a thin uniform film of material
between them and it is subjected to the maximum amount of shear


The material is placed into the mill though the inlet
hopper. It is then passed through the narrow gap between the rotor and stator
and thus reduced the fine particle size

A colloid mill is a hydraulic shear producing device

The colloid mill works to reduce the size of the suspended
droplets. The mill allows the solid particles to become so small

The process of colloid milling is done through the addition
of the heavier liquid into the chamber of the mill that performs the shearing
process. Once the heavier liquid has been added the lighter material whether it
is a solid mass or a liquid of different viscosity is added to the material to
start the mill. When the milling portion of the function takes place, the
materials are both stirred together within the mill at a high rate of speed

In other model the stator remains constant and the rotor
will do the function of rotation.

It creates the amount of hydraulic shear needed to break
down the materials


• High throughput with excellent grinding result

• Infinitely adjustable gap settings between rotor/stator
for control of particle size reduction

• Suitable for products of high viscosity range

• Capable of operation under pressures up to 16 bar

• High-value seal with wear-resistant materials

• High quality surface finishes for easy cleaning

• Other materials and finishes are available upon request

• Machine is self-draining

• Low noise levels


• Requires high power for the running of the colloidal mill

• Using of wet materials

• Consumes more energy


Colloid mill is used for preparing suspensions, emulsions
and ointments

Capable of producing pharmaceutical products with reduced
particle size   < 1 μ

Colloidal mill can be sterilized so it can be used in the
production of sterile products

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