Some powders are loose in nature and can flow freely; some powders have strong adhesion and do not flow easily when bonded together. The fluidity of the powder is one of the important properties of the powder and is of great significance for the work of the medicament. For example, powder subcontracting, capsule filling, tablet tableting dosage, etc. are all affected by the fluidity of the powder. (1) The fluidity and expression of the powder The fluidity of the powder is related to the shape, size, surface state, density, porosity, etc. of the particles, and the complex relationship between internal friction and adhesion between the particles, the fluidity cannot be expressed by a single value. . The fluidity of the powder is usually expressed by the angle of repose and the flow rate. 1. Angle of repose refers to the maximum angle that may exist between the free surface of a pile of powder deposited in a horizontal plane and the horizontal plane, that is, the powder is piled up into a "heap" of a cone shape as steep as possible, and the oblique and horizontal lines of the pile The angle of the angle is the angle of repose, which is usually expressed by α. It can be obtained by the following formula. The angle of repose is the easiest way to check the fluidity of a powder. The better the fluidity of the powder, the smaller the angle of repose; the surface of the powder particles is rough, and the greater the adhesion, the larger the angle of repose. It is generally believed that the angle of repose is ≤30o, the fluidity is good; the angle of repose is ≤40o, which can meet the needs of fluidity in the production process; if the angle of repose is ≥40o, the fluidity is poor, and measures should be taken to ensure the accuracy of the sub-dosage. The commonly used measurement methods for the angle of repose include injection method, discharge method, container tilt method, etc., as shown in Figure 5-3. 2. The flow rate refers to the speed at which the powder flows out of a hole or tube of a certain aperture per unit time. The specific measurement method is to open the center of the bottom of the cylindrical container, and the powder is placed in the container, and the amount of powder flowing out per unit time, that is, the flow rate, is measured. Generally, the powder has a fast flow rate, good fluidity, and good flow uniformity. (2) Factors affecting liquidity The fluidity of drugs or excipients is firstly related to their own characteristics. In addition, other characteristics of the powder, such as the size and distribution of the particles, the morphology of the particles, and the roughness of the surface of the particles, also have a significant effect on the fluidity. . 1. Particle size and its distribution It is generally believed that when the particle size of the particles is larger than 200 μm, the fluidity of the powder is good and the angle of repose is small; when the particle size is in the range of 200-100 μm, it is a transitional stage, with the particle size The decrease of the specific surface area of ​​the powder increases, the effect of the friction between the particles increases, the angle of repose increases, and the fluidity deteriorates; when the particle size is less than 100 μm, the adhesion is greater than gravity, and the angle of repose is large. Increased, poor fluidity. The particle size distribution of the powder also has an effect on its fluidity. The powder with larger particle size has better fluidity, but the addition of powder with smaller particle size can make the fluidity worse. The more the amount of fine powder added, the smaller the particle size, the greater the influence on the angle of repose. . Conversely, by adding coarser particles to the fine powder having poor fluidity, the adhesion can be overcome and the fluidity can be improved. 2. Particle morphology and surface roughness Particles are spherical or nearly spherical powder. When flowing, the particles roll more, the friction between particles is small, so the fluidity is better; and the particle shape deviates significantly from the sphere, for example Needle-like or flaky, when the powder is fluid, the friction between the particles is large, and the fluidity is generally not good. Rough surface of the particles also increases the difficulty of flow. Generally, the more irregular the particle shape, the rougher the surface, and the larger the angle of repose, the worse the fluidity. 3. When the moisture content powder is in a dry state, its fluidity is generally good. Since the powder absorbs a certain amount of water in a relatively high relative humidity environment, a water film is adsorbed on the surface of the particles, and the attraction between the particles is increased due to the surface tension of the water, and the fluidity is deteriorated. In a certain range, the amount of moisture absorption becomes larger, and the larger the angle of repose, the fluidity becomes worse. However, when the powder absorbs moisture more than a certain amount, the adsorbed moisture eliminates the adhesion of the surface of the particles and acts as a lubrication, the angle of repose decreases, and the fluidity increases. . The effect of moisture content on fluidity varies with the type of powder. 4. Effect of adding other ingredients Adding other ingredients to the powder sometimes has an effect on fluidity. For example, the addition of talc powder and micronized silica gel to the powder generally improves the fluidity. This material which improves the fluidity of the powder is called a glidant. The JL-A3 powder tester manufactured by Chengdu Jingxin Company can accurately test the angle of repose, fluidity and bulk density of powder. Dinner Plate,Small Dinner Plates,Black Dinner Plates,Square Dinner Sets Guangzhou Concept Home Ltd , https://www.concepthomelimited.com