Important steps in the production of diamond powder - grinding and shaping
At present, the most common diamond powder is produced by grinding, purifying, classifying and other processes of artificial diamond.
Among them, the diamond crushing and shaping process plays an important role in the production of micro powder, and directly affects the shape of the micro powder particles and the content of the target particle size. Different crushing methods will produce different crushing effects. The scientific and reasonable crushing and shaping process can not only quickly crush coarse-grained diamond raw materials (conventional particle size 100-500 microns) into diamond powder particles with a particle size range of approximately (0-80 microns), but also optimize the particle shape. , making the particles of micro powder products more round and regular, reducing or even completely eliminating long strips, flakes, pins and rods and other particles that affect the final quality of micro powder. Maximize the proportion of marketable target particle size output.
In the production of micro powder, the crushing method can be divided into dry method and wet method. Different crushing and shaping methods are used, and their working principles and process parameters are also different.
Process control points of dry grinding method of ball mill
Taking the horizontal ball mill dry grinding method as an example, the main process control points are ball mill speed, ball-to-material ratio, filling coefficient, steel ball ratio, etc. In actual production, they can be flexibly controlled according to different raw materials and the purpose of crushing and shaping.
1. Ball mill speed
The reasonable rotation speed of the ball mill is an important condition for exerting its production capacity. When the diameter of the ball mill barrel is the same. The higher the rotational speed, the greater the centrifugal force generated, and the higher the distance the steel ball is driven to rise along the cylinder wall.
It is generally believed that the suitable working speed of the ball mill is 75%-88% of the theoretical critical speed.
2. Filling coefficient, ball-to-material ratio
In the crushing and shaping process, the appropriate ball-to-material ratio and filling coefficient are crucial. If the ball-to-material ratio and filling coefficient are too high or too low, they will affect the production efficiency and product quality of the ball mill. If the ball-to-material ratio is too high or the filling coefficient is too low, the feeding capacity of a single machine will be restricted.
Practice has proved that for the crushing of diamond raw materials, the loading coefficient is generally 0.45. The ratio of ball to material is 4:1.
3. Steel ball diameter and ratio
In order to crush diamond more effectively, when the ball mill filling coefficient and ball loading amount are determined, steel balls of different diameters should be selected and assembled in proportion to obtain better particle shape and faster crushing and shaping efficiency.
Segmented grinding
In the production process of micro powder, wet crushing is more effective than dry crushing. Because when dry crushing reaches a certain fineness, wall sticking is easy to occur, reducing the crushing effect; with wet crushing, the raw materials always exist in the form of slurry, and it is easy to increase the proportion of fine particle size.
In order to control the particle size ratio, when more fine-grained micro powder needs to be produced, segmented crushing should be used, especially wet segmented crushing is better. This can not only avoid excessive crushing of materials, but also achieve segmentation according to strength during the crushing process.
Jet milling
Another crushing method is the airflow pulverizer crushing method. The airflow pulverizer uses compressed air as the working medium. The compressed air is sprayed into the crushing chamber at high speed through a special supersonic nozzle. The airflow carries the material in high-speed movement, causing the material to move between them. Produce strong collision, friction and shear to achieve the purpose of crushing. Fragmentation occurs when the force acting on the particle is greater than its failure stress. High-speed impact collision causes volumetric fragmentation of particles, while shearing and grinding effects cause surface fragmentation of particles. This crushing method is very beneficial to the production of diamond powder because it can produce ideal particle shapes. The biggest advantage of the airflow pulverizer is that it is not limited by the mechanical linear speed and can produce very high airflow speeds. In particular, the supersonic airflow pulverizer can produce a flow rate several times the speed of sound, so it can generate huge kinetic energy and it is easier to obtain micron-level particles. and submicron ultrafine powders.
