The application of wet mica powder is very extensive, and only some fields with wide range and special significance are mentioned below. The word "mica powder" in the following refers to "wet mica powder" if there is no explanation ".
The ratio of the diameter to the thickness (diameter-thickness ratio) of the wet mica powder particles (wafer) reaches 80-120 times, and the thickness of the wafer is only about tens of nanometers to one hundred nanometers. This product has a high degree of coverage and UV absorption function, in the film can form an efficient barrier effect, so that corrosive substances in the film diffusion, penetration and migration become extremely circuitous (shielding and labyrinth effect), through the film time extended to 3 times, thereby greatly improving the performance of anti-corrosion coatings. Coatings are generally more concerned with the particle size of the filler and sometimes the whiteness.
1) Barrier effect
Flaky filler in the film to form a basic parallel orientation arrangement, water and other corrosive substances on the film penetration is strongly blocked, in the case of the use of high-quality mica powder (the diameter of the wafer thickness ratio of at least 50 times, preferably more than 70 times), water and other corrosive substances through the film penetration time is generally extended by 3 times. Because the mica powder filler is much cheaper than the seed resin, it has very high technical value and economic value.
In short, the use of high-quality mica powder is an important means to improve the quality and performance of anti-corrosion coatings and exterior wall coatings. During the coating process, the mica wafer is subjected to surface tension before the paint film is cured and lies down, automatically forming a structure parallel to each other and parallel to the surface of the paint film. Such a layer-by-layer arrangement, its orientation is just perpendicular to the direction in which corrosive substances penetrate the paint film, and the barrier effect is most fully exerted. The problem is that the flake structure of mica powder must be perfect. The internal standard of foreign industrial enterprises is that its diameter-thickness ratio should reach at least 50 times, preferably more than 70 times. Otherwise, the effect is not ideal, because the thinner the wafer, the larger the effective barrier area formed by the unit filler amount. On the contrary, if the wafer is too thick, it is impossible to form many barrier layers, while the filler packed with particles has no such effect at all. Also, if the mica wafer is perforated or torn, it will seriously affect the barrier effect (corrosive substances are easy to leak past). The thinner the mica powder wafer, the larger the barrier area formed by the unit filler, the moderate particle size (not to pursue too fine), the better the effect.
2) Improve the physical and mechanical properties of the paint film
The use of wet mica powder can improve a series of physical and mechanical properties of paint films. The key is the morphological characteristics of the filler, that is, the diameter-thickness ratio of the flake filler and the length-diameter ratio of the fibrous filler. The particle-packed filler is like sand and gravel in the concrete, which plays a reinforcing role in the reinforcement.
3) Improve the abrasion resistance of the paint filmCan
The hardness of the resin itself is limited, and the strength of many fillers is not high (such as talc). On the contrary, mica is one of the components of granite, and its hardness and mechanical strength are great. Therefore, adding mica powder as a filler in the coating, its anti-wear performance can be significantly improved. Automotive coatings, pavement coatings, mechanical anti-corrosion coatings, wall coatings and other preference for the use of mica powder, that is the reason.
4) Insulation performance
Mica has extremely high resistance (1012-15 ohm · cm) and is itself the most excellent insulating material. The use of mica powder to improve the insulation properties of the paint film is a well-known technology, so I will not say much. It is very interesting that it is combined with silicone resin or silicone boron resin, when subjected to high temperature into mechanical strength and good insulation properties.CeramicsTherefore, wires and cables made of such insulating materials remain in their original insulating state even after being burned in a fire. This is very important for mines, tunnels, special buildings, special facilities, etc.
5) Flame retardant
Mica powder is a very valuable flame retardant filler, if combined with organic halogen flame retardant, can be made flame retardant and fire retardant coatings.
6) anti ultraviolet, infrared performance
Mica has excellent shielding properties such as ultraviolet and infrared rays. Therefore, adding wet mica powder to outdoor coatings can greatly improve the anti-ultraviolet properties of the paint film and delay the aging of the paint film. Its infrared shielding properties are used in the preparation of thermal insulation materials (such as paint).
