The difference between talcum powder and calcium carbonate as plastic filling

Generally, most of the plastic masterbatch is added calcium carbonate, but it must be calcite crystal ore. Both talcum powder and calcium carbonate can be added to plastics. In terms of cost, calcium carbonate is lower than talcum powder. In terms of production process, calcium carbonate is easier to process than talc powder. The polypropylene pellets used for strapping should be added with talcum powder and calcium carbonate, the ratio of which is: polypropylene: talcum powder: calcium carbonate = 70:25:5. For woven bags, calcium carbonate should be used, and the addition amount can reach more than 30%. Note the temperature during processing.

1. Both talcum powder and calcium carbonate are used for filling. The main purposes are:

• Increase dimensional stability (that is, reduce shrinkage)
• Increase the stiffness of the material,
• Increase the heat resistance of the material,
• Reduce material costs and other aspects.

But it also has its shortcomings:

• Density increases,
• If it is not used well, the impact toughness will decrease.
• The luster of the material has decreased.

2. Talcum powder has the same particle size distinction as calcium carbonate, generally 300 mesh, 600 mesh, 800 mesh, 1250 mesh and 2500 mesh. Of course, there are finer ones, and generally used in plastics, 800 mesh and 1250 can be selected. Target these two, so that the performance and price ratio can be the highest.
3. The price of talcum powder fluctuates. Generally speaking, it is not a big problem to set the price according to the number of meshes. For example, the general price of 800 mesh is between 700 and 850 yuan, and the price of 1250 mesh is between 1000 and 1000. Between 1280 yuan. The price is too high or too low is not normal.

About the difference between talcum powder and calcium carbonate:

• The shape of talcum powder is flake, so it has higher rigidity, dimensional stability and heat resistance temperature, and it has good reinforcement effect.
• Calcium carbonate is generally granular, so its stiffness and other aspects are not as good as talc, but its price is lower, and its whiteness is high, and it has little impact on plastic impact toughness.
• Talc has a nucleation effect on polypropylene, while calcium carbonate has no obvious effect in this respect.
• Calcium carbonate can generally be divided into light calcium carbonate and heavy calcium carbonate, but talc powder does not have this distinction, talc powder is ground from natural minerals.

Calcium carbonate/talc powder composite reinforced PP, its properties are as follows:

by ALPA Powder

Introduction of six advantages of jet mill

Since the advent of jet pulverization and classification equipment in the 1930s, various types have been continuously updated and the structure has been continuously improved, such as flat jet mills, circulating jet mills, impingement jet mills, jet mills, target jet mills and fluidized bed (jet) jet mills Wait.

Fluidized bed jet mill has the characteristics of low energy consumption, light wear, low pollution, low noise, fine particle size, uniform distribution, etc. It is widely used in synthetic resins, phenolic resins, polyvinyl chloride, pigments and dyes, powder coatings, colorants, and medicine , Cosmetics, advanced ceramics, magnetic powder, abrasives, metal powder, food, flavor, stearic acid, fat, wax, mineral powder, pesticide and wettable powder production.

The main advantages are as follows:

(1) The linear impact crushing and surface impact crushing of the traditional jet mill are transformed into three-dimensional impact crushing. The high-speed airflow generated by the jet impact is fully utilized in the material flow of the crushing chamber to generate gas-solid crushing and classified circulating flow in the crushing zone. Similar to the effect of fluidization, the efficiency of impact crushing and the comprehensive utilization of energy are improved. Compared with other traditional methods, energy consumption is reduced by 30%.

(2) The impact crushing zone and the gas-solid flow zone are placed in the middle space of the crushing chamber to avoid the impact erosion of the material driven by the high-speed airflow on the crushing chamber wall, and improve the most serious wear problem during the jet impact crushing process. Reduce the possibility of material contamination.

(3) Using high-purity nitrogen, argon and other protective gases as the working medium to prevent oxidation, the closed-loop operating gas consumption is small and the cost is low.

(4) In the process of fully closed loop operation, there is no dust flying, no pollution to the environment, and no harm to the human body.

(5) After jet mill pulverization, the activity of the powder is improved. The energy of the high-speed jet in the jet milling and classification process not only breaks the particles, but also changes the internal structure of the particles, especially the surface state to a certain extent. Gas flow can remove several atoms or ions from the particle lattice, resulting in mechanical loss of the crystal structure. In this way, with the ultrafine grinding of the powder material, the surface energy or internal energy of the particles increases, and the activity of the particles increases. The increase in particle activity is not only conducive to the progress of the chemical reaction, but also conducive to the adsorption and coating of the particles.

