The hottest two-component polyurethane adhesive

Two component polyurethane adhesive

polyurethane structural adhesive

the definition of structural adhesive refers to the adhesive that can withstand large dynamic load, static load and long-term use when applied to the bonding of stressed structural parts. Generally speaking, structural adhesive is used to join metal, plastic, glass, wood and other structural components instead of bolts, rivets or welding. It is an adhesive that can withstand heavy loads for a long time and whose performance can still be trusted

people have long been familiar with epoxy resin adhesives for structures, but the application of polyurethane adhesives for structures is still gradually recognized. Polyurethane is a block copolymer composed of hard and soft segments. Hard segment molecules provide shear, peel strength and heat resistance, while soft segment molecules have impact, impact, fatigue and other characteristics. By adjusting the composition or structure of hard and soft segments, a variety of structural polyurethane adhesives with required strength can be prepared

1. development of structural adhesives

structural polyurethane adhesives have made great progress in the past 20 years since they were used in FRP (fiber reinforced plastics) of automobiles. At present, in addition to being applied in the automotive industry, it is also widely used in water vehicles [for the bonding of FRP deck and hull, SMC (plate model composite) tower, SMC sluice, etc., which have excellent vibration resistance and impact resistance through the implementation of performance management], elevators (the bonding of elevator doors and wall panels), Purification tank (bonding of FRP flanges and diaphragms. Next, we Jinan new era Gold Testing Instrument Co., Ltd. will introduce the installation method of self-adhesive peel strength tester:), baths (bonding of SMC tiles and ceiling tiles), and residential areas (bonding between cement prefabricated parts of exterior decoration materials)

(1) the adhesive of automobile parts was initially successfully used as polyurethane structural adhesive in automobiles by pliogrip of American coolyesr company. It is a solvent-free two-component reactive adhesive, which was used for the bonding of 5mC engine hood of trucks in 1967. Subsequently, GM, Ford, Mack and other companies successively bonded SMC components of large trucks. Then it is expanded to FRP components

Japan imported technology from the United States and modified it. In 1984, Toyota plastic structural parts were bonded with Nissan polyurethane adhesive, and the effect was satisfactory. With the different structure and composition of isocyanate terminated yanqulu main agent and polyol curing agent, it can produce adhesives with different methylated polymers, different viscosities and different sag resistance, while its bonding strength remains unchanged; Its shear strength is equivalent to that of epoxy resin, and it also shows high peel strength

(2) the application of elevator panels the panels used for the walls and doors of elevator rooms have developed in the direction of lightweight and advanced in recent years. Among them, lightweight is achieved by the adoption of high rigidity and light auxiliary materials and the thinness of surface materials. The materials of elevator panels include steel plate with PVC film on the surface (PVC steel plate for short), steel plate, galvanized steel plate, stainless steel plate, non-ferrous stainless steel plate, brass plate, red copper plate, etc. The panel is usually composed of galvanized steel plate or steel plate and other reinforcement materials bonded to the inner part of the surface plate

the requirements of panel on adhesive are as follows: ① it can be applied to various materials, such as steel plate, PVC steel plate, stainless steel plate, galvanized steel plate, etc; ② Peel strength 150n/25mm; ③ Impact strength ＞ 1.98j/cm2; ④ Shear strength 15MPa; ⑤ The failure state is the internal failure of the adhesive; ⑥ Humidity resistance: after being placed in the environment of 60 ℃ and 90% RH for 60 days, its strength retention rate is more than 70%, and it can be dried after moisture absorption and aging, so the recovery of the adhesive is good; ⑦ Excellent creep resistance and fatigue resistance; ⑧ Even the thin plate will not be distorted due to the curing shrinkage of the adhesive; ⑨ It is resistant to baking paint, so the distance between markings is also different from the heat resistance of baking temperature (up to 175 ℃); ⑩ Due to the poor heat resistance of PVC steel plate, the curing temperature is required to be below 80 ℃; ⑩ Curing time is within 20min; ⑩ Suitable for automation

Japan has successfully developed structural polyurethane adhesives and primers for elevator panels. First, the phosphate ester modifier is used as the main component, and a small amount of PVC polymer is added (to improve the moisture resistance), so as to make a primer with the solvent increased by 12.7% year-on-year. Use a spray to spray a thin layer on the surface of the material. After the solvent is dried, coat the adhesive for bonding. The structural polyurethane adhesive is a two-component adhesive composed of polyether polyol and MDI prepolymer

at present, structural polyurethane adhesives can be used not only for bonding plastics and metals, but also for bonding other materials; It can not only be used in automobile assembly, but also has been extended to construction, machinery and other industrial fields. In order to make the structural polyurethane adhesive more competitive, countries are continuing to make a lot of improvement work, such as reducing costs, changing the two-component into one component, further improving the heat resistance and strength, eliminating the direct use of primer, simplifying the construction operations such as glue mixing and extrusion, and enriching the products and crystal grades to adapt to more kinds of bonded materials and applications in more fields

2. synthesis method

the usual preparation method of structural polyurethane adhesives is to first react polyols with excess polyisocyanates to produce isocyanate terminated prepolymers, and then add diamines for chain extension and cross-linking. In the process of chain extension and chain crossing, it actually forms urea chain and biuret structure, so this kind of polyurethane adhesives should be strictly called "polyurea" adhesives

1. Polyurethane polyurea adhesive

the main agent of this structural adhesive is a prepolymer containing NCO group prepared by the reaction of TDI and polyoxypropylene glycol (molecular weight 2000 and 1000). The curing agent is the reaction of anhydride and aromatic amine (acylation of aromatic amine) to produce aromatic amide (curing agent)

the structural polyurethane adhesive is solvent-free, with the characteristics of simple use process and convenient storage and transportation. It can be cured at room temperature or heat. Its adhesive layer has elasticity and high nail shear strength. Therefore, the structural adhesive was applied to the sealing of the wingtip cover of the "dolphin" helicopter rotor, the bonding of metal carbon fiber composites and the repair of components, and satisfactory results were obtained

2. Polyurethane epoxy polyurea adhesive

epoxy resin adhesive has the characteristics of low flexibility, high hardness, high chemical resistance and high shear strength. If it is combined with polyurethane adhesive, the advantages of the two can be used: complementary disadvantages, and it can reproduce an ideal structural adhesive with a certain softness and considerable adhesive strength. Therefore, a lot of research work has been done on epoxy modified polyurethane adhesive abroad. The synthesis principle is that the polyurethane prepolymer containing NCO end group reacts with alcohol containing epoxy group to produce epoxy terminated polyurethane, and the skeleton of the latter has polyurethane characteristics; Crosslinking and curing are completed by the reaction of epoxy group and amine, and polyurea containing amino functional group is generally used. The adhesive layer is polyurethane epoxy polyurea structure