7) Reduce settlement
The suspension performance of wet mica powder is very excellent, and very thin tiny wafers can be suspended in the medium for a long time without sedimentation and stratification. Therefore, when mica powder is used instead of the filler which is easy to settle, the storage stability of the coating is obviously improved.
8) Thermal radiation and high temperature coatings
Mica has good infrared radiation ability, such as with iron oxide, can cause excellent heat radiation effect. The most typical example is the application in spacecraft coatings (reducing the temperature of the sunny side by tens of degrees). Many heating of the original coating, as well as the coating of high temperature facilities, need to use a special coating containing mica powder. This kind of coating can work at extremely high temperatures, such as about 1000 ℃, when the steel is already red hot, but the coating is safe and sound.
9) gloss effect
Mica has a good pearlescent luster, so when a large particle size flaky mica powder product is used, it can impart gloss, glitter or reflection to materials such as paints. On the contrary, very fine mica powder can cause repeated mutual reflection in the material, thereby producing a matting effect, and therefore a matting effect when using a small particle size mica powder product.
10) Sound insulation and shock absorption
Mica can significantly change a series of physical moduli of the material, forming or changing the viscoelastic properties of the material. Such materials efficiently absorb vibrational energy and attenuate vibration and sound waves. In addition, vibration waves and sound waves form repeated reflections between mica wafers, which also weakens their energy. Therefore, wet mica powder is also used to prepare noise reduction, sound insulation, vibration reduction coating.
1) Improve the air tightness of rubber
The air tightness of rubber is the primary performance for many rubber products, such as inner tubes, bladders, and many life-saving supplies. In order to improve the air tightness of rubber, in addition to the processing technology and coating technology, it mainly depends on the nature of the rubber itself and its filler. The better the compactness of the rubber, the better the permeability resistance of the article. Of course, this kind of glue is expensive, there is a cost problem, so the use of functional filler wet mica powder, low cost and good effect, its significance is particularly important.
The barrier effect of wet mica powder makes it difficult for harmful substances to enter the material, and it is difficult to diffuse, migrate and penetrate after entering. The principle is similar to that of coatings, I .e. parallel-oriented mica powder wafers block the passage of gas (the penetration time is extended by 3 times).TiresThe inner tube, ball liner and many life-saving equipment is very important. In the specification is not demanding fine, white, but requires a perfect sheet structure.
In short, after adding wet mica powder in the rubber, the air tightness will be greatly improved.
2) Improve the physical and mechanical properties of rubber
The impact resistance, mechanical strength and morphological stability of rubber with large diameter to thickness ratio filler (wet process mica powder) are obviously improved. Wet mica powder can also change the friction characteristics of rubber, different usage of different effects, such as improving the coefficient of friction, or improve the lubrication performance (such as wiper).
After adding the large diameter-thickness ratio filler, the elastic modulus of rubber and other physical properties are greatly improved, which is very important for rubber and other materials.
3) Insulation performance
Mica has an extremely high electrical resistance, and it is well known to use mica powder to improve the insulating properties of the material. One of the uses of rubber is used as an insulating material for wires and cables, and the use of wet-process mica powder is an important means. It should be mentioned that cables used in mines, tunnels and similar situations need to be insulated in case of fire. A special class of insulating materials has been developed abroad, which are composed of silicone rubber (including organic boron resin) and mica powder. This type of insulating material is converted into a ceramic-like substance at the high temperature of a fire, retaining good insulation properties and mechanical strength, allowing the cable to remain insulated in the event of a fire. It should also be mentioned that the iron content will reduce the insulation performance of mica, insulation materials generally should not use dry mica powder.
4) Vibration reduction and sound insulation
Many sound insulation and vibration damping materials use rubber to change the physical properties of the material, such as viscoelasticity, to form the desired effect. Large diameter thickness ratio wet mica powder can change a series of physical modulus of the material. Furthermore, the energy between the wafers (such as vibration waves, sound waves) is reflected, but also absorbs and weakens these energy. Accordingly, mica powder is often added to the "vibration damping sheet" used in vehicles and home appliances. Similarly, many other vibration damping and sound insulation materials also use wet mica powder.
