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Powder fluidity test

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Powder Characteristics Analysis Solution - Next Chapter

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

For your reference.

3.2 Shearing Method

The shearing method is considered a relatively advanced measuring technique. It's commonly used in industrialized countries in Europe and America. This method focuses on describing intrinsic properties of bulk solid materials like internal friction and wall friction, particularly when analyzing powder flow behavior.

The Jenike method involves using a ring shear device to analyze the flow characteristics of powders and establish a data model. Combined with PC software, it allows real-time dynamic analysis of 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.

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

In my opinion, this method is more suitable for research institutions, universities, or large enterprises with strong technical resources. The complexity of the analysis requires significant theoretical knowledge, making it challenging for non-experts to master fully. However, it's widely used in large companies and academic settings, offering high reliability and predictability, especially in designing powder equipment.

What is more commonly used in industry today is the Powder Flow Behavior Dynamic Analyzer, such as the FT-3400. It has a high level of intelligence, providing substantial analytical data during the process, making it an excellent choice for researchers.

3.3 Drum Method

The drum method involves filling a rotating drum with powder particles and measuring the number of collisions per revolution at a fixed speed. A higher number of collisions indicates better fluidity, while fewer collisions suggest lower 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 based on the flow rate: sparse flow area, dense flow area, and creep zone. The shear rate change significantly affects the particle flow characteristics and motion state.

The movement of particles in the drum has distinct features, typically divided into a flowing surface layer and a stationary bottom layer. Particles transition from a stationary state to a flowing state and then through a blockage back to a stationary state. By adjusting the drum's rotational speed, different flow states of the particles can be observed.

Based on the thickness of the particle flow layer or the free surface inclination angle in the drum, the shear rate of the fluidized layer can be calculated, which helps determine the fluidity of the particulate material.

The shear deformation rate of particles in the dense flow region varies linearly with rotational speed and drum diameter. Factors such as average shear rate, average shear deformation ability, particle size, shape, friction, and flow conditions all influence these results.

Although this method is less commonly used in China compared to the previous two, its uniqueness lies in the comparative theory. Data analysis from this method can improve the efficiency of powder research and development. It is more abstract than other methods and is better suited for scientific research applications.

One known 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 is removed. These processes lead to the destruction and recombination of the particle structure, forming new bonds and compressed bodies.

Applying the principal stress required for deformation, the yield strength method analyzes the relationship between volume change and pressure, the relationship between principal stress and powder density, the relationship between time and yield strength, and the relationship between yield strength and compression height. Empirical equations like Heckel, Kawakita, Adams, and the North Sichuan equation are used to analyze new powders, develop solid products like drug formulations, and meet compaction density and pressure requirements.

The powder hardness tester FT-3500 is one example of such equipment.