In general, the silicone can be divided according to their nature and composition of organic and inorganic silicone silicone two categories. Shape into its component silicone extrusion and molded silicone .
Inorganic silica is a highly active adsorption material , usually with sodium silicate and sulfuric acid , and after a series of aging process , acid bulbs , etc.
Obtained. An amorphous silica material , its chemical formula is mSiO2. nH2O. Insoluble in water and any solvent , non-toxic , odorless , chemically stable, does not react with any substance except alkali, hydrofluoric acid . Various types of silica are formed in different manufacturing methods of different pore structure . Chemical composition and physical structure of silica gel , and determines that it has many other similar materials difficult to replace characteristics: high adsorption properties, good thermal stability, chemical stability, high mechanical strength.
Silicone is an organosilicon compound containing a Si-C bond means , and at least one organic group is directly bonded to silicon atoms compound , and those on the regular habits through an oxygen , sulfur, and nitrogen, the organic silicon group compound atom is attached as an organic silicon compound . Among them, the silicon- oxygen bond (-Si-O-Si-) for the skeleton consisting of silicones, silicone compounds are the most numerous , most studies , the most widely used class of more than 90% of the total amount .
Extruded silicone relatively common , such as household electric cooker ring , called the rice cooker silicone seals .
Molded silicone bit more complicated , irregular shape, including silicone bowls, silicone ice tray , silicone bakeware and more.
Inorganic silicone
About inorganic silicone
Name: Silicone
Alias: silica gel or silicic acid gel
Name : Silica gel; Silica
MF : xSiO2 · yH2O
Weight: 60.08
CAS Registry Number : CAS # 112926-00-8
EINECS No. :231 -545-4
Word explanation : Chemical Formula xSio 2 · yH2O. Transparent or white granular solid . Has an open porous structure , strong adsorption, can absorb a variety of substances. Dilute sulfuric acid ( or hydrochloric acid ) in an aqueous solution of sodium silicate and allowed to stand , it will become hydrous silicate gel and solid-state technology . Washed with water electrolyte dissolved therein remove Na + and SO4 2 – (Cl-) ions, a silica gel can be dried . As absorb moisture , moisture is about 40% . For gas drying , gas absorption, liquid dewatering , color layer , but also used as catalysts. Such as cobalt chloride , dry blue, and red absorption . Repeated use of renewable .
Safety performance
The main ingredient is silica, silica gel , chemically stable , does not burn . Silica gel is an amorphous silica dust content of the workshop should be controlled less than 10 mg / cubic meter, the need to enhance ventilation, wear a mask when operating .
Silicone has a strong adsorption capacity, can produce human skin drying effect , therefore , the operation should wear good clothes. If the silicone into the eyes , flush with lots of water and seek medical treatment as soon as possible .
Blue silicone because it contains small amounts of cobalt chloride , toxic, should avoid contact and inhalation of the mouth and food , such as the occurrence of poisoning should immediately seek medical treatment.
Silica in the course of the medium due to the adsorption of water vapor or other organic substances , the adsorption capacity decreased after regeneration can be reused.
Security terms :. S22 Do not breathe dust Do not breathe dust.
Silicone regeneration
A reproduction after absorbing silica
Silica gel adsorption of water , thermal desorption way through the water to remove heat in different ways , such as electric heaters , heating and hot flue heat drying . Desorption temperature control in heating 120 – 180 ℃ is appropriate, for the blue gel indicator , color gel , DL -type blue silicone control at 100 – 120 ℃ appropriate. The maximum temperature of various industrial silicone regeneration should not exceed the following limits :
Coarse pore silica shall not exceed 600 ℃;
Pore silica shall not exceed 200 ℃;
Blue plastic indicator agent ( or color gel ) shall not exceed 120 ℃;
Silica-alumina gel shall not exceed 350 ℃.
Silicone regeneration , the general control 2% moisture or less back into use .
Renewable two , silica gel adsorption of organic impurities
⒈ roasting method
For coarse -pored silica gel , gradually warming up to 500 can be placed within the roaster – 600 ℃, after about 6-8 hours to
Particles can be white or brown . Of silica gel pores , the firing temperature should not exceed 200 ℃.
⒉ rinsing method
After the silica gel in the saturated water vapor adsorption heat saturated water immersion rinsing detergent to remove oils or other organic impurities can be combined , dried and then dehydrated by washing water .
⒊ solvent flushing method
According to silica gel adsorption of organic species , the choice of an appropriate solvent adsorbed organic matter dissolved in the silica , silica gel is then heated to remove the solvent .
Third, the silicone should pay attention to the problem of regeneration
⒈ drying regeneration should be careful to gradually raise the temperature , so as not to cause severe drying particles burst, lower recoveries .