5) Release agent in rubber molding and vulcanization
In many cases, the molding vulcanization of rubber does not use a metal mold or the like, and the performance of the mold release agent directly affects the production. For example, the use of air bags for tire molding vulcanization, such as the use of high-performance release agent, is bound to occur products and mold adhesion, both damage to the mold, but also cause a large number of defective products, the production of great harm.
This kind of release agent often use lubricating grease, silicone, organic fluorine and other materials. Since solid lubricants play an indispensable role in it, modern release agents of this type are generally added to mica powder. Wet mica powder has a perfect flaky crystal shape, the wafer is extremely thin, and the covering ability and isolation ability of the mold surface are extremely high. Moreover, the wafer surface of the wet mica powder is smooth, which can effectively prevent the adhesion between materials. The purity of wet mica powder is high, and the harmful impurity content of rubber and mold bonding is very low, which is very suitable. Impurities such as quartz, feldspar and other mineral powder, which have no flaky structure and rough surface, are one of the important reasons for the difficulty of demoulding. Another reason for the difficulty of demoulding caused by dry mica powder is that the surface of mica particles themselves is very rough, causing adhesion. After adding the wet mica powder, a passage for discharging gas is also formed between the rubber and the mold to prevent the gas from remaining in the gap, thereby improving the appearance of the product.
Similarly, wet mica powder is also a key component of high-grade lubricants (extreme pressure grade lubricants). Wet mica powder can inhibit the migration of rubber additives in the rubber.
The application of wet mica powder in rubber is much more than that. Making full use of the unique properties of wet mica powder, many valuable new rubber products can be developed and many valuable application technologies can be formed.
3 Resin and plastic
1) Change the optical properties of plastics
Mica chip has the functions of reflecting, radiating infrared rays and absorbing and shielding ultraviolet rays. Such as the addition of high-quality wet mica powder in the agricultural film, mica microchip reflects infrared radiation, which can make it difficult for light energy to escape due to thermal radiation (I. e. infrared radiation) after passing through the agricultural film, and improve the thermal insulation effect of the greenhouse and the like. In this application, the purity and flake structure of the mica powder are particularly important. Impurities will reduce the enhancement effect of mica powder, affect the transparency, and make the haze rise greatly, so that the light into the greenhouse is reduced. At the same time, if the sheet structure is poor, the effect of blocking infrared radiation is poor.
Large particle size mica powder filler can improve the luster of the material (pearlescent effect), fine mica powder matting effect.
2) Improve the air tightness of plastics
The wet mica powder has excellent flaky crystal form, the crystallite thickness is measured in nanometers, the diameter-thickness ratio is as high as 80 to 120 times, and the effective barrier area is large. After adding wet high-purity high-quality mica powder into the plastic, the air tightness will be greatly improved. Such plastics, according to the patent literature, can be used to make Coke bottles, beer bottles, pharmaceutical packaging bottles, moisture-proof packaging materials and many similar special plastic packaging materials.
3) Improve the physical and mechanical properties of plastics
The lamellar and fibrous fillers disperse the stresses to which the material is subjected by a mechanism similar to that of reinforcement in concrete. Many reinforcing materials (plastic, rubber, resin, etc.) use anisotropic materials, and the principle is the same. The most typical application is carbon fiber, but carbon fiber is very expensive, coupled with color restrictions, the application is difficult. Asbestos is carcinogenic and its application is strictly limited. The manufacture of ultra-fine glass fibers (such as 1 micron in diameter or nano-scale) has many difficulties and the price is quite high. Particulate fillers include quartz micropowder, kaolin micropowder, etc., which are present in large amounts in dry-process mica powder, like sand in concrete, which has no such effect. Only after adding a large diameter to thickness ratio filler (such as wet mica powder), the tensile strength, impact strength, elastic modulus, other mechanical properties, morphological stability (such as thermal torsion resistance and fatigue creep resistance) and wear resistance of plastics and resins have been significantly improved. There is a lot of research on this in materials science, and one of the keys is the shape ratio of the filler.