(6) The product has fine particle size, large output, suitable for large-scale production, high particle size classification accuracy, narrow product particle size distribution, and easy adjustment of product particle size.

by ALPA Powder

Advantages of jet mill in medicinal grinding

With the rapid economic development, higher requirements are put forward for the fineness and purity of various powders (including pharmaceutical powders) and their grinding equipment; ultra-fine grinding is very important for medicines and can affect its efficacy. And absorption in the body; the current market demand for micronized solid drugs is increasing year by year. At present, a jet mill is usually used for ultrafine grinding of drugs.

Micropowder crystallization is obtained by controlling the crystallization process conditions to obtain ultrafine particle crystals, which are then filtered, scrubbed, drained, and dried. Micropowder crystallization is obtained by ultrafine grinding of crystal particles. The defects of micro-powder crystallization are that it is difficult to filter, wash, drain, and dry, and it is easy to cause crystal leakage during the filtering and washing process, resulting in low yield and daily output, and the final product has low purity, many impurities, and adverse drug reactions. It is aggravated, so it is generally less used in production. At present, the ultra-fine grinding process is more widely used.

The airflow grinder accelerates the compressed air or inert gas through the nozzle, and uses the energy of high-speed elastic fluid (300~500m/s) or superheated steam (300~400℃) to make particles between particles, gas and particles, and particles With the wall and other parts, there are fierce impacts, shears, collisions, frictions and other effects. At the same time, under the effect of the centrifugal force of the airflow or the combined effect of the classifier, the coarse and fine particles are classified to achieve ultra-fine grinding. . The jet mill is a common preparation method for pharmaceutical powder, and is suitable for the grinding of antibiotics, enzymes, low melting point and other heat-sensitive drugs.

The advantages of jet mills in medicine are as follows:

• The range of particle size distribution is narrow, and the average particle size is fine;
• Good powder appearance and high product purity;
• Suitable for low melting point and heat sensitive drugs;
• Good airtightness and no pollution;
• Easy to operate;
• Grinding-mixing-drying on-line operation.

by ALPA Powder

Features and development direction of air classifier

Airflow classifier is a kind of equipment that uses centrifugal force of impeller rotation and drag force generated by airflow to classify materials. It is widely used in the classification and purification process of quartz, feldspar, mica, kaolin, and magnesium oxide. It has the characteristics of high classification accuracy, energy saving and high efficiency, and low production cost.

The air classifier includes a drive motor, a grading wheel, a fine powder outlet, a secondary air inlet, a raw material inlet, and a coarse powder outlet. Airflow classifier is a kind of airflow classification equipment. The classifier and cyclone separator, dust collector and induced draft fan form a set of classification system.

Under the action of the fan, the material moves to the classification area at high speed from the lower inlet of the classifier with the updraft; under the action of the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated; the fine particles that meet the particle size requirements pass through The gap between the grading wheel blades enters the cyclone separator or dust collector to collect; the coarse particles entrained by the part of the fine particles hit the wall and the speed disappears, descends along the cylinder wall to the secondary air outlet, and the strong elutriation of the secondary air separates the coarse and fine particles; The fine particles rise to the classification zone for secondary classification, and the coarse particles fall to the discharge port for discharge.

Performance characteristics of air classifier

It is suitable for the fine classification of dry micron products. It can classify spherical, flake and irregularly shaped particles, and can also classify particles of different densities. The particle size of the classified product can reach D97:3~150μm, the product particle size is steplessly adjustable, and the variety is extremely convenient to change.

The classification efficiency (extraction rate) is 60%~90%. The classification efficiency is related to the nature of the material and the particle content that meets the particle size. The fluidity of the material is good, and the particle content that meets the particle size requirement is high, the efficiency is high, and vice versa. The speed of the grading wheel is high, and the apex is cut accurately. Multi-stage classifiers can be used in series to produce products of multiple particle sizes at the same time.

It can be used in series with ball mills, vibration mills, Raymond mills and other grinding equipment to form a closed loop. The control system adopts program control, the running status is displayed in real time, and the operation is simple and convenient.

The system runs under negative pressure, and the dust emission exceeds 40mg/m³. After adopting the noise reduction measures, the equipment operation noise is not higher than 75dB (A).

Application field

Minerals, chemicals, metallurgy, abrasives, ceramics, refractories, medicines, pesticides, food, new materials, etc., especially suitable for the classification of non-mineral products such as calcium carbonate, kaolin, quartz, talc, and mica.

The development direction of air classifier

• Large-scale and refined

With the continuous expansion of the ultra-fine powder market and the expansion of production scale, the demand for large-scale ultra-fine crushing and fine classification equipment will continue to grow. The use of large-scale equipment can reduce the energy consumption per unit product, simplify the process, reduce the area occupied, and reduce the equipment investment and production cost of the unit product.

