Silica gel is a kind of organosilicon compound, which refers to a compound containing Si-C bond and at least one organic group directly connected with silicon atom. Traditionally, those compounds that connect organic groups with silicon atoms through oxygen, sulfur, nitrogen, etc. Also known as organosilicon compounds. Among them, polysiloxane with siloxane bond (-Si-O-Si-) as the skeleton is the most widely studied and applied organosilicon compound, accounting for more than 90% of the total dosage.
Silicone is mainly divided into four categories: silicone rubber, silicone resin, silicone oil and silane coupling agent.
Silica gel products can be divided into three categories according to different molding processes.
Molded silica gel product
Molding silica gel products are generally made by putting solid silica gel raw materials with vulcanizing agent in, molding with high-temperature mold, pressurizing with vulcanizing machine, and curing with high-temperature sulfur. The hardness of molded silica gel is usually 30℃-70℃. The color of raw materials of mixed color paste is adjusted according to Pan Tong color card number, and the shape of mold determines the shape of molded silica gel product, which is the most widely used product in silica gel industry. Mainly used for silicone industrial accessories, buttons, silicone gift, silicone bracelets, silicone watches, key bags, mobile phone covers, silicone kitchenware, silicone mats, ice cubes, cake molds, etc.
Extruded silica gel product
Extruded silica gel products are usually made by extruding silica gel with an extruder. Generally, the extruded silica gel is long and tubular and can be cut at will. However, the shape of extruded silica gel is limited, and it is widely used in medical devices and food machinery.
Liquid silica gel product
Liquid silica gel products are made of silica gel by injection molding. The product is soft, and the hardness can reach10 C-40 C. Because of its soft characteristics, it is widely used in simulating human organs and medical silicone chest pads.
Special silica gel products
Special silica gel products are made according to the chemical characteristics of silica gel or by adding some auxiliary materials. Special silica gel products can also have high temperature resistance (up to 330 degrees), food grade (completely in line with FDA and LFGB standards), medical grade and flame retardant grade. By adding auxiliary materials, they can also have the characteristics of luminescence, negative ions, discoloration and so on.
Silicone performance
The basic structural unit of silicone rubber products is composed of siloxane chains, and the side chains are connected with other organic groups through silicon atoms. Therefore, the structure of silicone products contains both "organic groups" and "inorganic structures". This special composition and molecular structure make it have both the characteristics of organic matter and the functions of inorganic matter. Compared with other polymer materials, silicone products.
The most outstanding performance is:
1. Temperature resistance characteristics
Silicone products have silicon-oxygen (Si-O) bond as the main chain structure. The bond energy of C-C bond in siloxane is 82.6 kcal/mol, and that of Si-O bond is 65,438+0,265,438+0 kcal/mol. Therefore, silicone products have high thermal stability, and the chemical bonds of molecules will not break or decompose under high temperature (or radiation irradiation). Silica gel is not only resistant to high temperature, but also to low temperature, and can be used in a wide temperature range. The chemical properties and physical and mechanical properties do not change much with temperature.
2. Weather resistance
The main chain of silicone products is -Si-O-, and there is no chemical bond, so it is not easily decomposed by ultraviolet rays and ozone. Silicone has better thermal stability, 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 performance, and their dielectric loss, voltage resistance, arc resistance, corona resistance, volume resistance coefficient and surface resistance coefficient are among the best among insulation materials, and the electrical performance is less affected by temperature and frequency. Therefore, they are a kind of stable electrical insulating materials, which are widely used in electronic and electrical industries. Silicone not only has excellent heat resistance, but also has excellent water repellency, which ensures the high reliability of electrical equipment under wet conditions.
4. Physiological inertia
Polysiloxane compounds are one of the most inactive compounds known. They are very resistant to biological aging, have no rejection with animals, and have good anticoagulant properties.
5. Low surface tension and low surface energy
The main chain of silicone is very flexible, and the intermolecular force is much weaker than that of hydrocarbons. Therefore, compared with hydrocarbons with the same molecular weight, it has lower viscosity, weaker surface tension, smaller surface energy and stronger film-forming ability. This low surface tension and low surface energy are the main reasons for many applications: excellent properties such as hydrophobicity, defoaming, foam stability, anti-sticking, lubrication and glazing.
Use of silicone rubber
Because of these excellent properties, silicone has a wide range of applications. it
It is not only used as a special material for aviation, cutting-edge technology and military technology departments, but also used in various departments of the national economy. Its application scope has been extended to: architecture, electronics and electricity, textiles, automobiles, machinery, leather and paper, chemical industry and light industry, metals and coatings, medicine and medical treatment.