Definition
An adjustable wet film applicator is a laboratory tool used to prepare uniform, thickness-controlled wet coatings on the surface of a flat substrate. It typically consists of a precision-machined coating scraper and a mechanism that adjusts the gap to control the thickness of the wet film after coating by setting the gap between the squeegee and the substrate.
How it works:
Its core working principle is based on gap coating technology. During operation, an appropriate amount of fluid to be measured is placed at the front end of the substrate, and the applicator scrapes over the surface of the substrate at a constant speed. The precise gap formed between the coating squeegee and the substrate plane determines the thickness of the wet film that remains on the substrate after the fluid passes through. Its basic relationship can be expressed as:
h = g
Among them,h represents the thickness of the wet film,g Represents the clearance value set by the coating scraper. The premise of this relationship is that the fluid is Newtonian fluid and the coating process is in a stable laminar flow state.
Measurement method and operation
Before use, the clearance value should be accurately set according to the thickness of the target wet film through the fine-tuning device on the side of the instrument, and the thickness gauge should be used to calibrate. When coating, ensure that the substrate is horizontally fixed and that a sufficient amount of specimen is placed at the beginning of the coating. When pushing the applicator, the speed should be uniform and the force should be stable, and the scraping action should be completed at one time, without pausing in the middle. The wet film can be visually evaluated immediately after coating, or the dry film thickness can be further measured after it has cured to calculate the conversion rate.
Influencing factors
The accuracy and uniformity of wet film thickness are affected by multiple factors. The instrument's own factors include the straightness and finish of the scraper edge, the accuracy and repeatability of the gap adjustment mechanism. Operating factors include uniformity of scraping speed, applied downforce, and flatness of the substrate. The rheological properties of the fluid material are the key factors, and the viscosity, thixotropy, yield value, etc. of the fluid will affect the final film formation effect, which may deviate from the theoretical thickness of the set gap.
Main application areas:
The instrument is widely used in the research and development and quality control of coating materials. In the coatings industry, it is used to prepare samples for testing the properties of paint films. In the field of printing inks, it is used to evaluate the color, coverage and leveling properties of inks. In the adhesive industry, it is used to prepare adhesive layers of specified thicknesses to test bonding properties. In addition, it is a common tool for preparing experimental samples in many industrial research fields such as electronic materials, nanomaterial coating, and paper surface treatment.
Key points to consider in selection
Multiple technical parameters should be considered in the selection. The core parameters are the coating width and thickness range, which should be selected according to the common substrate size and the desired film thickness range. The clearance adjustment resolution determines the fineness of the thickness control. The wear resistance and corrosion resistance of scraper materials directly affect the service life of the instrument. At the same time, it is necessary to pay attention to whether the design of the instrument is convenient for thorough cleaning to meet the coating needs of different materials. For high-precision studies, it is recommended to choose a model with a constant temperature or constant speed traction attachment for better control of experimental conditions.