Causes and preventive measures of surface crusting and gel particle formation in polyurethane laminating adhesives

During the use of dry lamination adhesive, the formation of crusts on the surface of the adhesive, the appearance of gel particles and impurities in the adhesive is a common process problem. These foreign substances are carried by the adhesive liquid and applied onto the film surface, causing particle points, sand holes, scratches, directly damaging the appearance of the composite, and also easily causing local delamination and burst points, seriously affecting the product's yield rate. These are the basic hidden dangers that the composite workshop needs to regularly prevent and control.

 

The oxidation of the adhesive liquid in contact with air is the core reason for crust formation. After the two-component polyurethane laminating adhesive is mixed, its activity is extremely high. Long-term exposure without sealing the adhesive bucket, the surface adhesive liquid will react with oxygen and water vapor in the air, quickly curing and forming elastic rubber sheets. Especially when the curing agent is stored separately without sealing, the moisture absorption reaction is faster, and it is very likely to produce flocculent gel and hard rubber blocks, which will be mixed into the adhesive liquid to form impurities.

Improper operation techniques will exacerbate the generation of particles. Excessive single-time adhesive mixing volume, long storage time exceeding the applicable period, continued use of the adhesive liquid after exceeding the expiration date, the adhesive system gradually cross-links and thickens, and precipitates gel particles. The workshop has a lot of dust and poor environmental cleanliness, and dust impurities fall into the adhesive bucket and combine with the adhesive liquid to form hard particles, causing coating defects after application.

 

During daily production, standardized prevention measures need to be implemented. Adhere to the principle of small and frequent adhesive mixing, strictly prohibit the use of expired adhesive liquid, seal the adhesive bucket in time after mixing, reduce the time of exposure to air. Filter the adhesive liquid before use to intercept gel particles and impurities. Keep the adhesive mixing area clean, standardize the storage method of the adhesive, prevent crusts, gel particles and impurities from forming from the source, ensure the adhesive coating surface is clean and flat, and stabilize product quality.