⒉ silicone baking for regeneration when the temperature is too high will cause changes in the pore structure of silica gel adsorption effect of significantly reducing the impact value. For blue or discoloration silica gel indicator , desorption regeneration temperature should not exceed 120 ℃, otherwise they will be gradually oxidized color developing agent and lose color effect.
⒊ regenerated by silica gel should generally screened to remove fine particles, so the particles evenly.
Storage and Packaging
Silicone has a strong capacity to absorb moisture and should therefore be stored in a dry place , packaging, between the ground and have a shelf . There packaging drums , drum , cardboard boxes, plastic bottles, polyethylene plastic bags, flexible container bags and so on. During transportation to avoid rain, moisture and sunlight .
The use of inorganic silica
Wide pore silica is generally used as a catalyst carrier, a matting agent , abrasive toothpaste . Therefore, different varieties should be selected depending on the purpose.
Silica gel desiccant can be used for , and can be reused. Silica is silica gel mSiO2 · nH2O made suitable dehydrating porous materials of different particle sizes . An open porous structure having a specific surface area ( surface area per unit mass ) is large , many substances can be adsorbed , is a good desiccant, an adsorbent and a catalyst carrier. Silica gel adsorption is mainly physical adsorption, can be regenerated and used repeatedly. Adding an acid to an alkali metal silicate ( such as sodium ) solution, and acidified , and then added with stirring for a certain amount of electrolyte , the silicic acid gel ; acid or sodium silicate solution is added in the thick or silicic acid salts can also generate gel. The silica gel was allowed to stand for several hours so that the aging of soluble salts and washed with hot water at 60 ~ 70 ℃ the dried and activated at about 300 ℃, silica gel can be obtained . The silica gel with cobalt chloride solution and then drying and soaking activation , available color gel . When it is used as a desiccant, is blue before absorption , the absorption becomes red, the color change can be seen from the water absorption degree , and the need for regeneration processing . Silicone is also widely used in the vapor recovery areas , and preparing the oil refining catalyst, etc.
Inorganic silica used as a drying agent , the following aspects may be embodied
1 is mainly used for equipment, instruments, equipment, and other moisture absorption in confined conditions rust .
2 in conjunction with ordinary silica gel desiccant , indicating desiccant to absorb moisture and relative humidity to determine the extent of the environment . As packing silica gel desiccant, widely used in precision instruments , leather, clothing, food , medicines and household appliances.
3 use food-grade silicone because it can be used for baby pacifiers and other supplies in direct contact with the human body , in addition , can also be used to produce silicone skin .
Silicone regeneration should pay attention to the issue
1 , drying regeneration should be careful to gradually raise the temperature , so as not to cause severe drying particles burst, lower recoveries .
2, when the silicone baking regeneration , the temperature is too high will cause changes in the pore structure of silica gel adsorption effect of significantly reducing the impact value. For blue or discoloration silica gel indicator , desorption regeneration temperature should not exceed 120 ℃, otherwise they will be gradually oxidized color developing agent and lose color effect.
3, after the regenerated silica should generally screened to remove fine particles, so the particles evenly.
3 related jargon
Specific surface area : means per g of silica gel has a surface area , including internal and external surface area of the micropores and . – Unit : m / g
Pore volume : Each gram of silica gel inside the pores of the total volume . – Unit: ml / g (ml / g)
Aperture: refers to the internal diameter of the silica pores . – Unit: Angstroms (A 0) or nanometers (nm) 1nm = 10A 0
Adsorption amount : silica gel adsorption at a relative humidity of saturated water vapor , when said amount of the adsorbed amount of adsorption of water vapor . – Unit :%
Bulk density: the quality and volume of the silicone they heap space ratio . – Unit : g / liter (g / l)
PH: PH value is the silica gel after a certain processing conditions , PH value of the aqueous solution containing a proportion of silica gel .
Specific resistance : silica is an indicator of purity . Than the resistance itself is defined as the solution resistance at 1cm distance. Is the specific resistance of the silica gel after a certain processing conditions , the silica gel eluted soluble electrolyte , the electric conductivity than the resistance was measured . Resistance higher than reflected lower water-soluble silica contained in the electrolyte . – Unit : ohm cm (Ω.cm)
Attrition rate : is an indicator of the strength wear-resistant silicone . Refers to silica gel under conditions of loss of abrasion . – Unit :%
Water does not burst rate : is an indicator of the degree of water-resistant silicone water . – Unit :%
4 inorganic silica classification
Silicone based on its pore size is divided into: large pore silica , silica coarse holes , B -type silica gel , silica pores . Due to the different pore structure , adsorption properties so they have their own characteristics . Coarse pore silica gel in the case of high relative humidity has a higher adsorption capacity , pore silica gel in the case of low relative humidity higher than the coarse pore silica gel adsorption , while the B -type silica gel due to the pore structure between the coarse and fine between holes , its adsorption capacity between thick, between pore .