Sodium Bicarbonate Dry Desulfurization Process
The dry desulfurization process uses a pulverizer with its own classification system and a conveyor fan combined into a complete grinding and powder spraying device. The pulverized sodium bicarbonate fine powder has a layered or porous structure, uniform particle size, and good dispersion. The solid ultrafine powder is then directly injected into the furnace or reaction tower through multiple nozzles. It can effectively remove more than 95% of SO2 and HCl in exhaust gas, and the removal rate can even reach 99%.
The use of sodium bicarbonate (baking soda) dry desulfurization can not only meet stringent environmental requirements, but also effectively reduce investment and operating costs compared with other flue gas purification methods.
The baking soda dry desulfurization process has the following advantages: fully dry system, no water required; dry powder is sprayed in front of pipes and bags; reaction by-products can be discharged through the dust removal system; no production shutdown is required; one-time investment is very small; and it occupies very little area ; System cost is low; competitive; reaction efficiency is very high, over-injection volume is very small, and undetectable emissions can be achieved; denitration catalyst poisoning is effectively suppressed; flexibility is high, and it can be adapted to the most stringent emission indicators at any time.
Sodium bicarbonate (baking soda, NaHCO3) can be used as an adsorbent for flue gas desulfurization. It removes acidic pollutants in flue gas through chemical adsorption. At the same time, it can also remove some inorganic and organic trace substances through physical adsorption. In this process, sodium bicarbonate fine powder is directly sprayed into the high-temperature flue gas of 140 to 250°C.
In the flue gas pipe, the desulfurizer - baking soda (NaHCO3) - is activated under the action of high-temperature flue gas, forming a microporous structure on the surface, just like popcorn being popped. The flue gas in the flue fully contacts the activated desulfurization agent to undergo a chemical reaction. , SO2 and other acidic media in the flue gas are absorbed and purified, and the desulfurized and dried Na2SO4 by-product enters the bag dust collector with the air flow and is captured.
The newly generated sodium carbonate Na2CO3 is highly reactive at the moment of generation and can spontaneously undergo the following reactions with acidic pollutants in flue gas:
Main reactions:
2NaHCO3(s)→Na2CO3(s)+H2O(g)+CO2(g)
SO2(g)+Na2CO3(s)+1/2O2→Na2SO4(s)+CO2(g)
Side reactions:
SO3(g)+Na2CO3(s)→Na2SO4(s)+CO2(g)
5 major types of surface modification methods for silica
At present, the industrial production of silica is mainly based on precipitation method. The surface of the produced silica contains a large number of polar groups such as hydroxyl groups, which makes it easy to absorb water molecules, has poor dispersion, and is prone to secondary aggregation. problems, thus affecting the industrial application effect of silica. Therefore, most silica needs surface modification treatment before industrial application to improve its industrial application performance.
At this stage, chemical surface modification of silica mainly includes surface graft modification, coupling agent modification, ionic liquid modification, macromolecular interface modification and combined modification, etc. Although each modification process has its own advantages. and characteristics, but currently in industrial applications it is mainly based on coupling agent modification.
The principle of the surface graft modification method is to graft a macromolecular polymer with the same properties as the matrix polymer (such as rubber) on the surface of silica through chemical grafting. On the one hand, it can enhance the interaction between the particles and the matrix. And change the polarity of the particle surface, on the other hand, it can also improve the dispersion of silica itself. It is suitable for grafting polymers with smaller molecular weights. The conditions for grafting polymers with higher molecular weights are harsh.
2. Modification of silica coupling agent
The principle of coupling agent modification is to use some functional groups on the coupling agent to react chemically with the hydroxyl groups on the surface of silica black, thereby changing the group structure and distribution on the surface of silica black to improve compatibility with the matrix. and its own dispersion. Coupling agent modification has the advantages of good modification effect and high reaction controllability, and is currently one of the most widely used modification methods.