• Vortex air classifier gradually dominates the market

The vortex air classifier is simple in structure, adjustable in particle size, and has a wide range of adaptability. It is widely used in construction, mineral processing, fine chemicals, special ceramics and other industrial fields.

• Automatic control

Industrial control automation technology is developing towards intelligence, networking and integration. The automatic control of airflow classification can improve production efficiency, reduce labor intensity of workers, and improve the overall automation level of the powder processing industry and the core competitiveness of the enterprise.

by ALPA Powder

Grinding machine fault treatment and daily maintenance

The grinding of materials is an indispensable process in the production of products in many industries (such as metallurgy, mining, building materials, chemicals, ceramics, etc.). Due to the difference in the physical properties and structure of the materials, the selection of the grinder should also be analyzed in detail.

There are many grinding equipments on the market. Choosing a suitable grinding equipment can not only reduce the grinding time and reduce the waste of materials, but also help the wear of the grinding equipment.

Factors to be considered when selecting

• Material type and hardness

Material type and hardness is an important principle for choosing a grinder. The hardness of different materials is not the same. Usually Mohs hardness is used to indicate the hardness of the material. The Mohs hardness is divided into 10 levels. The greater the Mohs hardness number, the harder the ore and the more difficult it is to grind, and vice versa.

• Material moisture content

The water content of the material will also affect the choice of the grinder. When the water content is too large, the fine-grained material will agglomerate or stick to the coarse-grained material due to the increase in humidity, thereby increasing the viscosity of the material, reducing the discharge speed and increasing the productivity. Decline.

• The degree of dissolution of the ore

The degree of dissolution of the ore also directly affects the productivity of the grinder. When the ore is ground, it is easy to break along the cleavage surface. Therefore, the productivity of the grinder is correspondingly higher than that of the ore with a dense structure. .

• Incoming and discharging granularity

The granularity of incoming and outgoing materials is used to judge the type and level of grinding equipment required. If the content of coarse particles (large dry discharge port size) in the grinding material is high or the ratio of the largest ore supply to the width of the ore supply is large, the grinding ratio that the grinder needs to achieve (the particle size of the material before grinding is compared with that after grinding) The ratio of the particle size of the material) is large, so the productivity is reduced; when the content of fine particles of grinding material (close to or smaller than the size of the discharge port) is large or the ratio of the largest block of the ore to the width of the ore is small, the grinding ratio to be achieved is small , So its productivity is increased accordingly.

• Construction Site

The size of the construction site is also one of the factors that people consider when choosing a grinder. In addition, the location of the grinding equipment also affects the choice of the grinding machine.

• Yield

The output is also an important indicator that determines the selection of grinding equipment. The conventional understanding is that the higher the output requirement, the larger the specifications of the grinding equipment required, and the corresponding input and output will increase.

Common faults and treatment methods of grinding machines

• Worn spindle bearing

cause

1) Problems with bearing lubrication, heating or damage to the bearing, increase the transmission torque of the mating surface of the bearing inner ring and the shaft, produce relative movement, and cause the wear of the bearing position;

2) For long-term use, the metal material itself will produce normal metal fatigue, resulting in the generation of its fit clearance, which will cause the wear of the bearing position.

Fault judgment

1) Check the vibration of the pulley and observe the overall vibration and noise of the equipment when the equipment is running normally;

2) Use temperature measuring equipment to check the temperature of the bearing part;

3) Use testing equipment to check the vibration and relative displacement of the bearing part.

• The main shaft keyway, the wear of the key, the shaft and the pulley hole

cause

1) During long-term use, normal metal fatigue wear occurs on the mating surface of the pulley and the shaft, and the fit gap increases, causing the relative impact of the key and the keyway, leading to the wear of the keyway, and then increasing the wear of the shaft and the pulley hole.

2) The mating method of the key connection, the mating surface of the key and the keyway is the main transmission torque. In the actual operation process, the mating surface of the key and the keyway is most prone to metal fatigue wear, resulting in the operation process between the pulley shaft hole and the shaft Relative movement occurs, which in turn causes the wear of each mating surface in this part.

Fault judgment

1) Observe the swing degree of the pulley during the operation of the equipment;

2) Measure the temperature change of the mating surface of the pulley and the shaft;

3) Observe the overall noise and vibration during the normal operation of the equipment.

• Bearing heating damage

cause

1) During the installation process, the bearing clearance is too small or too large, which may cause heat, ablation, seizure, etc. during the operation of the bearing;

2) During normal operation, the bearing failed to add lubricating oil in time;

3) The service life of the bearing is too long, which leads to fatigue and wear of various parts of the bearing itself, and various index parameters cannot meet the requirements of normal use.

