Basic Knowledge of Polyurethane Adhesives

Polyurethane adhesives are polymer-based adhesive materials containing the characteristic group of carbamate (-NHCOO-) that are produced through a polymerization reaction using isocyanates and polyols as the main raw materials. Due to their excellent comprehensive performance, they have become one of the core products in the high-end bonding field. 

 

From a chemical structure perspective, its molecular chain features both flexible polyether/polyester segments and rigid amine carbonate segments. By adjusting the raw material ratio, molecular weight, and crosslinking density, the performance can be regulated from a soft elastomer to a hard cured body. It possesses high strength and good toughness, and can effectively buffer the thermal expansion differences of different materials, making it suitable for various bonding scenarios with multiple substrates.

 

According to the curing mechanism, the mainstream can be classified into three categories: solvent-based polyurethane adhesives, which contain volatile organic solvents, have high bonding strength and good permeability, but require attention to environmental protection and safety control; solvent-free polyurethane adhesives, which do not contain solvents, are green and low VOC, are suitable for high-speed automated production lines, and are mostly used for soft packaging laminations; moisture-curing polyurethane adhesives, which rely on moisture in the air to complete cross-linking and curing, are single-component and easy to apply, and are commonly used for sealing and bonding in construction and automotive parts. 

 

This adhesive exhibits excellent low-temperature resistance, fatigue resistance, and chemical corrosion resistance. It has good adhesion compatibility with various materials such as metals, plastics, leather, fabrics, and wood. Additionally, it possesses outstanding flexibility and peel strength, and can withstand vibration and impact. 

 

In terms of application, it is widely used in fields such as soft packaging composites, automotive interior and exterior assembly, building energy-saving board bonding, footwear manufacturing, rail transportation, and electronic component packaging. In the development of the industry, it is upgrading towards directions of no solventization, water-based, high solid content, rapid curing, and low odor. At the same time, through modification technology, its heat resistance and adhesive durability are enhanced to meet the strict application requirements of high-end manufacturing.