Powder is a collection of many small particles. It has many discontinuous surfaces, with large specific surface area. The particle size is generally less than 1000μm. Powder has some physical properties, such as: fluidity, filling, cohesion and charge-ability. Powder fluidity is the basis of powder engineering, and it is an important indicator of powder performance.
For powder fluidity, there are several affecting factors. Next, let’s give a brief analysis about them.
Factors affecting powder fluidity
① Particle size and particle size distribution
Размер частицы: powder fluidity is closely related to particle size. Usually particle sizes between 10 and 100 microns can improve fluidity. Particle sizes that too large or too small will cause adverse influence on powder fluidity.
Particle size distribution: the uniformity of particle size distribution is crucial to powder fluidity. Evenly distributed powders have better fluidity, while uneven particle size distribution may lead to decreased fluidity.
② Particle shape
Even if with the same particle size, powders with different shapes have different fluidity. Spherical particles have the best fluidity because mutual contact area is the smallest. While flake or branch-like particles have more contact points, which means larger contact area and more shear force, so powder fluidity is poor.
③ Porosity
Porosity has a significant effect on powder fluidity. The higher the porosity, the lower the bulk density of the powder, and the better the fluidity; conversely, the lower the porosity, the higher the bulk density, and the worse the fluidity.
④ Temperature
As the temperature changes, powder fluidity will increase first and then decrease. Under low temperature conditions, the density of particles increases with the increase of temperature, this can helps to improve powder fluidity. However, when temperature is too high, the adhesion of powders will increase, resulting in low powder fluidity.
⑤ Moisture
When moisture content of the powder is low, moisture exists in the form of adsorbed water, so little effect on fluidity; When moisture content continues to increase, it will form a layer of water film between particles. The film increases the resistance to relative movement between particles, resulting in a decrease in powder fluidity; When moisture content exceeds the maximum molecular bound water, powder fluidity will deteriorate rapidly or even completely lose.
How to improve powder fluidity? Surface coating modification is one of the methods.
The principle of surface coating modification is to coat the surface of particles with a layer of modifier. The modifier usually has large specific surface area and multiprocessors structure, this can effectively disperse particles, reduce adhesion and aggregation between particles, and then improve powder fluidity.
Qingdao Epic Powder Machinery Co., Ltd is a manufacturer specializing in the production of powder processing equipment. Surface coating equipment is one seres of our products, it includes: pin-mill modifier, turbo-mill modifier and three-roller-mill modifier.
Our main products include:
– Mills: ball mill, валковая мельница, air classifier mill(ACM), jet mill, turbo mill and impact mill, etc.
– Classifiers: include four series of air classifiers: ХТС, ITC, MBS and CTC.
– Surface coating modifiers: pin-mill modifier, turbo-mill modifier and three-roller-mill modifier, etc.
– Auxiliary equipment: control cabinet, belt conveyor and bucket elevator, etc.
– Customers can customize products according to actual needs. One customer, one design.
If you are interested in surface coating equipment or other products from Qingdao Epic, contact our staff directly, we are always at your service.
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