Fault judgment

1) Check the vibration of the pulley and observe the overall vibration and noise of the equipment when the equipment is running normally;

2) Use temperature measuring equipment to check the temperature of the bearing part;

3) Use testing equipment to check the vibration and relative displacement of the bearing part.

• Wear or fall off of the liner

cause

1) During use of the wear-resistant liner, it is normal for the liner to wear due to high-speed impact and erosion;

2) Damage to the fixing bolts of the liner may cause the liner to fall off.

Fault judgment

1) Loose or fall off of the liner will cause abnormal vibration and abnormal noise of the equipment;

2) The particle size increases.

• Increased overall equipment vibration

cause

1) Shaft wear, key editing, bearing damage, keyway damage, belt pulley shaft hole wear, liner looseness or fall off, and anchor bolt looseness will all cause the overall vibration of the equipment to increase. Check according to the specific conditions;

2) The rotor wears unevenly, and the dynamic balance fails.

Fault judgment

The overall vibration of the equipment has increased, and it is necessary to check all parts of the equipment as a whole to determine the source of the vibration.

• Belt tumbling

cause

1) The belt quality is not good;

2) Improper assembly.

Fault judgment

1) Choose a belt with qualified quality;

2) Install according to a reasonable method, and adjust the pulley on the same plane.

Maintenance of the grinder

As the core equipment for ore production, how to reduce the wear of the machine, extend the service life of the equipment, and convert economic benefits more efficiently in the daily use process, the following will share some methods of daily maintenance and maintenance of grinding.

• Check the machine regularly

1) When any grinding equipment is switched on and off, it should be paid attention to regularly shut down the machine and check the internal wear and tear of the machine.

2) During the inspection of the grinder, the machine must be completely stopped before the inspection can be carried out, so as to avoid a series of dangers. When overhauling the machine, be sure to check the wearing parts. The wearing parts must be replaced in time after they reach the maximum degree of wear resistance.

• Regularly check the condition of accessories

1) The conveyor belt is indispensable in the stone production line, and the driving of the machine is the contribution of the conveyor belt. Regularly adjust the tightness of the conveyor belt to ensure uniform force on the conveyor belt.

2) The bearing wears a lot in use. Frequent oiling can increase the service life of the bearing. Add 50-70% of the total amount in the bearing. The usual method is to pull the bearing and eccentric shaft out of the bearing cavity for processing.

• Do a good job of lubricating parts

1) Always pay attention to timely lubrication of the friction surface, which can ensure the normal operation of the machine and prolong the service life.

2) The grease used should be determined according to the conditions of use, temperature and other conditions. The grease added to the bearing seat is 50-70% of its volume, and must be replaced every three months; clean gasoline or kerosene must be used to clean the bearing and the dirt in the bearing seat when changing the oil.

Daily maintenance of grinder

Turn off the power switch, clean the materials scattered around the crusher, and check whether the screws are loose at the docking part of the motor and the reducer.

Lubricate the bearing parts regularly. The bearing parts are easily damaged parts. Only regular oiling can prolong the service life of the bearing.

by ALPA Powder

How to improve the use value of barite?

Barite is an important barium-containing mineral, with high specific gravity (4.3-4.7), low hardness (3-3.5), stable chemical properties, insoluble in water and acid, barite can be used as a white pigment (commonly known as Lith Powder), can also be used in the chemical industry, papermaking, textile fillers and other industrial sectors. In the glass production, it can act as a flux and increase the brightness of the glass, of which 80%-90% is used as a mud weighting agent in oil drilling.

The fineness of barite powder determines its use and value. Take oilfields as an example. Oilfields have strict requirements on the fineness of barite powder, which can neither be too coarse nor too fine. Improper fineness will cause changes in the rheological properties of the heavy mud itself, which will lead to serious Of drilling accidents occurred, so how to effectively control the fineness?

1.   The purpose of barite is to subdivide it according to the different fineness of barite after being crushed by a pulverizer. It is used as a mud weighting agent for drilling, with a fineness of more than 325 mesh. To prepare lithopone pigment, the fineness of barite powder is required to be at least 1250 mesh. Used as paint filler, barite powder requires more than 2000 mesh. The fineness of barite used in textiles is even finer.

2.  Selection of barite grinder

Which mill is used for 325 mesh barite powder, 1250 mesh barite powder and 2000 mesh barite powder?