Plastics (such as resins) have limited hardness. Many fillers (such as talc) also have low mechanical strength. On the contrary, mica is one of the components of granite, and its hardness and mechanical strength are great. Therefore, the addition of mica powder as a filler in plastics has a particularly obvious reinforcing effect, and the high diameter to thickness ratio is the key to the enhancement of high purity mica powder.
The coupling treatment of mica powder has a great effect on the above applications, which greatly improves the integrity of the material in the chemical sense, so that the performance of the material can be greatly improved. The correct coupling treatment is also the key to the enhancement of mica powder.
Changing the crystallization behavior of the resin is also one of the mechanisms of mica powder enhancement.
The use of high-quality mica powder can make the product more light. This technology can have a very wide range of applications in the plastics industry, such as the manufacture of high-strength products, including plastic parts for machinery and vehicles, geotechnical materials, home appliance housings, packaging materials, household plastic products, films, split wires and ropes, etc.
4) Improve the insulation properties of plastic products
Mica has extremely high electrical resistance and is itself a high-performance insulating material. The use of mica powder to improve the insulation properties of materials is a well-known technique. If you need to manufacture high insulation plastic products, you can consider adding functional filler wet mica powder. As mentioned above, mica with high iron content has low insulating properties and should be avoided. Dry mica powder is not washed, iron content is generally higher, should not use this kind of mica powder.
The application of wet mica powder in plastics is much more than that. Making full use of the unique properties of wet mica powder can develop many valuable new plastic products and form many valuable application technologies. For example, adding mica powder to plastics can improve printing performance and composite bonding performance; SnO precipitation on the surface2Or after metal plating mica powder has conductivity, can be used to make antistatic products and conductive plastics;2After the pearlescent pigment, its application is very much; after coloring is excellent performance pigment; mica can also improve the lubrication performance of the product.
The surface of the sand mold is coated with a formula containing mica powder (including the use of a mold washing agent containing mica powder), which can close the micropores on the surface of the mold, improve the release performance and improve the surface finish of the product.
Used for example in metal compaction. The pressure of metal calendering is very high. If liquid lubricant is used alone, the lubricant on the stress point may be completely squeezed dry, resulting in a "dry friction" state, which is very harmful (mold wear, rough surface of products, rising power consumption, etc.). Adding solid lubricants is an effective solution. Extreme pressure (extreme-pressure) lubricants are also often used solid lubricants to prevent dry grinding state (dry grinding can cause bearing red hot, sintering, the consequences can not be imagined). This kind of mica powder on the wafer surface finish and purity requirements are very high, such as containing quartz sand and other impurities, but accelerated wear.
Mica is a natural mineral product with high chemical stability and is a completely inert substance, so it is safe, non-toxic and harmless, and suitable for cosmetics. Mica wafers have a strong pearlescent luster, especially when the particle size is appropriate, can be used to replace or partially replace expensive pearlescent pigments to enhance the gloss effect of cosmetics. Water can not penetrate the mica chip, used in moisturizing products can inhibit the evaporation of skin moisture.
Mica chip can shield ultraviolet and infrared rays, so it is an excellent cosmetic anti-ultraviolet agent. Because it is purely natural, non-toxic and harmless, it has the advantages that synthetic organic anti-ultraviolet agents do not have. Because the chip is extremely thin and the covering ability is extremely strong, only a small amount of these products are needed to form a layer of anti-ultraviolet protective agent and brightening agent invisible to the naked eye on the skin surface.
The mica particle wafer is extremely thin, the thickness is usually only tens of nanometers, the ratio of the diameter to the thickness of the wafer (diameter to thickness ratio) is as high as 80-120 times, and the hiding power is extremely strong.
7 Special Powder
Mica powder such as surface coated with conductive substances (metal, metal oxide), then the formation of conductive powder, for the production of conductive and antistatic polymer materials. If coated with zinc phosphate, it is the coating anti-corrosion filler.