Definition
An adjustable applicator is a laboratory tool used to prepare samples of wet or dry film with controllable thickness on a flat substrate. It typically consists of a precision-machined tool body with adjustable clearance to control the thickness of the coated liquid by mechanically setting the gap between the squeegee and the substrate. This equipment is widely used in quality control and R&D testing in the fields of coatings, inks, adhesives, electronic materials and chemical raw materials.
How it works:
Adjustable applicators work on the gap coating principle. During operation, the liquid to be measured is placed at the front of the substrate, and the applicator is scraped over the surface of the substrate at a constant speed by manual or mechanical drive. The height of the gap between the scraper and the substrate determines the thickness of the residual liquid film. The clearance height can be fine-tuned with precision threads or gaskets, with a common adjustment range of 0 to 2000 microns. After coating, the liquid forms a uniform film layer during the curing or drying process, and its final thickness is related to the gap setpoint, liquid rheological characteristics and operating conditions.
Measurement method
After the sample is prepared using the adjustable film applicator, the thickness of the film layer needs to be measured and verified. Wet film thickness can be measured at multiple points using a wet film thickness gauge immediately after application, and the average value is used to evaluate uniformity. The dry film thickness needs to be determined by magnetic thickness gauge, eddy current thickness gauge or microscope slicing method after the sample is completely cured. When measuring, points should be taken at different positions of the film layer according to relevant standards (such as ASTM D823, ISO 2808) to ensure data representativeness. Film thickness uniformity can be assessed by calculating the thickness coefficient of variation.
Influencing factors
The quality of the coating film is affected by various factors. Coating speed is an important parameter, too fast may lead to uneven film layer or streaks, and too slow speed can easily cause liquid flow accumulation. The flatness of the substrate directly affects the gap stability, and uneven surfaces can lead to thickness fluctuations. Liquid viscosity affects leveling, high viscosity liquids require large scraping force, and may produce shear thinning effects. Environmental conditions such as temperature and humidity can affect the rate of volatilization and rheological behavior of liquids. The consistency of pressure applied by the operator can also have an impact on film thickness repeatability.
Applications:
Adjustable film applicators have a wide range of uses in industrial testing and research and development. In the coatings industry, it is used to prepare paint film samples to test for adhesion, hardness, abrasion resistance, and gloss. The printing ink field is used to evaluate ink layer coverage, color intensity, and drying performance. It is used in the preparation of electronic materials to make conductive coatings or optical thin film samples. The adhesive industry is used to control the thickness of the adhesive layer to test the bond strength. In addition, it is also commonly used in the research of nanomaterial dispersions, special coatings and functional materials to prepare experimental samples.
Key points of selection
Several technical parameters should be considered when selecting an adjustable film applicator. The gap adjustment range needs to cover the thickness requirements of the sample to be tested, and common models are available in different ranges such as 0-500 microns, 0-1000 microns, and 0-2000 microns. Adjustment accuracy is an important indicator, and high-precision models can reach 1 micron increments. The length of the tool body should match the size of the commonly used substrate, and the common specifications are 100mm, 150mm, and 300mm. In terms of material, the stainless steel blade is corrosion-resistant and easy to clean, and the edge of the carbide scraper has good wear resistance. Some models are equipped with a digital display for precise clearance settings. When selecting, it is also necessary to refer to the specific requirements of relevant industry standards for the preparation of coating films.