Polyurethane adhesives are a type of high-performance and widely used high-molecular bonding materials. Their core functional characteristics stem from their unique chemical structure and adjustability.
1. Outstanding bonding performance and wide applicability
This is the most prominent feature of polyurethane adhesives. Its molecular chain contains highly polar urethane bonds, which can generate powerful van der Waals forces and hydrogen bond interactions with the surfaces of various materials. Therefore, it has excellent adhesion to a wide range of polar materials such as metals, woods, glasses, rubber, and plastics (especially PVC, ABS, etc.). What is even more worth mentioning is that it can achieve good adhesion to non-polar materials that are difficult to bond, such as polyethylene and polypropylene, after surface treatment. This "all-rounder" characteristic enables it to connect materials of different properties, solving many problems in composite bonding.
2. Excellent flexibility and fatigue resistance
Unlike rigid adhesives such as epoxy resin, polyurethane adhesives usually form a tough adhesive layer after curing. Its molecular chain segments are composed of soft segments and hard segments. This microscopic phase separation structure endows it with excellent flexibility and elasticity. Therefore, it can well withstand the stress caused by vibration, shock and thermal expansion and contraction, and has excellent fatigue resistance. It is particularly suitable for structural bonding under dynamic loads or bonding between materials with different coefficients of thermal expansion.
3. Outstanding low-temperature resistance
At extremely low temperatures, many adhesives become brittle and ineffective. However, the glass transition temperature of polyurethane adhesives is very low. They can still maintain good flexibility and bonding strength in a low-temperature environment of minus tens of degrees Celsius and will not become brittle. This feature gives it an irreplaceable advantage in applications such as refrigeration equipment, aerospace, and cold regions.
4. Adjustable physical form and curing method
Polyurethane adhesives offer great flexibility and come in a wide variety of product forms. There are both two-component (which requires mixing and curing) and one-component (including moisture-curing type, hot-melt type, etc.) types. Users can select the most suitable type based on the production process, efficiency requirements and construction conditions. For instance, moisture-curing one-component polyurethane adhesives are easy to apply and suitable for automated production lines. The two-component type can achieve rapid curing, meeting the requirements of high-strength structural bonding.
5. Good comprehensive mechanical properties
In addition to the above features, polyurethane adhesives usually also have high shear strength and peel strength, good wear resistance, and their hardness can be adjusted through formula design, ranging from soft elastomers to hard plastic-like substances.