3. Silica black ionic liquid modification
Ionic liquids, also called room temperature ionic liquids, are molten salts composed of organic cations and organic or inorganic anions, which are liquid below 100°C. Ionic liquid modification uses ionic liquid modifiers instead of traditional organic phase modifiers to modify silica. Compared with traditional organic phase modifiers, ionic liquid phases are liquid at room temperature, have strong conductivity, and have high stability. It has the advantages of good solubility, non-volatility and low pollution, which is more in line with the requirements of green production, but the modification effect is poor.
4. Interface modification of white carbon black macromolecules
The modifier used in macromolecular interface modification is a macromolecular polymer containing polar groups. During the modification reaction with silica particles, the molecular backbone of the macromolecular interface modifier can be introduced into It has more polar epoxy groups while maintaining the basic main chain structure, thereby improving the compatibility between the silica particles and the matrix and achieving better interface modification effect. This method can synergistically reinforce the matrix with the coupling agent, but the reinforcing effect is low when used alone.
5. White carbon black combined with modification
Combining modification is to modify the combination of silica and other materials, combining their respective advantages to improve the overall performance of rubber products. This method can combine the advantages of two modifiers to enhance the comprehensive performance of the matrix, but the modification effect is closely related to the modifier ratio.
For example, carbon black and silica are both good reinforcing agents in the rubber industry. Carbon black is one of the most commonly used reinforcing agents in the rubber industry. The special structure of carbon black can enhance the tensile and tear strength of rubber materials and Improve its wear resistance, cold resistance and other properties; as a reinforcing agent, white carbon black can significantly improve the rolling resistance and wet slip resistance of rubber products, but its effect alone is not as good as carbon black. A large number of studies have shown that the use of carbon black and silica as reinforcing agents can combine the advantages of both to improve the overall performance of rubber products.
Characteristics And Economic Uses Of Dolomite Mineral
Dolomite crystal is a carbonate mineral of the trigonal crystal system. Its chemical composition is CaMg(CO3)2, often with iron, manganese and other similar isomorphs (instead of magnesium). When the number of iron or manganese atoms exceeds that of magnesium, it is called ankerite or manganese dolomite. Trigonal crystal system, the crystal is rhombohedral, the crystal face is often bent into a saddle shape, and laminated twin crystals are common. The aggregates are usually granular. It is white when pure; gray when containing iron; brown after weathering. Glass luster. It is the main mineral that makes up dolomite. Dolomite originating from marine sedimentation is often interbedded with siderite layers and limestone layers. In lacustrine sediments, dolomite coexists with gypsum, anhydrite, halite, potassium halite, etc.
The word Dolomite is mainly used to commemorate DOLOMIEU (1750~1843), a French chemist. Dolomite is a trigonal crystal system with a chemical composition of CaMg(CO3)2. It is mainly a mineral composed of calcium carbonate and magnesium carbonate (the ratio of CaCO3 to MgCO3 is approximately 1:1). It has complete cleavage and rhombohedral crystallization. . The colors are mostly white, gray, flesh-colored, colorless, green, brown, black, dark pink, etc., transparent to translucent, with glass luster, hardness 3.5-4, specific gravity 2.85-2.9. I remember when I went out to Hualien during my college days, I always couldn’t figure out how to distinguish between dolomite and marble on the beach. If you have a can of cold dilute hydrochloric acid nearby, you can do the trick. Massive dolomite is not prone to bubbles when exposed to cold dilute hydrochloric acid, while marble will immediately emit many tiny bubbles.
Dolomite can be used as the refractory inner layer of reformer furnaces used in steelmaking, slag-forming agents, cement raw materials, glass fluxes, kilns, fertilizers, construction and decorative stones, paints, pesticides and medicines, etc. It can be used in the fields of building materials, ceramics, glass and refractory materials, chemical industry, agriculture, environmental protection, energy saving and other fields.
