Introduction To The Advantages, Disadvantages of Polyurethane Adhesives!

1. Characteristics of polyurethane adhesives

1. Strong adhesion, high initial adhesion, and wide application range. Since -NCO in the molecular chain of polyurethane adhesives can react with a variety of functional groups containing active hydrogen to form interfacial chemical bonds, it has extremely strong adhesion to a variety of materials. It can not only bond porous materials such as foam plastics, ceramics, wood, fabrics, etc., but also a variety of metals, inorganic materials, plastics, rubber and leather, etc. It is an adhesive with a wide range of applications.

2. Outstanding low temperature resistance. At extremely low temperatures, general polymer materials are converted into glassy state and become brittle, while polyurethane adhesives can still maintain a high peel strength even below -250°C, and its shear strength increases significantly as the temperature decreases.

2. Disadvantages and improvement methods of polyurethane adhesives

1. Free isocyanate monomers in polyurethane adhesives are highly toxic. Epoxy polyurethane can be prepared from hydroxyl-terminated polyvalent epoxy compounds and isocyanate-terminated polyurethane prepolymers, and then mixed with polyamine compounds to form polyurethane adhesives. The adhesive combines the excellent properties of epoxy resin and polyurethane, contains almost no free isocyanate monomer, and has a high solids content. Polyurethane adhesives are developing towards water-based and solvent-free environmentally friendly green adhesives.

2. Polyurethane adhesives usually cure slowly at room temperature, and complete curing sometimes takes several days. The use of multi-component compounding can significantly shorten the room temperature curing time and make it more convenient and applicable.

3. The high-temperature resistance of polyurethane adhesive is far inferior to its low-temperature resistance. If used in food packaging composite films, it needs to be retort-resistant. Introducing nanoparticles can significantly improve its heat resistance, tensile strength, shear strength and peel strength, etc. However, the amount of nanomaterials added must be appropriate. If too much is added, the order of the hard segments in some macromolecules may be destroyed. Arrangement will cause the mechanical properties to decrease.