The hierarchical impact mill can effectively control the fineness and output of barite, and the same equipment can crush different finenesses, and the fineness can be adjusted arbitrarily between 1-75 microns. Its characteristics are as follows:

1) Low energy consumption: It integrates centrifugal grinding, impact grinding, and extrusion grinding, which can save energy by 40-50% compared with other types of mechanical grinding machines.

2) High fineness: Equipped with self-diverting grading system, product fineness ≥2500 mesh.

3) Large feeding range: feeding particle size ≤50mm, the material only needs to pass through the first-level coarse crushing equipment.

4) Low wear: The crushing parts are made of new composite wear-resistant materials, with long service life, and no pollution when processing materials with Mohs hardness ≤5.

5) Strong mechanical stability: it can produce without stopping for 24 hours for a long time.

6) Full functions:

• It can grind needle-shaped materials to achieve the aspect ratio of the finished product to 15:1;
• There is no temperature rise during the grinding process, which is suitable for the grinding of heat-sensitive materials;
• The sintered agglomerated ultra-fine materials can be broken up, and the particle size recovery rate can reach 100%;
• With particle shaping function, it can effectively increase the bulk density.
• Materials that can grind fibrous tissue;
• It can grind materials with high moisture content and has a drying function;
•  

  It can grind strong viscous materials.

7) Negative pressure production, no dust pollution, excellent environment.

8) High degree of automation, strong stability and easy operation.

9) The entire system adopts automatic control, which can realize one-button start and stop, and the operation is simple and convenient. The connection with the central control can realize remote control.

Scope of application:

1.  Typical materials of non-metallic minerals include: hard kaolin, talc, graphite, calcite, gypsum, diatomaceous earth, wollastonite, barite, pyrophyllite, aluminum hydroxide and other materials ultrafine grinding and nano calcium carbonate, oxidation Superfine grinding and breaking up of cerium and other materials.

2.  Typical heat-sensitive materials include: lactose, wax, resin, fat, bone meal, plants, etc.

3.  The typical materials for ultra-fine processing of Chinese herbal medicines and raw materials are: pollen, hawthorn, shiitake mushrooms, pearl powder, stomach medicine, nimodipine, antibiotics, Ganoderma lucidum, gallnut, fleece-flower root, andrographis, mint, houttuynia, fern root, Pueraria lobata, Radix isatidis, etc.

by ALPA Powder

Technical indicators of calcium carbonate and its application in plastics

Some of the main technical indicators of calcium carbonate are: mesh number, whiteness, calcium carbonate content.

Mesh number: Mesh number refers to the number of holes in a certain area of ​​the screen. The larger the mesh number, the smaller the particle size, and the required production process will be more complicated. The larger the mesh, the stronger the activity of the filler particles, the easier it is to bond with the plastic matrix, the better the compatibility, but the worse the dispersibility. Common meshes are 400, 600, 800, 1000, 1200, 2000. Generally, fillers with large meshes need to be surface treated to improve their dispersibility.

Whiteness: Since pure calcium carbonate is white, the higher the purity of the calcium carbonate product, the whiter the product and the less variegated color. Ferrite, silicon, etc. will make the product appear yellow, dark and other variegated colors. Generally speaking, when the whiteness is higher than 90%, calcium carbonate can be used as a white dye for plastics, but many manufacturers are not satisfied with the 90% standard, and even launched products with a whiteness as high as 97%. Products with higher whiteness have higher grades, less impurities, and are not easy to damage processing equipment. When the plastic is colored, the color is purer and more stable.

Calcium carbonate content: refers to the calcium carbonate content of limestone raw materials, which can also be said to be purity.

Application of calcium carbonate in plastics

Calcium carbonate has a wide range of applications, and most plastics can be used. Adding calcium carbonate has a certain effect on improving certain properties of plastic products and expanding their application range. They can reduce resin shrinkage, improve rheological behavior, and control viscosity in plastic processing. It can also play the following roles:

• Improve the dimensional stability of plastic products

The addition of light calcium carbonate plays a skeletal role in plastic products, and has a great effect on the dimensional stability of plastic products.

• Improve the hardness and rigidity of plastic products

In plastics, especially soft polyvinyl chloride, the hardness gradually increases with the addition of calcium carbonate, and the elongation decreases with the increase in hardness. Light calcium carbonate with fine particles and high oil absorption has a large increase in hardness. Conversely, light calcium carbonate with a small particle coarse oil absorption value has a small increase in the hardness of the plastic. In soft PVC, the hardness growth rate of heavy calcium carbonate is the smallest, followed by light calcium carbonate (light calcium).

The plastic (resin) of light calcium carbonate generally does not have a reinforcing effect, and the particles of light calcium carbonate can often be infiltrated by the resin. Therefore, the normal effect of adding light calcium carbonate is to increase the rigidity of the resin, the elastic modulus and the hardness. Also increase. As the amount of addition increases, both tensile strength and extreme elongation decrease.