Dolomite bricks are refractory products made of calcined dolomite sand. It usually contains more than 40% of calcium oxide (CaO), more than 35% of magnesium oxide (MgO), and also contains a small amount of silicon oxide (SiO2), aluminum oxide (Al2O3), ferric oxide (Fe2O3) and other impurities. The CaO/MgO ratio of natural dolomite fluctuates greatly. If the CaO/MgO ratio in the brick is less than 1.39, it is called a magnesia dolomite brick. According to the production process, dolomite bricks can be divided into: tar (asphalt) combined unburned bricks, light burned oil-immersed bricks and fired oil-immersed bricks. Dolomite bricks contain free CaO, which is prone to hydration and cracking in the air and is not suitable for long-term storage.
China's converter lining mainly uses tar-bonded dolomite bricks and tar-bonded magnesia dolomite bricks. Some factories use light-burned oil-impregnated and fired oil-impregnated magnesia dolomite bricks in vulnerable parts. Converters in countries such as Western Europe and Japan mainly use tar combined with heat-treated and fired oil-impregnated dolomite bricks and magnesia dolomite bricks. In addition, fired oil-impregnated magnesia dolomite bricks are also used as linings for some external refining furnaces.
Grinding and modification of ultrafine mica powder
With the development of industry, downstream application companies have increasingly higher requirements for the quality of mica powder. Currently, muscovite powder with a D90 of about 45 μm is mainly used in papermaking, latex paint, rubber and other industries, while high-end coatings, pearlescent mica and other products are The particle size of mica powder has put forward higher requirements, and the preparation of micro-nano-level ultra-fine mica powder is urgent.
During the grinding process, muscovite can still be tightly combined along the fresh surface after interlayer cleavage. It is one of the more difficult minerals to grind. Currently, micro-nano-level muscovite ultrafine powder is difficult to prepare using conventional grinding equipment. Many domestic mica manufacturers will mine high-quality muscovite and simply coarsely grind it for export. Others will be made into muscovite products with D90 particle size of about 45μm or even coarser, resulting in a waste of resources and reducing product competitiveness.
Mica ultrafine grinding preparation
At present, the ultra-fine grinding process of mica is divided into two grinding methods: dry method and wet method. Among them: the main equipment for dry ultra-fine grinding include high-speed mechanical impact mill, airflow mill, cyclone or cyclone flow autogenous grinding machine, etc. and the corresponding dry airflow classifier; the production equipment for wet grinding sericite powder includes sand mill, grinding machine, etc. Flaking machines and colloid mills are the main ones, while wet fine classification uses hydrocyclone classification technology.
The high-speed planetary roller mill can effectively perform dry and wet grinding of mica. The median diameter of the particles after grinding can reach 10 μm or less; the mica material stays in the grinding for a very short time, generally 5-10s. ; By adjusting the roller structure, mica powder with the required diameter-thickness ratio can be obtained. Under wet grinding conditions, mica powder can obtain a diameter-thickness ratio in the range of 20-60.
The stirring mill adopts special grinding media, which has good application effect in ultra-fine peeling of mica powder without damaging the surface of mica, and can make the diameter-thickness ratio of mica powder >60.
Mica powder surface coating or modification
The surface coating or modification of mica powder can prepare pearlescent mica and colored mica pigments to improve their corresponding properties in materials such as rubber and coatings. There are also many related studies.
Mica is surface-coated to prepare pearlescent mica and colored mica pigments. Currently, the liquid phase deposition method is mainly used. Common methods include alkali addition, thermal hydrolysis, buffering, etc. Commonly used coating agent titanium sources in industry are titanium tetrachloride and titanyl sulfate.
Application of mica powder
Mica powder can be used in fields such as electrical insulation materials, functional coating fillers, rubber fillers, plastic fillers, cosmetics and welding materials.
