Overview
A laboratory film coater is a precision device used to evenly apply coating materials to the surface of a substrate. In the textile sector, it is mainly used for small-batch sample preparation, process development and quality control. By simulating processes such as scraping and roller coating in actual production, researchers can accurately control coating thickness, uniformity, and adhesion effects, providing key data for optimizing coating formulations and process parameters.
Coating process principle
The working principle of film coating machines is usually based on mechanical scraping. The textile substrate is flat on the substrate with a coating squeegee with adjustable clearance on top. When the quantitative coating slurry is placed in front of the substrate, the scraper moves at a constant speed, and the slurry is stretched into a uniform wet film in the gap between the scraper and the substrate. The thickness of the wet film h, mainly depends on the scraper gap H, the rheological properties of the slurry and the surface properties of the substrate, and the relationship can be approximately expressed as:
h ≈ k · H · (η/σ)n
Among them, η is the viscosity of the slurry, σ is the surface tension, and k and n are the empirical coefficients related to the slurry and substrate. Key operating parameters include scraping speed, pressure, gap width, and dry curing conditions, which are systematically adjusted to the textile material (e.g., woven, knitted, nonwovens) and coating type (e.g., waterproof, flame retardant, conductive coating).
Application in the research and development of textile coatings
In the research and development stage, the film coating machine is mainly used for formula screening and process window exploration. By varying the ratio of polymer resins, crosslinkers, additives (e.g., water repellents, flame retardants), the researchers prepared a series of coating samples, and subsequently systematically evaluated their performance. Typical application processes include substrate pretreatment, coating slurry preparation, coating mechanism preparation, pre-curing, performance testing, and data analysis. This process allows for efficient comparison of film-forming, feel, durability, and functionality of different formulations.
In the quality control process, the coating machine is used to prepare standard test samples to ensure that the coating performance of different batches or raw materials from different suppliers meets the expected indicators. By fixing all process parameters, variables can be effectively isolated, and accurate comparison and monitoring of coating performance can be achieved.
Relevant standards
Samples prepared using the coating mechanism should be systematically tested according to domestic and foreign standards. Common evaluation items include coating thickness, uniformity, adhesion, washability, air permeability, and specific functional properties. The test methods refer to international standards (such as ISO, AATCC) and national or industry standards (such as GB, FZ/T) to ensure the reliability and comparability of the evaluation results. Performance data is a direct basis for optimizing coating formulations and processes.
Operational precautions
During operation, it is necessary to ensure that the substrate is flat and wrinkle-free, the slurry is uniform and free of bubbles, and the ambient temperature and humidity are stable. Regular calibration of squeegee clearance and movement speed is essential. Currently, technological developments tend to be more automated, such as integrated in-line thickness measurement and closed-loop control, as well as the development of coating modules for new environmentally friendly coatings (e.g., water-based, solvent-free coatings), which improve the repeatability of experiments and support green processes.
Key parameters:
| Scraper clearance adjustment range | Common is 0-2000 microns |
| Typical coating speed | 1-100 mm/s |
| Applicable substrate width | Usually no more than 300 mm |
| Coating thickness control accuracy | Up to ±2 microns |
| Commonly used heating methods | Hot air circulation or infrared radiation |
References
Research on the finishing process of waterproof and moisture-permeable coatings of textiles, Journal of Textile Studies, 2018.
Coated Fabric Processing Technology, China Textile Press, 2015.
ISO 3175-2:2010, Textiles — Professional care, drycleaning and wetcleaning of fabrics and garments.
AATCC Test Method 127, Water Resistance: Hydrostatic Pressure Test.