Particle size testing is an experimental work that characterizes particle size characteristics of powders by special instruments and methods. Powder is widely used in our daily life and industrial and agricultural production. Such as flour, cement, plastics, paper, rubber, ceramics, drugs and so on. In the different application fields, the requirements for powder characteristics are different, in all the indicators that reflect the characteristics of the powder, the particle size distribution is the most concerned indicator in all the application fields. Therefore, it is a very important work to objectively reflect the particle size distribution of the powder. Let me talk about the basic knowledge and basic methods of granular testing.
First, the basic knowledge of granular testing
1. Particle: A geometry with a specific shape within a size range. The size described here is generally between millimeters and nanometers, and the particles not only refer to solid particles, but also liquid particles such as droplets and oil beads.
2. Powder: A particle group composed of a large number of particles of different sizes.
3, particle size: the size of the particle is called the particle size.
4. Particle size distribution: The percentage of different particle sizes of the total powder reflected by specific instruments and methods. There are two forms of interval distribution and cumulative distribution. The interval distribution, also known as the differential distribution or frequency distribution, represents the percentage of particles in a series of particle size intervals. The cumulative distribution is also called the integral distribution, which represents the percentage of particles smaller than or greater than a certain size.
5. Representation of particle size distribution:
① Table method: The method of listing the interval distribution and cumulative distribution of particle size by using the table method.
② Graphic method: The method of representing the particle size distribution in the form of histograms and curves in the rectangular scale system.
③ Function method: The method of representing the particle size distribution with mathematical functions. This method is usually used in theoretical research. For example, the famous Rosin-Rammler distribution is a function distribution.
6. Particle size and equivalent particle size:
Particle size is the diameter of the particle. This concept is very simple and clear, so what is the equivalent particle size, and what is the relationship between the particle size and the equivalent particle size? We know that only a round sphere has a diameter, and other shapes of geometry have no diameter, and the particles that make up the powder are mostly not round, but a variety of irregular shapes, such as flake, needle, polygonal, and so on. In theory, the size of these complex particles cannot be directly expressed by the concept of diameter. In practice, diameter is the most intuitive and simple quantity to describe the size of a particle, and we hope to use such a quantity to describe the size of the particle, so we introduce the concept of equivalent particle size in the practice of particle size testing.