Using silicon nitride ceramics as raw material for mobile phone backplanes
As smartphone technology continues to develop and competition intensifies, mobile phone manufacturers have launched various new designs and innovations to attract more consumers, and ceramic backplanes are one of the tricks. Its emergence began in 2012 when Sharp launched a smartphone with a ceramic backplane. However, due to technical and cost issues, ceramic backplanes were only used in a few high-end brands at that time. However, with the development of processing technology, the application range of ceramic backplanes is becoming wider and wider.
In the field of ceramic backsheets, the protagonists are almost all zirconia ceramics, but recently researchers seem to have begun to think about silicon nitride. Compared with zirconia, silicon nitride is considered by researchers to be a superior and promising mobile phone backplane material, especially whisker-toughened silicon nitride ceramics. The reasons are as follows:
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(1) Silicon nitride ceramics have higher impact toughness, are not easily broken, are not easily damaged during machining, and have a higher yield;
(2) Silicon nitride ceramic has high thermal conductivity, which is more than 10 times that of zirconia ceramic, and it is easier to dissipate heat. Therefore, the heat generated when the mobile phone is running at high speed or the battery is charging and discharging is easy to dissipate, which is beneficial to the normal operation of the mobile phone. Avoid slowdowns and other phenomena;
(3) The dielectric loss of silicon nitride ceramics is two orders of magnitude lower than that of zirconia, making it more transparent to mobile phone signals and making it easier to communicate smoothly in environments with weak signals;
(4) Silicon nitride ceramic has higher hardness and lower density than zirconia, which can effectively reduce the quality of the fuselage, and its cost is close to that of zirconia;
(5) Silicon nitride ceramic is a colorless ceramic, which is relatively easy to color and has good coloring effect. It also has a jade-like texture and is suitable for use in, for example, mid-to-high-end mobile phone casings.
Therefore, the use of silicon nitride ceramic materials as communication device mobile phone backplane materials can, to a certain extent, make up for the shortcomings of current zirconia mobile phone backplane materials, and does have certain prospects.
Although there are not many reports on silicon nitride mobile phone backplane materials, it has been used as a structural ceramic for a long time and has fully proven its application stability and reliability in harsh environments such as automobile engines. If silicon nitride is used as a new mobile phone backplane material, it not only has the same excellent mechanical properties as zirconia, but also has the advantages of good texture, light weight, and more sensitive signals. It is a new mobile phone backplane material with great potential.
At present, the key to breakthrough lies in how to optimize the process to make Si3N4 ceramics not only easy to dissipate heat and rich in color, but also the preparation process can be simple and reliable, and the cost becomes acceptable. If the above difficulties can be overcome, perhaps one day in the future we will be able to see Si3N4 on smartphone backplanes and smart wearable devices.
7 Major Application Of Ultrafine Talc Powder
The nature of ultrafine talc powder is that it is a natural hydrated magnesium silicate mineral. It is inert to most chemical reagents and does not decompose when in contact with acids. It is a poor conductor of electricity, has low thermal conductivity and high thermal shock resistance. It can be heated when heated. It does not decompose even at high temperatures of 900°C. These excellent properties of talc make it a good filler. Today, we will sort out the application fields of ultrafine talc powder.
Application of talc powder in coating industry
Because talc has excellent physical and chemical properties such as lubricity, anti-adhesion, flow aid, fire resistance, acid resistance, insulation, high melting point, chemical inactivity, good covering power, softness, good gloss, and strong adsorption.
As a filler, the application of talc powder in coatings is mainly reflected in:
1. High whiteness, uniform particle size and strong dispersion;
2. Can serve as a skeleton;
3. Reduce manufacturing costs;
4. Improve the film hardness of the paint;
5. It can increase the stability of product shape;
6. Increase tensile strength, shear strength, bending strength, and pressure strength, and reduce deformation, elongation, and thermal expansion coefficient.
Application of talc powder in plastics industry
◆ Application in polypropylene resin
Talc is commonly used to fill polypropylene. Talc powder has the characteristics of lamellar structure, so talc powder with finer particle size can be used as a reinforcing filler for polypropylene.
