Gum Arabic Adhesives
Gum Arabic, also known as acacia gum, is the exuded gum liquid from wild trees of the Fabaceae family (specifically, acacia trees). It is named so because it is mostly produced in Arab countries. Gum Arabic is mainly composed of polysaccharides with a relatively low molecular weight and gum arabic glycoprotein with a relatively high molecular weight. Due to its excellent water - solubility, it is very easy to prepare. Neither heating nor accelerators are required. The gum Arabic solution dries extremely fast. It can be used for bonding optical lenses, applying glue to stamps, pasting trademark labels, bonding food packaging, and as a printing and dyeing auxiliary.
Inorganic Adhesives
Adhesives formulated with inorganic substances such as phosphates, phosphates (repeated in the original, might be a typo), sulfates, borates, metal oxides, etc. as binders are called inorganic adhesives. Its characteristics are as follows:
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High - temperature resistance, capable of withstanding 1000 °C or even higher temperatures.
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Good anti - aging property.
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Low shrinkage rate.
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High brittleness. Its elastic modulus is one order of magnitude higher than that of organic adhesives.
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Poor water - resistance and acid - alkali resistance.
Do you know? Besides its adhesive function, adhesives have other uses.
Corrosion prevention: The steam pipes of ships often use aluminosilicate insulation with an asbestos outer layer to achieve heat insulation. However, due to leakage or the generation of condensed water caused by alternating hot and cold conditions, the condensed water accumulates on the outer wall of the bottom - layer steam pipes. Moreover, the steam pipes are exposed to high temperatures and the action of soluble salts for a long time, resulting in severe corrosion of the outer wall. To address this, a water - glass - based adhesive can be used as a coating material on the bottom layer of aluminosilicate to form an enamel - like coating. Its coefficient of thermal expansion is similar to that of the pipe material, with low thermal stress and no cracking. In mechanical installation, components are often fixed with bolts. Devices fixed by bolts are exposed to the air for a long time, which may cause crevice corrosion. During the operation of machinery, bolts may loosen due to intense vibration. To solve this problem, in mechanical installation, the connecting components can be bonded with an inorganic adhesive first, and then connected with bolts. This not only plays a reinforcing role but also has an anti - corrosion effect.
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Biomedical applications: Hydroxyapatite bioceramics have a composition close to the inorganic components of human bone. They have good biocompatibility and can form a strong chemical bond with bone, making them an ideal substitute material for hard tissues. However, the commonly prepared HA implants generally have a high elastic modulus, low strength, and unsatisfactory activity. By choosing a phosphate glass adhesive, the HA raw material powder can be bonded together at a temperature lower than the traditional sintering temperature through the action of the adhesive, thus reducing the elastic modulus and ensuring the material's activity. Cohesion Technology Co., Ltd. announced that they have developed a Coseal sealing glue that can be used for heart bonding and has been successfully applied in clinical practice. Through a comparative use in 21 heart surgeries in Europe, it was found that the use of Coseal in surgical operations significantly reduced surgical adhesions compared with other methods. Subsequent pre - clinical studies have shown that Coseal sealing glue has great development potential in heart, gynecological, and abdominal surgeries. The application of adhesives in the medical field is regarded as a new growth point in the adhesive industry. Structural glues composed of epoxy resin or unsaturated polyester are also used.
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In national defense technology: Stealth submarines are one of the symbols of the modernization of naval equipment. An important method for submarine stealth is to lay acoustic - absorbing tiles on the submarine's outer shell. Acoustic - absorbing tiles are a type of rubber with sound - absorbing properties. To achieve a firm combination of the acoustic - absorbing tiles and the submarine's hull steel plate, adhesives are relied on. In the military field, adhesives are used for tank maintenance, military boat assembly, bonding the thermal protection layers of light bombers and missile warheads, preparing camouflage materials, and for anti - terrorism purposes.
Isn't it amazing? Despite their small size, adhesives involve profound knowledge!
