Definition
A Baker applicator is a laboratory tool used to prepare wet films with a specific thickness on a flat substrate. It is typically constructed from precision-machined metal strips with a gap of a specific depth in between. When the tool is dragged at a uniform speed, the fluid material such as paint, ink, or coating is scraped into a uniform wet film, the thickness of which is primarily determined by the clearance height.
How it works:
The Baker applicator works on the basis of gap scraping. The main body of the instrument is a flat metal frame with support edges on both sides of the bottom, and a precise groove or gap formed by two parallel cutter edges in the middle area. When excess sample is placed on the substrate in front of the gap and the applicator is pulled at a constant speed and pressure, the sample flows through the gap. The height of the gap, usually measured in microns or mils, directly determines the thickness of the wet film left on the substrate. Excess sample is scraped off, resulting in a wet film band of fixed width and uniform thickness.
Measurement method
After using the Baker applicator for coating preparation, the wet film thickness is obtained. The relationship between wet film thickness (WFT) and dry film thickness (DFT) can be theoretically estimated by solid volume content (VS), and the commonly used formula is:
DFT = WFT × (VS / 100)
where VS represents the percentage of volume of non-volatile components in the material. The actual dry film thickness needs to be verified directly by using a thickness gauge after the coating is fully cured. During the preparation process, it is necessary to ensure that the applicator is perpendicular to the substrate, and the scraping is completed at a smooth and uniform speed.
Influencing factors
The quality of the coating film is affected by various factors. Operating factors include uniformity of pulling speed, stability of applied pressure, and linearity of operation. Material properties such as rheology, viscosity, and thixotropy can affect the flatness and edge effect of the coating. Environmental conditions such as temperature and humidity may alter sample fluidity or drying speed. The accuracy of the instrument itself, including the machining accuracy of the gap, the flatness and cleanliness of the tool edge, are also key factors. The surface flatness, cleanliness and material of the substrate will also affect the final film forming effect.
Applications:
The tool is widely used in industry and research and development where standardized coating preparation is required. In the coatings industry, it is used to evaluate color, gloss, hiding power, abrasion resistance, and weather resistance. In the field of inks, it is used to test printability, color strength, and drying properties. In the field of electronic materials, it can be used to prepare conductive coatings or optical films. In chemical and material research and development, it is used to study film forming properties, dispersion effects and basic physical and chemical properties of coatings. The samples prepared by it are the basis for a series of subsequent performance tests.
Selection considerations
Choosing the right applicator requires a combination of aspects. The core parameter is the gap height range, which needs to cover the target wet film thickness. Common specification series cater to the needs of thin to thicker coatings. In terms of material, stainless steel is commonly used for its wear and corrosion resistance. The size selection depends on the desired coating width and substrate size. For special samples, models with special clearance designs such as gradient heights can be considered. When selecting a model, you should refer to the relevant industry standards for testing methods to ensure that the accuracy and specifications of the instrument meet the standard requirements. The ease of routine maintenance, such as the ease of cleaning, should also be taken into account.