◆ Application in polyethylene resin
Talc is natural magnesium silicate. Its unique micro-scale structure has certain water resistance and high chemical inertness, so it has good chemical resistance and sliding properties. Polyethylene filled with it can be used as engineering plastics. It has good chemical resistance and fluidity and can compete with ABS, nylon, and polycarbonate.
◆ Application in ABS resin
ABS resin is an amorphous polymer with excellent molding processability like polystyrene; it has good impact strength, low temperature resistance, high tensile strength and good creep resistance.
Application of talc powder in preparation industry
◆ Used as a dispersant for volatile oils
Talcum powder has a certain adsorption capacity, so it can adsorb volatile oil to the surface of its particles and disperse it evenly, increasing the contact area between volatile oil and liquid medicine, thereby increasing the solubility of volatile oil.
◆ Covered with powder coat layer
In sugar coating, talc powder can be used to coat the powder coating layer. White talc powder that passes through a 100-mesh sieve is suitable.
◆ Used as lubricant
Since talc has a layered structure that easily breaks into scales, it can be used as a lubricant to improve the compression moldability and fluidity of pharmaceutical powders.
◆ Used as filter aid
Talcum powder is not easy to react with drugs and has certain adsorption capacity, so it can be used as a filter aid.
Application of talc powder as pharmaceutical excipients
◆ Used as a disintegrant for hydrophobic drugs
Talcum powder is a hydrophilic substance. When added as an excipient to a drug, it can improve the hydrophilicity of the entire drug, making it easier for water to penetrate into the drug and making it easier to disintegrate.
◆ Used as anti-adhesive agent
Stickiness problem is a common problem in the coating process. It will lead to slow coating speed, longer production cycle, pellet sticking, reduced yield, film damage, affecting drug release and other problems.
◆ Increase the critical relative humidity of drugs
Application of talc powder in paper industry
The addition of talcum powder in the papermaking industry helps to increase filler retention and improve paper transparency, smoothness and printability, and makes the paper more ink absorbent.
Application of Talcum Powder in Cosmetics Industry
Talcum powder is a high-quality filler in the cosmetics industry. Due to its high silicon content, it can block infrared rays and enhance the sun protection and anti-infrared ray properties of cosmetics.
Application of talc powder in ceramic industry
In the ceramic industry, talcum powder plays an important role. The reason for the different colors of ceramics is that talcum powder is added to them. Different proportions and different ingredients can make ceramics display different colors, and at the same time, they can also make ceramics display different colors. After ceramic calcination, the density is uniform, the surface is smooth and the gloss is good.
Application of talc powder in textile industry
Ultra-finely ground talcum powder is often used as filler and bleaching agent in certain textiles, such as waterproof cloth, fireproof cloth, wheat flour bags, rope nylon, etc., which can enhance the density of the fabric and enhance heat and acid and alkali resistance. performance.
Application of ultrafine powder technology to develop edible resources
With the development of modern technology, the process has put forward higher and higher requirements for the particle size of powder. Many materials need to be crushed to the sub-micron level or nano-level, which cannot be achieved by traditional crushing technology and equipment. Ultrafine powder technology is developed based on this and involves the preparation and application of ultrafine powders and related new technologies. Its research content includes ultrafine powder preparation technology, classification technology, separation technology, and drying technology. , conveying mixing and homogenizing technology, surface modification technology, particle composite technology, detection and application technology, etc.
With the reduction of land, food will become a scarce commodity in the next century, and developing new food sources is a serious problem facing mankind. Ultra-fine powder technology can break cell walls, improve taste, and enhance digestion and absorption, thereby improving the bioavailability of edible resources and promoting the body's absorption of inedible parts of animals and plants. Therefore, it is widely used in the food industry. Been very widely used.
