Definition
A multi-sided applicator is a laboratory coating tool, typically made of metal or plastic, with a body containing multiple coating tanks with varying gap depths. The instrument is mainly used to prepare wet film coatings with a specific and uniform thickness on flat substrates for subsequent drying, curing, and performance testing.
How it works:
The working principle of the multi-sided applicator is based on mechanical scraping. The bottom of the instrument is machined with multiple parallel precision grooves, each of which is constant and different in depth. During operation, an appropriate amount of sample is placed at the front end of the substrate, the applicator is perpendicular to the substrate and scraped at a constant speed and pressure, and the groove controls the amount of wet film material trapped on the substrate, so as to form a series of wet film strips of different thicknesses parallel to each other. The thickness of the wet film mainly depends on the depth of the groove used.
Measurement method
After the coating is prepared using the multi-sided applicator, the key measurement object is the wet film thickness. The wet film thickness is theoretically estimated by the groove depth immediately after coating, and the formula can be expressed as:
h ≈ d
where h represents the thickness of the wet film, and d represents the depth of the groove on the specific surface used by the applicator. The actual thickness will be affected by factors such as material rheological characteristics and scraping speed, so it is often necessary to use a thickness gauge to measure and verify the dry film thickness after the coating is dry, and evaluate the coating uniformity through the conversion coefficient.
Influencing factors
Coating quality is influenced by various factors. Operating factors include scraping speed and applied pressure, and uneven speeds or pressure fluctuations can cause inconsistent film thickness. Material factors involve the viscosity, leveling, and thixotropic nature of the sample, with high-viscosity materials potentially underfilling and low-viscosity materials producing flow. Environmental factors such as temperature and humidity can affect the volatilization rate of solvents and the fluidity of materials. The surface flatness, cleanliness and material of the substrate also have a direct impact on the adhesion and uniformity of the coating.
Applications:
Multi-sided coaters are widely used in industrial and scientific research where systematic evaluation of coating properties is required. In the coatings industry, it is used to compare the gloss, color, hardness and corrosion resistance of different formulations at different thicknesses. In ink research and development, it is used to test printability and hiding power. In the field of functional thin film materials, it is used to prepare samples of gradient thickness to study their electrical or optical properties. In addition, it is also often used in product development and quality control in industries such as adhesives, cosmetics and electronic pastes.
Key points of selection
Multiple technical parameters should be considered in the selection. The range and quantity of groove depth need to match the target thickness test requirements, and the common groove depth gradients are linear increment and nonlinear design. In terms of material, stainless steel has good wear resistance and is suitable for most materials; Plastic material has less risk of damage to the substrate. Precision is key, and attention needs to be paid to the machining tolerance of the groove depth. The width of the instrument should be greater than or equal to the width of the commonly used substrate. Design details such as ease of cleaning, edge sharpness, and the presence of a leveling device are also considered to ensure ease of operation and reliable results.