Classification of Polyurethane Adhesives by Curing Methods (Ⅱ)

Two-component Polyurethane Adhesive is the most important category of polyurethane adhesives, which can be used for bonding metals, rubber, plastics, fabrics, leather, rubber-plastic materials, wood, ceramics, glass and so on, and even has a certain bonding strength for difficult-to-stick polyethylene and polypropylene.

 

Two-component polyurethane adhesive, also known as universal polyurethane adhesive, can be divided into solvent-based and solvent-free types, including quick-curing, temperature-resistant, antifreeze, reinforced and flexible products. The main component of two-component polyurethane adhesive is hydroxyl component, which contains hydroxyl-terminated polyester and polyurethane prepolymer, and the curing agent contains free isocyanate groups. Some main agents are isocyanate-terminated polyurethane prepolymers, and curing agents are polyols or polyamines with low molecular weight. The components A and B are stored separately and mixed in proportion before use.

1. Because it contains urethane bond, it belongs to reactive adhesive. After the two components are mixed, a cross-linking reaction occurs to produce a cured product, which has good initial viscosity, strong adhesion and strong binding force.

2. The dosage of two components can be adjusted widely. As long as the composition and relative molecular weight of raw materials are changed, solvent-free or high solid content adhesives can be made. Generally speaking, the molar ratio of NCO/OH is equal to or slightly greater than L, which is beneficial to complete curing, especially when bonding seals, but it should be noted that NCO components should not be excessive. For solvent-based two-component adhesives, the relative molecular weight of the main agent is large and the initial adhesion performance is good, and the dosage of the two components can be adjusted in a wide range. When the NCO component (curing agent) is excessive, polyisocyanate self-polymerizes to form a tough adhesive layer, which is suitable for bonding hard materials. When the amount of NCO component is small, the adhesive layer is soft and can be used to bond soft materials such as leather and fabric.

3. During preparation, the raw material composition and relative molecular weight of the two-component can be adjusted to make it have proper viscosity at room temperature, and it can be made into a high solid content or solvent-free two-component adhesive.

4. Usually it can be cured at room temperature, and the curing rate can be adjusted by selecting raw materials for preparing adhesives or adding catalysts. Generally, two-component polyurethane adhesive has a large initial adhesion and can be cured by heating, and its final adhesion strength is greater than that of one-component adhesive, which can meet the requirements of structural adhesives.

5. Excellent low temperature resistance, and the bonding strength at low temperature is 2 ~ 3 times higher than that at room temperature.

6. Good flexibility, high peel strength, good impact resistance, vibration resistance and fatigue resistance.

7. Outstanding wear resistance and oil resistance.

8. Good air tightness and electrical insulation.

9. Wide bonding range, capable of bonding a variety of materials.

10. Poor water and damp heat resistance. The heat resistance is not high enough, generally 60 ~ 80℃.