1 Grain processing
During the ultrafine milling process of flour, the glycosidic bonds may be broken and easily hydrolyzed by α-amylase, which is beneficial to fermentation. As the flour particles become smaller, their surface area becomes larger, which improves the adsorption, chemical activity, solubility and dispersibility of the material, thus causing changes in the macroscopic physical and chemical properties of flour. Wu Xuehui et al. proposed that flour with different particle sizes can be used to obtain flour with different protein contents to meet the needs of different products. The taste and absorption and utilization rate of the flour processed by ultra-fine powder are significantly improved. Wheat bran powder, soybean micron powder, etc. are added to flour to transform inferior flour into high-fiber or high-protein flour.
2 Deep processing of agricultural and sideline products
In recent years, plant-based green foods have become a focus of concern around the world, and edible plant-based foods are important resources for human survival. This situation can be improved by using ultra-fine powder technology. For example, the first step in the deep processing of edible plant stems and fruits is to control the crushing fineness to achieve different degrees of cell wall breaking and component separation.
3 Functional health food
Generally speaking, the high-tech means of ultrafine crushing are used to crush health food raw materials into ultrafine products with a particle size of less than 10 μm, which is called ultrafine health food. It has a large specific surface area and porosity, so it has strong adsorption and high activity. After ultra-fine processing of food, the nutrients in the food that are indispensable to the human body but difficult to eat can be fully absorbed by the human body, thereby maximizing the bioavailability and health care efficacy of the food.
4 Aquatic products processing
The ultrafine powder processed through ultrafine crushing of spirulina, kelp, pearls, turtles, shark cartilage, etc. has some unique advantages. The traditional method of processing pearl powder is ball milling for more than ten hours, and the particle size reaches several hundred meshes. However, if pearls are instantly crushed under low temperature of about -67°C and strict purification air flow conditions, ultrafine pearl powder with an average particle size of 1.0 μm and a D97 of less than 1.73 μm can be obtained. In addition, the entire production process is pollution-free. Compared with traditional pearl powder processing methods, the active ingredients of pearls are fully retained, and its calcium content is as high as 42%. It can be used as a medicinal diet or food additive to make calcium-supplementing nutritious foods.
Ultrafine powder technology is widely used in the food industry and plays a very important role in developing new edible resources and improving product quality.
The difference between quartz powder, silica powder, microsilica powder and white carbon black
Quartz powder and silica powder both refer to crystalline SiO2 powder. Simply put, they break stones into powder. Quartz powder is relatively coarse, while silica powder is relatively fine. Quartz powder is a powder obtained by crushing quartz raw ore through different processing equipment. Microsilica powder is an ultra-fine powder obtained by grinding quartz ore that has reached a certain purity, or a silica fine powder obtained by chemical means. However, their physical properties, chemical composition and application areas are different.
Microsilica fume is an industrial by-product, also called silica fume. Through the collection of smoke from smelting and incineration plants, fine dust containing high silica content is found.
Differences in properties between silica powder and quartz powder
1. Physical properties of silica powder and quartz powder
Microsilica powder and quartz powder are both fine powder materials, and their particle sizes are very small, usually less than 1 micron. However, their physical properties differ. Microsilica powder is usually light, loose, and low in density; quartz powder is relatively dense and high in density.
2. Chemical composition of silica powder and quartz powder
Microsilica and quartz powder are also chemically different. Silica powder is a type of silica (SiO2). Its crystal structure is similar to quartz, but due to its small size, it is usually an amorphous structure with many active groups on the surface. Quartz powder is made by crushing and finely grinding large crystal quartz minerals, and its chemical composition is SiO2.
3. Application fields of silica powder and quartz powder
Microsilica powder and quartz powder are widely used in industry, but their application fields are different. Microsilica powder is usually used in electronics, optics, ceramics, cosmetics, coatings, plastics and other fields. It is mainly used to increase the stability of materials, reduce material costs and improve the processing performance of materials. Quartz powder is mainly used in glass, ceramics, cement, building materials, metal surface spraying and other fields. Its high hardness and chemical stability make it an important component of many functional materials.
