Definition
A heated squeegee coater is a type of laboratory coating equipment used to prepare uniform, controllable thickness coatings on the surface of substrates. Its core feature is the integration of heating during the scraper coating process, which allows temperature control of the coating cutter head, substrate platform, or both. The equipment is mainly used to prepare functional coating samples for subsequent performance testing and analysis, and has a wide range of application value in the fields of materials science, new energy, electronics and coating research and development.
How it works:
The working principle of the heated squeegee coater is based on the combination of the squeegee coating method and temperature control. The equipment usually consists of a precision moving platform, a heatable coating bit, a temperature control system, and a substrate fixture. When working, the slurry or liquid to be coated is placed at the front end of the substrate, and the squeegee with the temperature is translated at a constant speed and scraped over the slurry, leaving a wet film of uniform thickness on the substrate. The thickness of the wet film is mainly determined by the gap between the scraper and the substrate (i.e., the coating gap), which can theoretically be described by the following relationship: wet film thickness ≈ coating gap × slurry solids content × coating process transfer coefficient. The main function of the heating function is to change the rheological properties of the slurry, such as reducing viscosity, promoting solvent volatilization or improving film formation, so as to obtain a more ideal coating morphology and microstructure.
Measurement and calibration methods
To ensure the accuracy and repeatability of the coating results, key parameters need to be measured and calibrated. The coating thickness is usually measured immediately after coating with a wet film thickness gauge, or after the coating is completely dry and cured, using a micrometer, profiler, etc. to measure the dry film thickness. The coating speed is verified by the device's built-in encoder or by an external velocimeter. Temperature calibration requires the use of a surface thermometer or thermal imager to confirm the consistency between the actual temperature of the tool head and the platform and the set value. In addition, regularly checking the flatness and parallelism of the scraper and the levelness of the platform are the basic steps to ensure the uniformity of the coating. Relevant process standards should be followed, such as the practical methods mentioned in coating preparation standards such as ASTM D823.
Influencing factors
The coating quality is affected by a combination of process parameters and material properties. Coating gap is a direct parameter that controls thickness, and an increase in gap usually leads to an increase in wet film thickness. The coating speed affects the shear rate, and too fast can lead to uneven coatings or streaks. Heating temperature is a key variable, and increasing temperature will reduce the viscosity of the slurry, which may improve spreadability, but too high may cause the solvent to volatilize too quickly or change the properties of the slurry. The properties of the slurry itself, such as solid content, viscosity, rheological behavior and solvent volatilization rate, play a decisive role in the morphology of the coating. Environmental conditions, such as laboratory temperature and humidity, can also affect solvent volatilization and coating curing processes. There is an interaction between each parameter, and the optimal combination needs to be determined through systematic experiments.
Applications:
Heated squeegee coater is suitable for a variety of R&D and quality inspection scenarios that require the preparation of precision coatings. In the field of new energy, it is used to prepare lithium-ion battery electrode sheets, fuel cell catalytic layers, or photovoltaic functional layer films. In the field of electronic materials, it is used to coat conductive pastes, dielectric layers or flexible electronic functional coatings. In the traditional coatings and adhesives industry, it is used to simulate industrial coating processes and prepare test samples to evaluate adhesion, abrasion resistance, optical properties, etc. In addition, it is often used in the laboratory preparation of composite materials, paper coatings and special functional films. Its value lies in the ability to simulate and optimize the coating process for subsequent large-scale production under small-scale, controllable conditions.
Equipment selection considerations
Choosing a suitable heated squeegee coating machine requires comprehensive consideration of technical parameters and experimental needs. Core parameters include coating width, which determines the size of the sample that can be processed; The coating thickness range should cover the thickness requirements of the target coating; Range of coating speed and control accuracy. The performance of the heating system, such as maximum temperature, ramp-up rate, temperature uniformity, and temperature control accuracy, is critical for heat-sensitive materials or processes that require precise thermal management. The mechanical accuracy of the equipment, such as platform flatness, movement smoothness, and gap adjustment resolution, directly affects the uniformity of the coating. In addition, consider the compatibility of the equipment with the chemistry of the slurry used, whether it is easy to clean and maintain, and safety features such as overheating protection. It is recommended to compare the technical specifications of different models according to the specific material system, coating objectives, and subsequent test requirements, and conduct necessary process tests to verify suitability.