Different calcium carbonate, different addition amount, will have different hardness.

• Improve plastic processing performance

The addition of light calcium carbonate can change the rheological properties of plastics. Light calcium carbonate powder is often added in a relatively large amount, which will help it mix with other components and also help the processing and shaping of plastics. The addition of light calcium carbonate, especially after surface treatment of light calcium carbonate, can not only increase the hardness of the product, but also improve the surface gloss and surface smoothness of the product. The addition of light calcium carbonate can reduce the shrinkage, linear expansion coefficient, and creep properties of plastic products, creating conditions for processing and forming.

• Improve the heat resistance of plastic products

Adding light calcium carbonate to general plastic products can improve the heat resistance. For example, adding about 40% light calcium carbonate to polypropylene increases the heat resistance by about 200°C. When the filling ratio is less than or equal to 20%, the heat-resistant temperature increases by 8 to 130°C.

• Improve the astigmatism of plastics

In plastic products, some products require whitening and opacity, and some hope to extinction. The addition of light calcium carbonate can play a certain role in this regard.

Light calcium carbonate with whiteness above 90 has obvious whitening effect in plastic products. When combined with titanium dioxide and lithopone, the matting properties of plastic products have been greatly improved. In calcium plastic paper, low-density polyethylene and high-density polyethylene film, calcium carbonate can be added to achieve the effects of astigmatism and extinction, making it suitable for writing and printing. Calcium carbonate with better whiteness can also replace expensive white pigments.

• It can make the product have some special properties

The addition of light calcium carbonate to the cable material has a certain insulating effect, and the addition of light calcium carbonate can improve the electroplating performance and printing performance of some products. Fine or ultrafine light calcium carbonate is added to polyvinyl chloride (PVC), which has a certain flame retardant effect.

• Reduce the cost of plastic products

The price of ordinary light calcium carbonate and heavy calcium carbonate is far lower than the price of plastics. The addition of light calcium carbonate will reduce the cost of plastic products, so light calcium carbonate is called a filler or extender.

At this stage, adding calcium carbonate to reduce the cost of plastics is the main goal. With the improvement of the surface properties of calcium carbonate and the controllable shape and particle size, calcium carbonate will gradually become a functional filler for the purpose of strengthening or imparting functionality.

Filling the plastic with calcium carbonate is like adding a skeleton to the plastic, which improves the dimensional stability and hardness of the plastic, and can also improve the wear resistance and gloss of the plastic to a certain extent. As usual, it is used for PP, PE, PVC sheets and pipes.

Calcium carbonate is non-toxic, tasteless, and environmentally free. It is a common mineral in the natural environment. It is suitable to be added to biodegradable plastics and food packaging plastics without adversely affecting people and the environment. Studies have also shown that biodegradable plastics added with calcium carbonate degrade faster in the soil.

Light calcium carbonate has a characteristic. It is relatively oil-absorbing and easy to absorb plasticizers in plastics, resulting in poor plasticizing effect. To improve this situation, calcium carbonate can be modified.

by ALPA Powder

Application of graphene after airflow classification in many fields

Graphene is a hot product nowadays. Graphene is a revolutionary material, and its application continues to expand with the deepening of related research. The good properties of graphene also determine that it has an extraordinary market value.

1.   The characteristics of graphene

Graphene has good strength, flexibility, electrical conductivity, thermal conductivity and other properties. It is the material with the highest thermal conductivity so far and has very good thermal conductivity, so it is widely used in the new heating industry.

Like the conventional heating film, graphene needs to be energized to generate heat. When the electrodes at both ends of the graphene heating film are energized, the carbon molecules in the heating film generate phonons, ions and electrons in the resistance, and the generated carbon molecular groups interact with each other. Friction and collision (also known as Brownian motion) generate heat energy, and the heat energy is radiated uniformly in a planar manner by controlling the far infrared rays.

After the graphene is energized, the total conversion rate of effective electrothermal energy is more than 99%, and the special superconductivity is added to ensure the stability of the heating performance. However, it is different from the conventional metal wire heating film in that the heating is stable and safe, and the emitted infrared rays are called "light of life".

2.  What aspects of graphene is used after being classified by the airflow classifier

• Flexible graphene transistor

The graphene transistor is a single-electron nanodevice. This kind of transistor has received great attention from the market since its research and development. At present, some flexible graphene transistors have been applied. The main advantage of graphene transistors is that they are easy to operate at room temperature, while having the characteristics of low voltage and high sensitivity. These characteristics make graphene transistors superior to silicon transistors, and at the same time promote the development of microchip technology. In addition, due to the inherent characteristics of graphene, this transistor has extremely high flexibility and foldability.