Depending on the use of inorganic silica , silica gel can also be classified into beer , silicone PSA , medical silica gel, indicating silica gel , silica gel desiccant, silica opening agent , such as silica gel toothpaste .
Pores of silica gel
Pore silica gel is colorless or slightly yellow transparent vitreous, its basic quality parameters are as follows : average pitch 2.0-3.0nm, surface area 650-800
M / g, pore volume 0.35-0.4ml / g, the specific heat 0.92KJ/kg. ℃, thermal conductivity 0.63KJ / m. Hr. ℃.
Usage: Apply to dry , moisture, rust . Prevents equipment, instruments, weapons, ammunition, electrical equipment, pharmaceuticals , food , textiles and various other packaging items damp, can also be used as catalyst carrier and dehydration of organic compounds refined . Because of its high bulk density and low humidity absorption effect is obvious characteristics that can be used as an air purifying agent to control air humidity. In the ocean the way there are a wide range of applications , because the goods during transport often deteriorate due to high humidity and moisture , the product can be effective desiccant moisture, so that the quality of the goods is guaranteed . Pore silica is also commonly used in two parallel plates between the sealing window dehumidifier can maintain transparency of the layers of glass .
B -type silica gel
Characters : B -type silica as a milky transparent or translucent pellets or lumps . B -type glue between the pore structure of coarse -pored silica gel , silica pores .
The basic quality parameters : pore volume of 0.60-0.85ml / g, average pore diameter of 4.5-7.0nm, specific surface area of 450-650m2 / g.
Uses: mainly used for air humidity regulators, raw materials and catalyst carriers, pet litter, and as chromatography on silica gel and other chemical products.
Coarse pore silica gel
Coarse pore silica called C -type silicone is a silicone , is a highly active adsorption material , is
Amorphous material , its chemical formula is mSiO2 · nH2O. Insoluble in water and any solvent , non-toxic , odorless , chemically stable, does not react with any substance except alkali, hydrofluoric acid . Chemical composition and physical structure of the coarse pore silica , and determines that it has many other features too difficult to replace similar materials : high adsorption properties, good thermal stability, chemical stability, high mechanical strength.
Coarse pore silica white in appearance , there are massive, spherical and spherical micro three products . Coarse -porous spherical silica and the like is mainly used to remove acid gas purification , drying agents , and the insulating oil ; coarse pore silica gel is mainly used for the catalyst carrier block , drying , gas and liquid purification agents .
5 silicone
Silicone Performance
The basic structural unit of the silicone product is made of a silicon – oxide chain section composed of a silicon atom through a side chain with various other organic groups . Thus, in the structure of organic silicon products containing both ” organic group” , but also contain ” inorganic structure” , this particular composition and molecular structure makes it features organic and inorganic feature set in one. Compared with other polymers, silicone products
The most outstanding performance are:
1 . Temperature characteristics
Silicones are silicon – oxygen (Si-O) bond of the main chain structure , C-C bond energy of 82.6 kcal / mol , the bond energy Si-O bond in the organic silicon is 121 kcal / mole , so the high thermal stability of silicone products , high temperature ( or radiation ) molecular bond is not broken , do not break down . Silicone is not only to high temperature , low temperature resistance, but also can be used in a very wide temperature range . Whether it is physical or chemical properties and mechanical properties, temperature dependence is very small.
2 . Weatherability
Silicones of the main chain is -Si-O-, unparalleled key exists , it is not easy to be decomposed by ultraviolet light and ozone. Better than other silicone polymer material thermal stability and resistance to radiation and weathering capabilities . Silicone natural environment life of up to several decades.
3 . Electrical insulating properties
Silicones have excellent electrical insulating properties , dielectric loss , resistance, voltage, resistance, arc resistance, corona , volume resistivity and surface resistivity of the top in the insulating material etc. , and their performance is affected by temperature and frequency electrical little effect . Therefore, they are a stable electrically insulating material , are widely used in electronics and electrical industry. Silicones have excellent heat resistance in addition , it also has excellent water repellency , the electrical equipment which is used under wet conditions having a high reliability protection .
4 . Physiologically inert
Silicone compounds are known in the least one active compound . They are extremely resistant to biological aging , and animal body without rejection , and has better anti- clotting properties.
5. Low surface tension and low surface energy
Main chain of the silicone is very soft, the force between molecules is much weaker than the hydrocarbon , therefore , lower viscosity than the same molecular weight hydrocarbons , weak surface tension , surface energy is small, the film forming ability . This low surface tension and low surface energy which is the main reason for many applications to obtain : the excellent performance of the hydrophobic , anti-foaming , foam stability, release , lubrication, coating and the like.
