Current status of coating technology for absorbing materials
Currently, common
Coating absorbing materialThe coating process includes scraping, spraying, roller coating, etc. The scraping coating process is relatively simple to operate and has low equipment costs, making it suitable for coating scenarios with low precision requirements and large areas. However, its coating thickness uniformity is difficult to control, which can easily result in thickness deviation and surface unevenness defects. The spraying process can achieve rapid and large-scale coating, and the thickness and uniformity of the coating can be controlled by adjusting the parameters of the spray gun. However, during the spraying process, the scattering of paint mist can easily cause environmental pollution and may also introduce impurities, affecting the quality of the coating. The roll coating process has the advantages of high coating efficiency and good coating uniformity, and is commonly used in continuous production. However, it has poor adaptability to coating complex shaped substrates.
Analysis of the causes of defects and bubble formation
Coating equipment factors
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Scraper wear and accuracy issues: In the scraping process, long-term use of the scraper can cause wear and uneven contact with the substrate surface, resulting in inconsistent coating thickness and defects. In addition, insufficient installation accuracy of the scraper, such as not being parallel to the surface of the substrate, can also cause similar problems.
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Poor atomization effect of spray gun: In the spraying process, the atomization effect of spray gun has a significant impact on the quality of coating. If the nozzle of the spray gun is blocked, the air pressure is unstable, or the structure design of the spray gun is unreasonable, it will cause uneven atomization of the coating, resulting in defects such as particle feeling and sagging of the coating, and it is also more likely to carry air and form bubbles.
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Uneven surface condition and pressure of the roller: In the roller coating process, the roughness and flatness of the roller surface, as well as the uneven pressure distribution between the rollers, can cause fluctuations in coating thickness and even lead to missed coating. Uneven pressure may also push air into the coating, forming bubbles.
Coating characteristic factors
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Inappropriate coating viscosity: The coating viscosity is too high, the flowability is poor, and it is difficult to spread evenly during the coating process, which is prone to defects such as stacking and drawing, and also not conducive to the discharge of bubbles; However, if the viscosity is too low, the coating is prone to flow, resulting in uneven coating thickness, and it is more likely to be entrained in air and form bubbles during coating.
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Surface tension issue: The mismatch between the surface tension of the coating and the surface tension of the substrate can cause a decrease in the wettability of the coating on the substrate surface, resulting in uneven coverage and coating defects. In addition, excessive surface tension can also hinder the rupture and discharge of bubbles.
environmental factor
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Temperature and humidity effects: When the ambient temperature is too low, the curing speed of the coating slows down, prolongs the time for bubble discharge, and increases the possibility of bubble residue; If the temperature is too high, it may cause the coating to dry too quickly and solidify before leveling, resulting in surface defects. If the environmental humidity is too high, moisture may mix into the coating, forming bubbles after coating and affecting the adhesion and curing effect of the coating.
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Dust and impurities in the air: In the coating environment, if the air cleanliness is not high, dust and impurities will fall into the coating, enter the coating during the coating process, form defects, and may also damage the stability of bubbles, making them more prone to residue.
Measures to optimize coating process and reduce defects and bubbles
Equipment improvement and maintenance
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Regularly replace and calibrate the scraper: Based on the wear of the scraper, replace it regularly to ensure its sharpness and surface flatness. At the same time, when installing the scraper, a high-precision positioning device is used to ensure that the scraper is parallel to the substrate surface and the error is controlled within a very small range, in order to improve the uniformity of the coating thickness.
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Optimize the structure and parameters of the spray gun: Select high-quality spray guns and optimize their structure, such as improving nozzle design to achieve better atomization effect. Before spraying, accurately adjust the parameters such as air pressure, flow rate, and spraying distance of the spray gun according to the characteristics of the coating and coating requirements, to ensure uniform atomization of the coating and reduce the occurrence of defects such as particle sensation and sagging.
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Maintenance and adjustment of rollers: Regularly check the wear condition of the roller surface, and repair or replace rollers with severe wear. Real time monitoring of pressure distribution between rollers using pressure sensors, adjusted through an automatic control system to ensure uniform pressure and avoid coating defects and bubble formation caused by pressure issues.
Paint formula adjustment
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Optimize viscosity control: Adjust the viscosity of the coating to the optimal coating range by adding appropriate diluents or thickeners. At the same time, studying the viscosity changes of coatings under different temperature and humidity conditions, making real-time adjustments to ensure the fluidity and stability of coatings during the coating process.
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Adjust surface tension: Add surfactants to reduce the surface tension of the coating, improve its wettability on the substrate surface, and enable the coating to spread evenly. At the same time, it is necessary to ensure the compatibility between surfactants and other components of the coating, in order to avoid affecting the absorption performance and curing effect of the coating.
environmental control
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Building a constant temperature and humidity environment: Install air conditioning, dehumidifiers, and other equipment in the coating workshop to control the ambient temperature and humidity within an appropriate range. For example, for mostCoating absorbing materialTemperature control at 20-25 ℃ and humidity control at 40% -60% can effectively reduce defects and bubbles caused by temperature and humidity issues.
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Improve air cleanliness: Use air purification equipment such as high-efficiency particulate air (HEPA) filters to remove dust and impurities from the air entering the coating workshop. At the same time, maintain a positive pressure environment in the workshop to prevent external pollutants from entering and provide a clean environment for coating.
Process operation optimization
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Pre defoaming treatment: Before coating, the coating is subjected to pre defoaming treatment, such as vacuum stirring, centrifugal defoaming, etc., to remove bubbles in the coating in advance and reduce the generation of bubbles during the coating process.
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Coating speed and direction control: Reasonably control the coating speed based on the characteristics of the coating and the performance of the coating equipment. If the speed is too fast, it is easy to get sucked into the air and form bubbles, while if the speed is too slow, it will affect production efficiency. At the same time, for some coating processes that are prone to generating bubbles, such as spraying, the coating direction can be adjusted and cross spraying can be used to give more opportunities for bubbles to escape.
The above data is for reference only, and specific performance may vary due to production processes and product specifications.
