Selecting polyurethane adhesives is a technical task that requires comprehensive consideration. The core lies in ensuring that the performance of the adhesives precisely matches the application requirements. The following are several key steps:
1. Clearly define the bonding material
First of all, it is necessary to determine the type of material to be bonded (such as metal, plastic, wood, composite materials, etc.) and its surface characteristics (such as polarity, roughness). The requirements for the wettability and adhesion of adhesives vary greatly depending on different materials and surface treatment methods. For instance, when bonding inert plastics such as PP and PE, it is often necessary to select special models specifically designed for difficult-to-bond materials.
2. Analyze the working conditions
This is the decisive factor in the selection. A comprehensive assessment is required of the type (shear, tensile, peel, etc.) of stress that the bonding area will bear, its magnitude, and the environment it is in.
(1)Mechanical properties: High-strength types should be selected for high-load-bearing structural parts. For flexible materials or parts that need to withstand vibration, models with good toughness and high peel strength should be selected.
(2)Environmental tolerance: For long-term outdoor use, attention should be paid to the resistance to ultraviolet rays and damp heat aging. When in contact with water or damp environments (such as automotive interiors, underwater equipment), it is essential to emphasize hydrolytic stability. If it is used in high or low temperature environments, attention should be paid to its working temperature range.
(3)Chemical medium: If there is a possibility of contact with oils, solvents or other chemicals, products with corresponding resistance should be selected.
3. Determine the process requirements
The production process directly affects the selection of adhesive forms (such as two-component, one-component moisture-curing, hot-melt type, etc.).
(1)Two-component: Requires precise mixing, fast curing speed, high strength, and is suitable for factory environments with conditional control.
(2)Single-component moisture curing: It is easy to operate, but the curing speed is affected by the environmental temperature and humidity. It is suitable for on-site construction or gap filling.
(3)Curing conditions: Consider whether the allowable open time, initial fixing time and complete curing time meet the production cycle. Heating can significantly accelerate the curing of certain models.
4. Pay attention to regulations and safety
For specific fields such as food packaging, medical devices, and children's products, products that comply with relevant national or industry safety and hygiene standards (such as FDA, GB, etc.) must be selected. At the same time, assess its volatile matter content and whether it is environmentally friendly and non-toxic.
