Definition
A vacuum adsorption scraper coating machine is a laboratory coating equipment used to prepare uniform, controllable thickness films on the surface of a flat substrate. It fixes the substrate through vacuum adsorption and uses a precision scraper system to evenly coat the slurry or liquid onto the substrate, forming a wet film of a specific thickness. This equipment is widely used in sample preparation and pretreatment in the fields of new energy materials, functional coatings, electronic ceramics, optical films and composite materials, and is a key tool for laboratories to conduct coating process research, formula screening and quality control.
How it works:
The working principle of the vacuum adsorption scraper coating machine is based on the technology of combining mechanical scraping with negative pressure fixation. The main body of the equipment typically contains a flat vacuum adsorption platform, a precision scraper system with adjustable height, and a control unit. When working, the substrate is placed on the adsorption platform, and after starting the vacuum pump, the micropores on the surface of the platform generate negative pressure, which firmly and flatly adsorbs and fixes the substrate, effectively avoiding the movement or wrinkling of the substrate during the coating process. Subsequently, the slurry to be coated is placed on the substrate in front of the scraper, and the squeegee is translated at a constant speed by a motor, and the gap between the edge of the scraper and the substrate determines the thickness of the wet film. After the scraper passes, the excess slurry is scraped off, leaving a uniform wet film coating. The thickness of the wet film H can be estimated by the scraper gap G, slurry characteristics and process parameters, and the relationship can be approximately expressed as: H ≈ k · G, where k is the coefficient related to the rheological properties of the slurry.
Measurement and calibration methods
To ensure the accuracy and repeatability of coating thickness, the equipment needs to be systematically measured and calibrated. Key measurements include the uniformity of the scraper gap, the straightness and velocity stability of the scraper movement, and the flatness of the vacuum adsorption. Squeegee clearance is typically measured using a standard feeler gauge or laser micrometer at multiple points in the direction of the squeegee's length, ensuring that its deviation is within the allowable range. The scraper movement speed can be verified by encoder feedback in combination with a timer. Direct measurement of coating film thickness is performed after the wet film has dried or cured, and common tools include micrometers, film thickness gauges, or profilers. During the calibration process, a standard viscosity reference slurry should be used to coat the film on the standard substrate, measure the actual dry film thickness and compare it with the set value, and adjust the equipment parameters or establish a compensation curve if necessary.
Influencing factors
The uniformity of coating quality and thickness is affected by multiple factors. Equipment factors include scraper accuracy, hardness, edge condition, and uniformity of vacuum adsorption. Process parameters such as scraper speed, coating angle, and clearance settings directly affect the shear rate and film thickness. The slurry properties are crucial, and the viscosity η, rheological behavior, solid content and particle size distribution determine the spreadability and defect formation tendency of the coating. Environmental conditions such as temperature and humidity will affect the viscosity of the slurry and the volatilization rate of the solvent. The surface energy, roughness and flatness of the substrate will also affect the wetting and adhesion of the slurry. These factors are interrelated, and the optimal process window needs to be determined through systematic experiments.
Applications:
Vacuum adsorption squeegee coating machines play an important role in a number of industrial and scientific research fields. In the field of new energy, it is used to prepare lithium-ion battery electrodes, fuel cell catalytic layers and photovoltaic films. In the field of electronic materials, it is used to coat dielectric layers, conductive coatings, and functional layers of flexible circuits. In the field of optics and display, it is used to prepare anti-reflection films, filters and display panel coatings. In the field of traditional materials, it can be used to prepare ceramic green strips, special paper coatings and composite prepregs. The samples prepared can be used for subsequent performance tests, such as electrochemical properties, optical properties, mechanical strength and durability evaluation.
Selection considerations
Choosing a suitable vacuum adsorption scraper coating machine requires comprehensive consideration of research needs and equipment performance. The core parameters include the maximum coating width, scraper adjustment range and accuracy, scraper movement speed range and control mode. The vacuum adsorption system should ensure sufficient adsorption and uniformity to suit substrates of different sizes and materials. The equipment material should be corrosion-resistant and easy to clean. The degree of automation, program storage capacity and human-computer interaction interface of the control system affect the convenience of operation. In addition, equipment scalability needs to be considered, such as whether it supports heating platforms, online thickness monitoring, and other optional modules. Supplier technical support, calibration services and spare parts supply are also factors that guarantee long-term use. It is recommended to test the equipment or evaluate the actual coated sample according to the main coating material system and the target film thickness range to verify its suitability.