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Powder fluidity test

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Powder Characteristics Analysis Solution - Next Chapter

This measurement method is currently widely used in the market, particularly with a multi-functional particle and powder characteristic analyzer such as the FT-2000A. It is also considered one of the most intelligent instruments available today, often used for paper writing, corporate quality control, or higher-level recognition.

For your reference, this device provides reliable data that can be crucial in various industrial applications.

3.2 Shearing Method

The shearing method is a relatively advanced technique, commonly used in European and American countries with a long industrial history. It focuses on describing the intrinsic properties of bulk solid materials, such as internal friction and wall friction, and is especially useful for analyzing powder flow characteristics.

The Jenike method involves using a ring shear apparatus to analyze the flow behavior of powders and establish a data model. Combined with PC software, it allows real-time dynamic analysis of powder shearing, consolidation, time, stress, strain relationships, yield strength functions, Mohr's circle damage envelope, flow factor, effective internal friction angle, yield trajectory, and flow function.

The Jenike Liquidity Index (FI) is used to determine whether the powder flows or not and identify critical points. It also helps calculate the hopper half-angle, powder void ratio, and the relationship between looseness and compaction.

In my opinion, this method is more suitable for research institutions, universities, or large enterprises with strong technical capabilities. The complexity of the analysis and the need for theoretical knowledge make it difficult for non-experts to fully master. However, when applied in large companies or academic settings, it offers high reliability and predictive power, especially in the design of powder processing equipment.

3.3 Drum Method

The drum method involves filling a drum with powder particles and rotating it slowly. The number of collisions per revolution at a fixed speed is measured. A higher collision count indicates better fluidity, while a lower count suggests poor flowability. This method reflects the stability, critical transition, and collapse scale of particle flow, as well as mass flow rate.

It meets the requirements of the European Pharmacopoeia. The surface of the particles in the drum can be divided into three areas: sparse flow, dense flow, and creep zones. The shear rate significantly influences the flow characteristics and motion state of the particles.

The movement within the drum has distinct features, typically divided into a flowing surface layer and a stationary bottom layer. As particles transition from a stationary state to flow and then to blockage, the process is organically unified. By adjusting the drum’s rotational speed, the flow and flow state of the particles can be analyzed.

According to the thickness of the flow layer or the free surface inclination angle, the shear rate of the fluidized layer is determined, which helps calculate the fluidity of the particulate material. The shear deformation rate in the dense flow region varies linearly with different rotational speeds and drum diameters, influenced by factors like particle size, shape, friction, and flow conditions.

Although this method is less common in China compared to the previous two, its uniqueness lies in the comparative theory. It enhances the efficiency of powder research and development and is more suitable for scientific research than the earlier methods.

One example of a drum method powder flow tester is the FT-7100.

3.4 Yield Strength Method

When particles are compressed, they undergo changes such as initial compression, particle rearrangement, structure formation, elastic and plastic deformation, particle breakage, bond formation, further compaction, and elastic recovery after pressure removal. These processes lead to the destruction and recombination of particle structures, forming new bonds and compressed bodies.

By applying the principal stress required for deformation, the relationship between volume change and pressure of the powder, the relationship between principal stress and density, the relationship between time and yield strength, and the relationship between yield strength and compression height can be analyzed. Empirical equations such as Heckel, Kawakita, and Adams are used alongside regression models to study new powders and develop solid products like drug formulations and process selections.

The FT-3500 is a powder hardness tester that supports these analyses.