• Graphene sensor

A sensor is a device that senses changes in the surrounding environment (such as heat, motion, light, pressure, humidity, etc.) and provides feedback through output signals (usually light, mechanical or electrical signals). Because graphene has a large surface-to-volume ratio, unique optical properties, excellent electrical conductivity, high carrier mobility and density, and high thermal conductivity, graphene can be used as a sensor in different fields, including biosensors , Diagnostic technology, field effect transistors, DNA sensors and gas sensors.

• Graphene for lithium batteries

With the wide application of lithium batteries, the types of lithium batteries are constantly enriched. Lithium-ion batteries are considered to be one of the promising electrochemical energy storage systems, with strong application potential in the fields of civil, national defense, and aerospace. However, at this stage, lithium batteries still have certain limitations. Graphene can be integrated into the positive and negative electrodes of different battery frames to enhance battery performance and increase the charge-discharge cycle rate.

• Graphene transparent conductor

Transparent conductors are the core part of devices that require high surface resistance and high transparency, such as touch screens, light-emitting diodes, and solar cells. When used as an electrode, the device must meet the conditions of light input/output. Traditional transparent conductors are composed of highly doped semiconductor oxides, and composite materials composed of graphene, silicon, metal and carbon nanotubes can be used as transparent conductor films. Among them, the transparency of graphene-silicon film is as high as 94%, and the conductivity is 0.45S/cm. This type of composite material has excellent overall performance as a transparent conductor.

• Graphene structure composite material

Graphene and different materials form composite materials, which are used in various applications, such as aviation. Studies have shown that adding graphene to the material can greatly improve the performance of the material. For the aviation industry, a lightweight composite material can save fuel costs. Graphene-based composite materials have great potential and can be used as an important choice for the development of new materials.

• Graphene catalyst carrier

Graphene and its derivatives have rich surface properties, sheet-like morphology, high surface area and high electron mobility. Studies have proved that it is a very effective catalytic material. Graphene is a chemically inert substance. Adding functional groups can change the characteristics of graphene and is suitable as a catalytic carrier.

After being classified by the air classifier, accurate and efficient powder can be obtained, and the particle size is concentrated, so that the high-precision graphene powder can be widely used in many fields.

by ALPA Powder

What is the impact of the large water content of the raw material on the pulverization process of the jet mill

Jet mills are favored by many industries. Jet mills can pulverize raw materials into powder, which can increase its added value to a large extent. The jet mill is not suitable for all materials. When the equipment crushes the materials, the nature of the feed is very strict. One of the feeding properties is the moisture content. The moisture content will change under the influence of weather. One is too large and the other is too small. These two conditions have different effects on production. The following analysis is carried out for these two situations:

1. Low moisture content

The jet mill is relatively easy to crush materials with low water content. Due to the low moisture content, material blockage is not easy to occur during production, and the production process is relatively smooth. Therefore, the efficiency of the jet mill is relatively high in this case, and it is also the best state of the jet mill.

2. Large moisture content

When the moisture content is large, the jet mill is prone to sticking and blocking during the crushing process, which makes the crushing process abnormal. The pulverized powder is easy to stick around the grinding roller, grinding ring and liner. At this time, it will reduce the performance of the parts and reduce the production efficiency, and this situation will also cause the phenomenon of increased wear. In addition, when the moisture content is large, if the air volume of the blower in the mill is small, the animal material cannot be blown to make it float; if the air volume of the blower is increased, the unground materials may float together, and these unqualified powders will stick. On the analysis machine, when the circulating air flows to the air duct, the material will block the air duct, the grinding cavity cannot get good ventilation and heat dissipation, and the internal temperature rises, which reduces the working efficiency of the motor, which is very unfavorable for the production of the mill.

From the above situation, it can be concluded that a small moisture content is beneficial to the production of the mill, while a large moisture content will cause a decrease in the efficiency of the jet mill and an increase in wear. Therefore, in actual production, it is necessary to add The water content of the materials in the mill must be strictly controlled.

by ALPA Powder

The deep processing technology of kaolin

Kaolin is a clay mineral with kaolinite as the main component, commonly known as "china clay", including: kaolinite, perlite, dickite, and halloysite. The crystalline chemical formula of kaolinite is AI₄[Si₄O₁₀](OH)₈ , which is a layered silicate mineral of 1:1 type. It consists of a silicon-oxygen tetrahedral layer and an aluminum-oxygen octahedral layer. The layers are composed of hydrogen-oxygen bonds. connect.

