The key to create a stable emulsion is to obtain finest droplet. The more shear energy is introduced into the mixture, the smaller size of droplet will be. As for high shear emulsifying machine, the function of shearing directly decides emulsification result.
Then you must wonder what factors are related with shearing effect, and how to improve it. Generally speaking, we know that the sharpness and hardness of the blade edge, the gap between stator and rotor, the size of passable droplet, and the motion velocity of rotor are all elements influencing emulsification result. If first three are settled or disinclined to make a change, the motion velocity thus becomes the principal determinant.
The motion velocity we mentioned is referred to peripheral linear velocity of rotor(stator is fixed). The faster it runs, the more possibility of shearing, impacting, avulsing and dispersing energy obtained by radial liquid or paste flow will be, and the finer droplet we get. However, the motion velocity could not be too much high. When it speeds up to a max level beyond regulated capacity, “barrier shield” is formed for super-speed rotation that largely obstructs the flow of mixture, leading to the consequence that little material are emulsified but much heat are generated. Even worse, some materials would aggregate instead.
Then what we often called stirring rate is shear velocity? The answer is NO. Velocity has two different definitions: angular velocity and linear velocity. And the shear velocity refers to the latter one. There’s a conversion formula: linear velocity=angular velocity×radius(v=r). This is why stirring rate of industrial emulsifying machine is 3000rpm or 1500rpm, but lab-use emulsifying mixer is 10000rpm or even higher to 280000rpm. The radius plays a huge role to equal their linear velocity so as to get similar emulsification effect. From another point of view, small batch production is one of the features of lab experiment, then the diameter of homogenizer head must be corresponding reduced. To avoid negative effect caused by small radius, we have to enhance the angular velocity. Hence, high speed lab homogenizer comes into being.
Applications of homogeneous emulsifying mixer
- Cosmetics & Toiletries: cream, lotion, wax, mascara, gel, toothpaste, etc.
- Pharmaceuticals: ointment, dental composite, syrup, injection,etc.
- Food: mayonnaise, dressing, jam, butter, margarine, wasabi, etc.
- Chemicals: polyester, synthetic fiber, shoe cream, etc.