The effect of common minerals on plastic filling modification
Filling modification of plastics refers to a type of composite technology that adds low-cost fillers to resin to reduce the cost of polymer products. Its primary purpose is often to reduce costs. But since it is filling modification, it is also possible to improve certain properties after filling.
In thermoplastics, filling can improve the heat resistance, rigidity, hardness, dimensional stability, creep resistance, wear resistance, flame retardancy, smoke elimination and degradability of composite products, and reduce the molding shrinkage rate to improve Product accuracy; in thermosetting plastics, in addition to the aforementioned performance improvements, some resins are essential reinforcing materials in processing, such as unsaturated resins, phenolic resins and amino resins, which all need to be filled and reinforced.
Common modification properties of fillers
① Improve the rigidity of composite materials: specifically reflected in performance indicators such as flexural strength, flexural modulus, and hardness. The higher the silica content in the filler, the more obvious the rigidity modification effect will be. The order of rigidity modification of various fillers is silica (increase by 120%) > mica (increase by 100%) > wollastonite (increase by 80%) > barium sulfate (increase by 60%) > talc (increase by 50%) > Heavy calcium carbonate (increased by 30%) > light calcium carbonate (increased by 20%).
② Improve the dimensional stability of composite materials: specifically reflected in reducing shrinkage, reducing warpage, reducing linear expansion coefficient, reducing creep, and increasing isotropy. The order of dimensional stability effects is spherical fillers > granular fillers > flaky fillers >Fibrous filler.
③Improve the heat resistance of composite materials: The specific performance index is the heat deformation temperature. For example, the heat deformation temperature increases with the increase of talc powder content.
④ Improve the thermal stability of composite materials: Inorganic powders can absorb and promote analyte substances to varying degrees, thereby degrading the degree of thermal decomposition. In addition, inorganic fillers can also improve the wear resistance and hardness of composite materials.
Special modified properties of fillers
The reason why it is called the special modifying properties of fillers is that some fillers have and some do not have these modifying functions. The same filler may or may not have modifying functions under different conditions.
① Improve the tensile and impact properties of composite materials: Inorganic powder cannot always improve the tensile and impact properties of composite materials. It can only be improved when special conditions are met, and the improvement is not large. After the inorganic filler reaches a certain fineness, the tensile strength and impact strength of the composite material can be improved if the filler surface is well coated and a compatibilizer is added to the composite system.
② Improve the fluidity of composite materials: Most inorganic powders can improve the fluidity of composite materials, but talc powder reduces the fluidity of composite materials.
③ Improve the optical properties of composite materials: Inorganic powder can improve the covering, matting and astigmatism of composite materials. For example, titanium dioxide is a typical inorganic pigment with strong covering power.
④Improve the environmentally friendly combustion performance of composite materials: First, inorganic powder materials can make composite materials burn thoroughly, because cracks will occur during combustion and increase the oxygen contact area; second, inorganic powder materials can absorb some toxic gases when composite materials burn, Reduce toxic gas emissions; third, inorganic powder improves the thermal conductivity of composite materials, making combustion faster and shortening combustion time.
⑤ Promote the flame retardancy of composite materials: Not all inorganic powders are helpful for flame retardancy. Only inorganic powders containing silicon elements can help improve the flame retardancy and can be used as flame retardant synergists. The specific reason is that when silicon-containing materials are burned, a barrier layer can be formed on the surface of the combustion material to reduce the probability of oxygen contacting the material surface.
⑥ Optimize other properties of composite materials: nucleating agent function. When the particle size of talc powder is less than 1 μm, it can act as an inorganic nucleating agent in PP. To block infrared rays, inorganic powders containing silicon such as talc, kaolin, and mica all have good infrared and ultraviolet blocking properties.