Definition
ISO grinding fineness plate, often referred to as fineness meter or scraper fineness meter, is a physical measuring instrument manufactured according to the relevant standards of the International Organization for Standardization. It is mainly used to evaluate the degree of dispersion and maximum particle size of solid particles in liquid or slurry materials, and its value is indicated in microns. This instrument plays a key role in quality control and R&D in many industrial fields such as coatings, inks, ceramic pastes, cosmetics, etc.
Principle
The core working principle of the instrument is based on the use of precision grooves with a squeegee with a depth gradient. Standard plate surfaces are typically machined with one or two wedge-shaped grooves with uniformly decreasing depth from one end to the other, covering a depth range from 0 to several microns. When measuring, place an appropriate amount of sample at the deepest end of the trench and use a special scraper to scrape it across the entire plate surface perpendicular to the trench direction at a constant speed and pressure. Particles in the sample larger than the local depth of the trench will be dragged out of the visible mark by the scraper, while particles smaller than that depth will pass through smoothly. Observing the position where the scratches began to appear continuously, the calibration depth of the groove was recognized as the grinding fineness value of the sample, which represented the upper limit of the particle size of the significant coarse particles in the sample.
Measurement method
Standard measurement processes require rigorous steps to ensure reproducibility of results. First, ensure that the fineness plate and scraper are clean, dry, and at standard test temperatures. After the sample has been thoroughly stirred, place a sufficient amount on the deeper end of the trench and allow it to fill the trench with a slight surplus. Subsequently, hold the scraper perpendicular to the plate surface and perpendicular to the long side of the groove, and smoothly scrape the sample across the entire length of the trench at a uniform speed within 1 to 2 seconds. Immediately after the scraping action is completed, the scraped surface is observed at a perspective of about 30 degrees under a standard light source and viewing angle. The reading of the scale where the grainy streak or scratch begins to appear uniformly and continuously is the result of grinding fineness, usually averaged by multiple parallel measurements.
Influencing factors
The accuracy of the measurement results is constrained by multiple factors. The rheological properties of the sample itself, such as viscosity and thixotropy, affect the distribution and drag behavior of particles during scraping. Environmental conditions, especially temperature, can alter sample viscosity and plate expansion and contraction. The operator's technique is a key variable, including scraping speed, applied pressure, and the angle of the scraper to the board, and any deviation can introduce errors. The state of the instrument itself, such as the wear of the groove, the flatness and cleanliness of the blade edge, directly affect the measurement accuracy. In addition, the preparation method of the sample, including whether the sampling representativeness and pre-dispersion are sufficient, are also prerequisites that cannot be ignored.
Applications
This instrument is widely used in industrial fields where the quality of particle dispersion needs to be controlled. In the coatings and inks industry, it is used to monitor the degree of abrasiveness of pigments and fillers, which directly affects the gloss, color intensity and stability of products. In the ceramic industry, it is used to test the fineness of glazes and slurries to ensure sintering quality and surface finish. In cosmetics manufacturing, such as liquid foundation and sunscreen, it is used to evaluate the fineness of powder particles, which is related to the skin feel and product quality of use. In addition, it is also a conventional rapid quality control tool in the R&D and production process of dyes, lithium battery pastes, metal pastes and other fields.
Selection considerations
Selecting the appropriate grinding fineness plate requires a combination of measurement needs and standard compliance. The primary basis is the expected fineness range of the sample to be tested, and the common range is 0-25μm, 0-50μm, 0-100μm, and 0-150μm, and the range that covers and is slightly higher than the expected value should be selected. Secondly, it is necessary to confirm the technical standards followed, such as ISO standards, ASTM standards, or national/industry standards, which may differ in groove size, scale index, and material requirements. The material of the instrument is usually hardened stainless steel or precision-polished glass, and its wear resistance and corrosion resistance affect the service life. At the same time, the compatibility and accuracy of the scraper also need to be considered. For specific high-precision or special samples, models with a double-groove design or special surface treatment may also be considered.