Features of adhesive

- Dec 14, 2020-

Features of adhesive

Temperature resistance


Temperature resistance is one of the excellent characteristics of inorganic adhesives. Inorganic high temperature adhesives are usually used in the range of 1500 to 1750°C, while the phosphate copper oxide adhesive has a wider temperature resistance range and can be used in the range of 180 to 1400°C. However, the main aggregates used in inorganic high temperature adhesives are zircon sand and refractory clay. The price of zircon sand is relatively high and mainly depends on imports. The refractory clay must be obtained at the expense of land, which is costly. Therefore, it is imperative to find cheap and easily available products to replace traditional aggregates to reduce production costs. Some organic adhesives have also achieved high temperature resistance through modification. For example, phenolic resin glue can withstand high temperatures of 1500°C. The market demand for temperature-resistant adhesives is constantly increasing, so this type of adhesive has broad development prospects.


Low pollution


With the deteriorating global environment, people gradually began to use some environmentally friendly products. Although adhesives are not a huge chemical product, their harm to the environment cannot be ignored. Those non-environmentally friendly adhesives will be gradually abandoned. Polyvinyl formaldehyde adhesive (commonly known as "107 glue") is harmful to human health because it contains free formaldehyde. It has long been banned in developed countries, but because of its low price in China, it still has a considerable market share. However, its usage has gradually decreased and will soon be eliminated. How to change non-environmentally friendly adhesives into environmentally friendly adhesives through modification is an imperative job. Japanese companies have successfully studied a formaldehyde-free adhesive that can replace plywood manufacturing.


Common urea-formaldehyde and melamine adhesives contain formaldehyde that can cause allergic reactions in the human body. The strength, water resistance and cost of this adhesive are similar to those of melamine adhesives. Today, when the voice of environmental protection is increasing, more and more people are beginning to devote themselves to the development of biodegradable adhesives. The biodegradation of polymers is accomplished through hydrolysis and oxidation. Most degradable polymers contain degradable groups in their main chain, such as amine groups, hydroxyl groups, and urea groups. Using dihydroxy to react with ether to synthesize hydroxymethyl-containing polyester as a matrix to produce biodegradable adhesives. They also use hydroxyl-containing butyrate, valerate, cellulose, starch ester, etc. as the matrix, and use sucrose Ester acts as a tackifier to produce adhesives that can be biodegraded or hydrolyzed. In addition, using starch or sulfonated ester as the matrix and adding polar wax to produce polar, water-sensitive adhesives that can be hydrolyzed under the action of water, reducing or eliminating environmental impacts during disposal. Pollution


Non-destructive bonding


The connection of materials mainly includes bolting, riveting, welding and bonding. Although fast connection can be achieved by using bolting and other technologies, the material is damaged due to hollowing out or local heating of the material part, and it cannot be used during use. Avoid stress concentration. In contrast, bonding technology is a non-destructive connection technology, and because the bonding interface as a whole bears the load, the load capacity is increased and the service life is extended.


Lightweight


The density of the adhesive is relatively small, mostly between 0.9 and 2, which is about 20% to 25% of the density of metal or inorganic materials, which can greatly reduce the weight of the connecting material of the adhered object. This has the important value of reducing self-weight and saving energy in aerospace, aviation, missiles, and even automobiles and navigation.


Application


Adhesives can be used in addition to traditional bonding and there are some new and ingenious applications.


Anti-corrosion


The steam pipes of ships mostly use aluminum silicate and asbestos to achieve the purpose of heat insulation. However, due to leakage or alternating cold and heat, condensate is collected on the outer wall of the bottom steam pipe; and the steam pipe is subject to high temperature and soluble salt for a long time. The outer wall is corroded severely. For this reason, water glass series adhesive can be used as the coating material on the aluminum silicate bottom layer to form an enamel-like structure coating. Its thermal expansion coefficient is similar to that of the pipe, and the thermal stress is small, and it will not be cracked. In mechanical installation, components are often fixed by bolts. Devices fixed by bolts are exposed to the air for a long time, crevice corrosion will occur. In the process of mechanical work, the bolts are sometimes loosened due to severe vibration. In order to solve this problem, the connecting members can be bonded with inorganic adhesives in mechanical installation, and then connected with bolts. This can not only play the role of reinforcement, but also play the role of anti-corrosion.