Uses of Inorganic Silica Gel and Organic Silica Gel

Oct 15, 2020

Silica gel can be used as a desiccant and can be reused. Silica gel is a porous material with different particle sizes formed by proper dehydration of silicic acid gel mSiO2·nH2O. It has an open porous structure with a large specific surface (surface area per unit mass) and can adsorb many substances. It is a good desiccant, adsorbent and catalyst carrier. The adsorption of silica gel is mainly physical adsorption, which can be regenerated and reused. Add acid to the alkali metal silicate (such as sodium silicate) solution to acidify it, and then add a certain amount of electrolyte to stir to form a silicic acid gel; or add acid or Ammonium salts can also generate silica gel. Let the silicic acid gel stand for a few hours to age it, then wash it with hot water to remove the soluble salts, dry it at 60-70℃ and activate it at about 300℃ to obtain silica gel. The silicic acid gel is soaked in a cobalt chloride solution and then dried and activated to obtain color-changing silica gel. When it is used as a desiccant, it is blue before absorbing water, and turns red after absorbing water. From the change of color, we can see the degree of water absorption and whether it needs regeneration treatment. Silica gel is also widely used in steam recovery, petroleum refining, and catalyst preparation. Silicone can also be used as a mobile phone case, which has extremely high drop resistance
Organic silica gel
Organic silica gel is an organosilicon compound, which refers to a compound that contains Si-C bonds and at least one organic group is directly connected to a silicon atom. It is customary to use oxygen, sulfur, nitrogen, etc. to make the organic group and silicon Compounds with connected atoms are also regarded as organosilicon compounds. Among them, the polysiloxane composed of silicon-oxygen bond (-Si-O-Si-) as the skeleton is the most numerous, the most researched and the most widely used type of organosilicon compounds, accounting for more than 90% of the total amount. .
Silicones are mainly divided into four categories: silicone rubber, silicone resin, silicone oil, and silane coupling agent.
Silicone products can be divided into three categories according to different molding processes
Molded silicone products
Molded silica gel products are usually molded by high-temperature molds, after putting solid silica gel raw materials added with vulcanizing agents, and applying pressure through a vulcanizing machine, the high-temperature sulfur is solidified. The hardness of molded silica is usually 30°C-70°C. The raw materials are matched with the color paste to adjust the color according to the Pantone color card number. The shape of the mold determines the shape of the molded silicone product. The molded silicone product is the most widely used in the silicone industry. Mainly used to make silicone industrial accessories, buttons, silicone gifts, silicone bracelets, silicone watches, key cases, mobile phone cases, silicone kitchenware, silicone mats, ice trays, cake molds, etc.
Extruded silicone products
Extruded silica gel products are usually formed by extruding silica gel through an extrusion machine. Generally, the shape of extruded silica gel is long and can be cut at will. However, the shape of extruded silica gel has limitations and is widely used in medical equipment and food machinery. use.
Liquid silicone products
Liquid silicone products are molded by injection molding of silicone. The products are soft and have a hardness of 10°C-40°C. Because of their softness, they are widely used in simulating human organs, medical silicone breast pads, and so on.
Special silicone products
Special silicone products are based on the chemical properties of silica gel or the addition of some auxiliary materials. Special silicone products can also have high temperature resistance (up to 330 degrees), food grade (fully comply with US FDA, LFGB standards), medical grade, and flame retardant grade. , By adding auxiliary materials, it can also have luminous, negative ions, discoloration, and other characteristics.
Silicone performance
The basic structural unit of organic silica gel products is composed of silicon-oxygen chain links, and the side chains are connected to various other organic groups through silicon atoms. Therefore, the structure of organic silicon products contains both "organic groups" and "inorganic structures". This special composition and molecular structure make it integrate the characteristics of organic substances and the functions of inorganic substances. Compared with other polymer materials, silicone products
The most prominent performance is:
1. Temperature resistance
Silicone products are based on the silicon-oxygen (Si-O) bond as the main chain structure. The bond energy of C-C bond is 82.6 kcal/mole. The bond energy of Si-O bond is 121 kcal in silicone /Mole, so the thermal stability of silicone products is high, and the chemical bonds of molecules will not break or decompose under high temperature (or radiation exposure). Silicone is not only resistant to high temperatures, but also resistant to low temperatures, and can be used in a wide temperature range. Whether it is chemical properties or physical mechanical properties, the change with temperature is very small.
2. Weather resistance
The main chain of organic silicon products is -Si-O-, there is no double bond, so it is not easy to be decomposed by ultraviolet light and ozone. Silicone has better thermal stability and radiation resistance and weather resistance than other polymer materials. The service life of silicone in natural environment can reach several decades.
3. Electrical insulation performance
Silicone products have good electrical insulation properties. Their dielectric loss, voltage resistance, arc resistance, corona resistance, volume resistivity and surface resistivity are among the best in insulating materials, and their electrical properties are affected by temperature and frequency. The impact is very small. Therefore, they are a kind of stable electrical insulating materials, which are widely used in the electronics and electrical industries. In addition to excellent heat resistance, silicone also has excellent water repellency, which is a guarantee for high reliability of electrical equipment used in wet conditions.
4. Physiological inertia
Polysiloxane compounds are among the most inactive compounds known. They are very resistant to biological aging, have no rejection reaction with animal bodies, and have good anticoagulant properties.
5. Low surface tension and low surface energy
The main chain of organosilicon is very flexible, and its intermolecular force is much weaker than that of hydrocarbons. Therefore, it has lower viscosity than hydrocarbons of the same molecular weight, weak surface tension, low surface energy and strong film-forming ability. This low surface tension and low surface energy are the main reasons for its many applications: hydrophobicity, defoaming, foam stability, anti-sticking, lubrication, glazing and other excellent properties.