According to its texture and plasticity, it can be divided into hard kaolin, soft kaolin, and sandy kaolin. According to its genesis, it can be divided into coal series kaolin and non-coal series kaolin.

The gangue minerals of kaolin include feldspar, quartz, titanium oxide minerals, iron minerals, and mica. The main chemical components are silicon dioxide, aluminum oxide, iron oxide, calcium oxide and magnesium oxide, organic mixtures, and loss on ignition. , Alkali metal oxides, fluid anhydride.

The firing color of kaolin is white or close to white, and the maximum whiteness is greater than 95%; the hardness of soft kaolin is 1~2, and the hardness of hard kaolin can reach 3~4; it has good molding, drying and sintering properties; easy to disperse in water , Suspended, into a stable suspension; has excellent electrical insulation properties, the resistivity is greater than 1010Ω·cm-1 at 200°C. It has good resistance to acid solubility, the cation exchange capacity (CMC) is generally 0.03-0.05mmol/g, and it has good fire resistance, with a refractoriness of 1750-1790°C.

Kaolin has good properties such as plasticity, dispersibility, fire resistance, cohesiveness and stability, and has been widely used in many fields such as agriculture, refractory materials, papermaking, ceramics, and rubber.

With the emergence and development of modification technology and nanotechnology, modified kaolin and nano kaolin have shown more excellent performance, which greatly expands and extends the application field of kaolin. About 45% of global kaolin is used in papermaking, about 16% is used in refractory materials, about 15% is used in ceramics, and glass fiber and cement preparation fields each account for about 6%.

The deep processing technology of kaolin

The kaolin product after beneficiation and purification reaches the best quality in the natural state, but still does not meet the requirements of some applications, so further processing of kaolin is required. The deep processing of kaolin includes: calcination, superfine grinding, surface modification .

• Superfine grinding

In the process of ultrafine pulverization of kaolin, the product layer fractures to produce flaky particles. Therefore, the ultrafine grinding of kaolin is also called peeling. The stripping machines used in industry are mainly high-pressure homogenizers, mixing mills, etc.

The high-pressure homogenizer uses the shearing force generated by the mutual friction generated when the slurry is sprayed under high pressure and the crushing effect generated by the sudden pressure drop after the spraying, which destroys the kaolinite crystal structure and causes the hydrogen bond between the crystal layers. Fracture, causing the kaolin layers to burst and peel off one by one.

When pulverizing kaolin ultrafinely with a stirring mill, ceramic balls, glass balls, iron stone, and corundum are used as the pulverizing medium in order to avoid secondary pollution and ensure the whiteness of the product. Since the filling rate of the crushing medium will affect the production capacity of the mill, there are many media and the peeling effect is good, but the processing capacity is low, so the optimal filling rate should be determined through experiments based on the equipment performance.

• Calcination processing

The calcination of kaolin can eliminate the structural water in kaolinite minerals, and at the same time can remove organic pollution sources and some volatile substances. It is currently one of the most effective methods for processing kaolin. It can not only improve the purity and whiteness of kaolin, but also change the properties of kaolin, so that kaolin has properties that it did not have before calcination, such as: low density, large specific surface area, good covering properties, and good wear resistance. The satin firing process and equipment of kaolin mainly include inverted flame kiln calcination, rotary kiln calcination, vortex air flow calcination, and tunnel kiln calcination.

When kaolin is used as ceramics, an inverted flame kiln is usually used for calcination. Before the kaolin enters the kiln, the moisture content of the kaolin is controlled at about 15%, so that the kaolin will not cement during the calcination process and save fuel.

At present, most of the rotary kilns used are horizontal rotary kilns. The rotary kiln uses low-heat coal as the fuel. The rotation of the rotary kiln makes the kaolin continuously tumble, and the direction of movement is opposite to the direction of the high-temperature airflow, so that the kaolin and the high-temperature flue gas are thoroughly combined. Heat exchange, continuous production is possible.

The vortex air calcination uses a conical vortex to process the selected kaolin powder. During the calcination process, a rotating upward hot air flow is formed by a vortexer, and extremely fine materials are dispersed into a cone inner reaction chamber for calcination through a sprayer. At this time, the amorphous calcined kaolin obtained can be further heated, which will cause new The crystalline and physical state of the material is higher than the calcined kaolin in the first stage, and it has better characteristics.

The products calcined in the tunnel kiln have become sintered refractory clinker. In this process, the kaolin is made into a specific shape and sent to the tunnel kiln for calcination. The sintered material is crushed, classified, and made into a standard particle size. Enter the ball mill to grind to -120 mesh and -200 mesh or send to sieve to separate out 80-120 mesh.

by ALPA Powder