Structural adhesive (referred to as structural adhesive) is It refers to an adhesive that is used for bonding stress-bearing structural parts, can withstand large dynamic loads, static loads, and can be used for a long time. In layman’s terms, structural adhesives are high-performance adhesives that are used to bond structural components such as metal, plastic, glass, wood, etc., instead of bolts, rivets, or welding, and can withstand large loads for a long time.
Polyurethane adhesives with high bonding strength and good durability are structural polyurethane adhesives. Some solvent-based two-component polyurethane adhesives can be used as structural adhesives. Many polyurethane structural adhesives are solvent-free, including one-component moisture-curing and heat-curing polyurethane adhesives, and solvent-free two-component polyurethane adhesives.
Structural polyurethane adhesives were originally used in automotive FRP (fiber reinforced plastics). In addition to being used in the automotive industry, they are also widely used in water vehicles (used in Used for bonding FRP decks and ship hulls, as well as bonding SMC composite towers, SMC sluices, etc. These bonding parts have excellent vibration resistance and impact resistance), elevators (elevator doors, wall paneling, etc.) joints), johkasou (bonding of FRP flanges and partitions), bathtubs (bonding of SMC/ceramic tiles, ceiling/ceramic tiles), and residential buildings (bonding of cement prefabricated components of exterior decoration materials), etc.
One preparation method for two-component solvent-free structural polyurethane adhesive is to first react polyol with excess polyisocyanate to prepare isocyanate group-terminated prepolymer as one component, and diamine and its mixture as A component that, when cured, forms polyurethane-urea.
【Example1]
react polypropylene oxide (molecular weight 2000 and 1000) with TDI to prepare NCO-containing Prepolymer, as one component of the adhesive; acid anhydride reacts with excess aromatic amine to form aromatic amide as another component. The two components are formulated into an adhesive at a ratio of 1/1, with a pot life of 40 to 60 minutes. Curing conditions: Curing at around 24℃ for 48h, or 80℃ for 3h. The shear strength of bonded aluminum alloy is 19.7MPa when cured at 80°C and 12.8MPa when cured at room temperature.
The adhesive layer of this structural polyurethane adhesive has elasticity and high shear strength. Therefore, satisfactory results were achieved when this structural adhesive was used for helicopter rotor tip cover sealing, metal/carbon fiber composite material bonding and component repair.
【Example2]
Mixture of low molecular weight polyester polyol and 1,4-butanediol in a certain proportion Nail-forming components. PAPI as component B.
This kind of adhesive is characterized by a high degree of cross-linking and good heat resistance of the adhesive layer. In addition, epoxy resin and polyurethane prepolymer are reacted to obtain a polyurethane prepolymer with terminal epoxy groups, and the other component is an amino-containing oligomer to form an epoxy resin-modified polyurethane structural adhesive.
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