Use of silicone
Since these silicones excellent properties , it is very wide range of applications . It
Not only as aviation, cutting-edge technology, special materials used in military technology sector , but also for the various sectors of the national economy , its scope of application has been extended to : construction, electrical and electronics, textiles, automobiles, machinery , leather, paper, chemicals , light industry, metal and paints, pharmaceuticals and medical .
Category 6 silicone
Silicone divided into silicone rubber, silicone resin, silicone three categories.
Depending molding silicone products can be divided into three categories Department
Molded silicone products
Molded silicone products are usually placed in the mold by adding high-temperature vulcanizing agent solid vulcanized silicone raw materials by applying pressure machines, high temperature sulfur of forming a solid , molded silicone hardness is usually 30 ° C-70 ° C. Raw materials in accordance with creams recall Pantone color card color, shape of the mold determines the shape of the molded silicone products , molded silicone products silicone industry is currently the most widely used one . Mainly used only silicone industrial parts, buttons, silicone gifts , silicone wristbands , silicone watches, key cases, mobile phone sets , silicone kitchenware, silicone pad, Ice Cube , cake and so on.
Extruded silicone products
Extruded silicone products usually through extrusion machine extrusion molding silicone , silicone extrusion shapes are generally long , tubular free to cut, but there are limitations shape silicone extrusion , medical equipment, food machinery in a wide range of to use.
Liquid silicone products
Liquid silicone injection molding silicone products through injection molding , product flexibility , hardness can reach 10 ° C-40 ° C, because of its soft features , in emulation of human organs , medical Guijiaoxiongdian , and other widely used.
Specialty Silicone Products
Specialty silicone products is based on the chemical properties of silicone or some add auxiliary materials , specialty silicone products also have a high temperature ( up to 330 degrees ) , food grade ( full compliance with U.S. FDA, LFGB standard ) , medical grade, flame retardant by adding auxiliary materials can also have , luminous , negative ions, color, and other characteristics.
7 Silicone Rubber classified edit
Silicone RTV silicone is mainly divided into high-temperature vulcanized silicone
RTV silicone Introduction and classification
RTV silicone (RTV) is a sixties advent of a new type of silicone elastomer , the most significant feature of this rubber is at room temperature without heating , such as pressure can be cured in situ , extremely easy to use . Thus , came on fast become an important part of the silicone products . Today, RTV silicone has been widely used as adhesives , sealants, protective coatings, potting and molding materials , in all walks of life has its purpose.
RTV silicone its packaging can be divided into single -component and two -component RTV silicone, by curing mechanism can be divided into condensation and molding. Therefore , by component RTV silicone , curing mechanism and the use of technology can be divided into three types, namely single-component RTV silicone, two-component RTV silicone condensation-type and two-component RTV silicone molding added . These three series RTV silicone has its own characteristics : the advantages of one-component RTV silicone is easy to use, but deep curing speed more difficult ; advantages of two-component RTV silicone that hold heat curing , shrinkage is small, no swelling, no stress, curing can be performed on both the inside and the surface, deep cure ; plus RTV curing time mainly depends on the temperature of the silica gel , and therefore , can be controlled by temperature adjustment cure rate .
Among the many synthetic rubber , silicone is a leader in it. It has a non-toxic , tasteless , not afraid to withstand cold temperatures and characteristics , in the ninety degrees below zero Celsius Baidu and ” poised “, ” without blinking an eye ,” still lose the original strength and elasticity. There are good electrical insulation silicone , resistance to oxygen aging resistance , light resistance to aging and mildew resistance , chemical stability. Because of these excellent properties , making silicone get a very broad and important uses in modern medicine . In recent years, the hospitals, research institutes and factories work together successfully trial a variety of silicone medical supplies .
Silicone Earplugs : wear comfortable, noise can be a good barrier to protect the eardrum.
Silicone vacuum extraction device : easy to operate , safe to use , according to the size of the fetal head deformation , fetal scalp will not be sucked up attracting avoid damage to the scalp and intracranial hematoma and other ills , can greatly reduce the pain of childbirth in pregnant women during childbirth .
Silicone artificial blood vessel : a particular physiological function, and the body can be ” intimacy ” , it does not exclude the human body , after a certain time, it will complete with the body tissue is extremely good stability up case .
Silicone tympanic membrane repair piece : its thin, flexible film , finish and good toughness . Is an ideal material for repair of the eardrum , and easy to operate , the effect is quite good.
There are also artificial trachea silica , artificial lung, artificial bone , duodenum silicone tube, the effect is very good.