Definition
A coating preparer is a laboratory tool used to prepare uniform, controllable thickness wet film coatings on the surface of a flat substrate. It uses mechanical scraping to spread liquid samples (such as coatings, inks, adhesives, etc.) into a wet film of a specific thickness for subsequent drying, curing, and performance testing. This equipment is a key part of the pre-treatment for the evaluation of the physical and chemical properties of coatings.
How it works:
The coating film preparer works on the gap scraping principle. It is mainly composed of a precision-machined scraper and a base, and a fixed gap is formed between the scraper and the base through a spacer or step structure. When an appropriate amount of sample is placed at the front of the substrate and the scraper is pushed at a constant speed, the sample is sheared and spread in the gap between the scraper and the substrate, forming a wet film with the same thickness as the gap height. The thickness of the wet film can be controlled by replacing the scraper of different specifications or adjusting the gap, and the theoretical model can be simplified as follows: the thickness of the wet film is approximately equal to the height of the physical gap between the squeegee and the substrate.
Measurement method
After the coating is prepared using the coating preparer, the thickness of the wet or dry film needs to be measured to verify the preparation effect. Wet film thickness can be measured in contact immediately after scraping using a wet film thickness gauge. The dry film thickness needs to be determined by non-destructive or micro-damage methods such as magnetic thickness gauge, eddy current thickness gauge or microscopic cross-sectional method after the coating is completely cured. Measurements should be taken at multiple points at different locations in the film layer to assess uniformity. All measurement methods must comply with relevant international or national standards, such as ISO and ASTM specifications for coating thickness measurement.
Influencing factors
The uniformity and accuracy of coating film preparation are affected by multiple factors. The scraping speed is an important factor, too fast may lead to discontinuity of the film layer, and too slow is easy to cause sagging. The rheological properties of the sample, such as viscosity and thixotropy, directly affect the spreading behavior and flatness of the film. Environmental conditions, including temperature and humidity, can alter sample fluidity and drying rate. The surface flatness, cleanliness and material of the substrate can also affect adhesion and the appearance of the film. The proficiency of the operator and the maintenance status of the preparer, such as the integrity and cleanliness of the blade edge, cannot be ignored.
Applications:
Coating film preparers are widely used in industrial R&D and quality control processes that require standardized coating samples. In the coatings industry, it is used to prepare samples for testing weather resistance, adhesion, hardness and color. In the field of inks, it is used to evaluate printability and color performance. In the adhesive industry, it is used to prepare uniform adhesive layers to test bond strength. In addition, it is also used in the preparation of functional coating specimens in the study of electronic materials, nanocoatings, textile treatments and anti-corrosion materials. Its application ensures comparability of test results across different laboratories or production batches.
Selection guidance
When choosing a coating film preptor, multiple technical parameters need to be considered. The primary parameter is the thickness range, and the model of the corresponding range should be selected according to the required film thickness of commonly used samples. The scrape width should match the common substrate size or test standard requirements. The material of the preparer should be corrosion-resistant and not easy to deform, usually stainless steel or special alloys. The mode of operation (manual or automatic) depends on the number of samples and the level of repeatability requirements. In addition, consider whether it is easy to clean, whether it is equipped with a leveling function to ensure a flat base, and whether it is compatible with current testing standards. It is recommended to compare the functions of different models according to the actual sample characteristics and test purposes.