The application of polyurethane adhesives in the bonding process is a crucial step that affects the final bonding quality. It requires strict control from multiple aspects such as the environment, equipment, materials, and operation procedures. The following are the main precautions:
1. Environmental and substrate control
The environmental temperature and humidity directly affect the reaction rate and leveling property of polyurethane adhesives. It is generally recommended to keep the environmental temperature within 18-28℃ and the relative humidity below 65%, to prevent the reaction of moisture with the -NCO groups and the formation of bubbles, which may affect the bonding strength. At the same time, the substrate surface must be clean and dry, free of oil stains, dust or other impurities. In necessary cases, corona treatment or primer application should be carried out to enhance the adhesion.
2. Precision of Mixing and Curing
For two-component polyurethane, the mixing ratio must be strictly accurate (with an error generally no more than 2%), and thorough stirring is required to achieve uniformity. The stirring speed should not be too fast to avoid the introduction of excessive air. For single-component wet-curing adhesives, ensure sealing to prevent premature reaction between the prepolymer and moisture in the air. After mixing, pay attention to the operation time limit (shelf life), as exceeding this limit will cause the viscosity of the adhesive to increase, thereby affecting the coating effect.
3. Optimization of Gluing Process Parameters
The coating amount should be precisely adjusted according to the characteristics of the substrate, the composite structure, and the performance requirements. Insufficient coating may result in insufficient bonding strength, while excessive coating is likely to cause overflow, incomplete curing, or waste of resources. The coating method (such as roller coating, scraping coating, or spraying) should be matched with the viscosity of the glue. If necessary, the viscosity can be adjusted by heating or dilution to ensure uniform coating. The speed of the laminating machine and the coating amount should be coordinated to ensure uniform coverage of the glue layer.
4. Equipment Maintenance and Cleaning
The coating equipment (such as mesh rollers, scrapers) should be cleaned regularly to prevent the remaining glue from solidifying and clogging or affecting the coating accuracy. Check if the roller surfaces are worn and ensure the uniformity of coating. After use, thoroughly clean them with the specified solvent (such as ethyl acetate) to avoid the glue from solidifying and damaging the equipment.
5. Safety and Environmental Protection Measures
The
Polyurethane Adhesive contains organic solvents or chemical active components. The operation area should be kept well-ventilated and kept away from fire sources. Operators should wear protective gloves, masks and other personal protective equipment. The waste adhesive and cleaning solvents need to be recycled and disposed of in accordance with regulations to meet environmental protection requirements.
