Application of Polyurethane Adhesive

1. Polyurethane adhesives for automobiles The introduction of a large number of lightweight metals, composite materials and plastics in new automobile structures has caused the demand for automotive adhesives and sealants to continue to grow. The most widely used polyurethane adhesives in automobiles are mainly single-component moisture-curing polyurethane sealants for assembling windshields, structural adhesives for bonding glass fiber reinforced plastics and sheet molded composites, two-component polyurethane adhesives for interior parts, and water-based polyurethane adhesives. Automotive interior parts are also an area where the amount of adhesives is growing rapidly.

Water-based polyurethane adhesives widely used in automobiles refer to adhesives formed by polyurethane dissolved or dispersed in water. Most water-based polyurethanes are linear thermoplastic polyurethanes. Because their coatings are not cross-linked and have low molecular weight, their water resistance, solvent resistance, film strength and other properties are still poor, and they must be modified to improve their performance. The automotive repair varnish prepared by the hybrid dispersion of polyester and acrylic acid with uretdione and isocyanurate does not require high-speed stirring equipment, is easy to mix together, and has good adhesion properties.

2. Polyurethane adhesive for wood With the sharp decline of forest resources worldwide and the implementation of my country's natural forest resource protection project, the bonding strength and durability of small wood panels require adhesives that are better than the wood itself. The amount of adhesive used has become a symbol of the level of technological development in the wood industry. In the past, most of the wood adhesives used by people were urea-formaldehyde resins, phenolic resins and melamine-formaldehyde resins with formaldehyde as the main raw material. However, due to the presence of free formaldehyde, the product will gradually emit formaldehyde gas to the surrounding during use, causing environmental pollution. The wood processing industry has begun to turn its attention to new environmentally friendly adhesives, polyurethane adhesives, in order to reduce pollution to the environment.

The single-component moisture-curing polyurethane adhesive used in the woodworking industry is liquid and used at room temperature. It usually has high bonding strength, good flexibility and water resistance, and can be bonded to many non-wood substrates (such as textile fibers, metals, plastics, rubber, etc.). The dry and wet strengths of single-component polyurethane adhesives in the test are better than those of phenolic adhesives. Before bonding, applying a hydroxymethylresorcinol (HMR) coupling agent on the surface of the bonding substrate can improve the bonding strength. HMR can enhance the bonding strength of all thermosetting wood adhesives. When the wood surface is pre-coated with HMR coupling agent, the strength and durability of the one-component polyurethane adhesive can meet most of the strict test requirements.

3. Polyurethane adhesive for construction In addition to the advantages of being non-toxic, pollution-free, and easy to use, polyurethane adhesives also have advantages that other adhesives cannot match, namely excellent low temperature resistance, solvent resistance, aging resistance, ozone resistance, and bacteria resistance, which play an important role in the application of building paving materials. It is widely used in elastic rubber mats, hard rubber floor tiles, and laying plastic track sports fields.

The new two-component polyurethane adhesive breaks through the contradiction between the shear strength and peel strength of traditional adhesives, and can make both achieve high use strength at the same time. It shows excellent performance in the bonding of steel plates for construction, with strong bonding and not easy to deform, and the curing speed can be adjusted at room temperature, making the polyurethane adhesive easy to use and widely used. Polyurethane adhesives are widely used in the bonding of PVC materials for construction, sandwich panel production, and building waterproof coatings.

4. Other polyurethane adhesives play an increasingly important role in the bonding of aerospace equipment, protection and restoration of cultural relics, military industry, stationery, medical and health care, etc. due to their excellent bonding properties.