The Chinese invented pottery as early as about 8000-2000 BC (Neolithic Age). Utensils made from clay are called pottery, and vessels made from porcelain are called porcelain. Ceramics is a general term for pottery and porcelain. Clay and porcelain clay, two different properties of earth, are used as raw materials, and they can be called ceramics through the process of batching, molding, drying, and baking.
With the development of modern science and technology, many new ceramic varieties have appeared in the past century. They no longer use or rarely use traditional ceramic raw materials such as clay, feldspar, quartz, etc., but use other unique raw materials, and even expand to the scope of non-silicate, non-oxide, and many new processes have appeared. So the meaning of ceramics goes far beyond the narrow traditional concepts of the past.
Initially, ceramics was the general term for pottery and porcelain. That is, a shaped sintered body obtained by molding and high-temperature sintering. Traditional ceramic materials mainly refer to aluminosilicates. In the beginning, people did not have high requirements for the choice of aluminosilicate, the purity was not significant, the particle size was not uniform, and the molding pressure was not high. The ceramic obtained at this time is called traditional ceramic. Later, it developed to high purity, small and uniform particle size, high molding pressure, and the sintered body obtained by sintering was called beautiful ceramics.
In the next stage, people researched the basis of the materials that make up ceramics, which significantly changed the concept of ceramics. The intrinsic mechanical properties of ceramics are related to the chemical bond structure of the elements constituting the ceramics. Chemical substances that can form a relatively stable three-dimensional network structure when crystals are formed can be used as ceramic materials. With the continuous development and progress of ceramic raw materials, the use of ceramic products has become more and more extensive. A new type of material has been formed—ceramic materials.
Ceramic materials refer to a class of inorganic non-metal materials made of natural or synthetic compounds through shaping and high-temperature sintering. It has the advantages of a high melting point, high hardness, high wear resistance, and oxidation resistance. It can be used as a structural material and a cutter material. Since ceramic also has some unique properties, it can also be used as a functional material. As ceramic materials become more and more refined, the language of scientists: we don't have to re-enter the ceramic age from the steel age.
Properties of ceramic materials
1. Mechanical properties of ceramic materials
Ceramic materials are the materials with the best stiffness and highest hardness among engineering materials, and their hardness is mostly above 1500HV. Ceramics have higher compressive strength, but lower tensile strength, and poor plasticity and toughness.
2. Thermal characteristics of ceramic materials
Ceramic materials generally have a high melting point (mostly above 2000 ° C), and have excellent chemical stability at high temperatures; the thermal conductivity of ceramics is lower than that of metal materials, and ceramics are also right thermal insulation materials. At the same time, the linear expansion coefficient of ceramics is lower than that of metals. When temperature changes, ceramics have excellent dimensional stability.
3. Electrical characteristics of ceramic materials
Most ceramics have good electrical insulation, so they are widely used to make insulation devices of various voltages (1kV ~ 110kV). Ferroelectric ceramics (barium titanate BaTiO3) have a high dielectric constant and can be used to make capacitors. Ferroelectric ceramics can change the shape and convert electrical energy into mechanical energy (with the characteristics of piezoelectric materials) under the action of an external electric field. It can be used as a loudspeaker, record player, ultrasonic instrument, sonar, medical spectrometer, etc. A few ceramics also have semiconductor characteristics and can be used as rectifiers.
4. Chemical properties of ceramic materials
Ceramic materials are not easily oxidized at high temperatures and have excellent corrosion resistance to acids, alkalis, and salts.
5. Optical properties of ceramic materials
Ceramic materials also have unique optical properties. They can be used as solid laser materials, visual fiber materials, optical storage, etc. Transparent ceramics can be used for high-pressure sodium lamps. Magnetic ceramics (such as ferrites: MgFe2O4, CuFe2O4, Fe3O4) have a wide range of applications in audiotapes, records, transformer cores, and large-scale computer memory components.
Classification of ceramic materials
Ceramic materials can be divided into ordinary materials and unique materials according to the different sintering raw materials. Everyday materials are sintered from natural raw materials such as feldspar, clay, and quartz. They are typical silicate materials. The main constituent elements are silicon, aluminum, and oxygen. These three elements account for 90% of the total crust elements. Ordinary ceramics Rich sources, low cost, mature technology. This type of ceramics can be divided into daily-use ceramics, building ceramics, electrical insulation ceramics, chemical ceramics, etc. according to their performance characteristics and uses. Specialized materials are made of high-purity artificially synthesized raw materials, which are formed by sintering with precise control technology, and generally, have specific unique properties to meet various needs. According to its main components, there are oxide ceramics, nitride ceramics, carbide ceramics, cermets, etc .; unique ceramics have select mechanical, optical, acoustic, electrical, magnetic, thermal, and other properties.
According to different uses, unique ceramic materials can be divided into structural ceramics, tool ceramics, and functional ceramics.
The main composition of alumina ceramics is Al2O3, which is generally higher than 45%. Alumina ceramics have various excellent properties. High-temperature resistance commonly can be used at 1600 ℃ for a long time, corrosion resistance, high strength, its strength is 2 ~ 3 times that of ordinary ceramics, and the higher one can reach 5 ~ 6 times. The disadvantage is that it is brittle and cannot accept sudden changes in ambient temperature. Extremely versatile, can be used as a crucible, engine spark plug, high-temperature refractory material, thermowell, seal ring, etc., can also be used as tools and molds.
The main composition of silicon nitride ceramics is Si3N4, which is a high temperature ceramic with high-temperature strength, high hardness, wear resistance, corrosion resistance, and self-lubrication. The linear expansion coefficient is the smallest among various ceramics, and the use temperature is as high as 1400 ° C. Has excellent corrosion resistance, in addition to hydrofluoric acid, can withstand the corrosion of various other acids, and can withstand the corrosion of different metals, and has excellent electrical insulation and radiation resistance. It can be used as high-temperature bearings; seal rings used in corrosive media, thermocouple sleeves, and metal cutting tools.
The main composition of silicon carbide ceramics is SiC, which is a high-strength, high-hardness, high-temperature-resistant ceramic that can maintain high bending strength when used at 1200 ° C to 1400 ° C. It is currently the most top temperature strength ceramic, silicon carbide ceramics. It also has excellent thermal conductivity, oxidation resistance, electrical conductivity, and high impact toughness. It is an excellent high-temperature structural material, which can be used for parts that work at high temperatures such as rocket tail nozzles, thermocouple sleeves, furnace tubes, etc.; its thermal conductivity can be used to make heat exchanger materials at high temperatures; and its high hardness and Wear-resistance for grinding wheels and abrasives.
Hexagonal boron nitride ceramics are mainly composed of BN, and the crystal structure is hexagonal crystal system. The structure and performance of hexagonal boron nitride are similar to graphite, so it is called "white graphite", its hardness is low, and it can be cut and has self-lubricity. It can be made into self-lubricating high-temperature bearings, glass forming molds, etc.
2. Tool ceramics
The main components of cemented carbide are carbides and binders. The carbides mainly include carbides, titanium carbides, tantalum carbides, niobium carbides, and vanadium carbides. The binders are mainly cobalt. Compared with tool steel, cemented carbide has higher hardness (up to 87 ~ 91HRA), good hot hardness (excellent abrasion resistance at about 1000 ℃). When used as a tool, the cutting speed is 4-7 times higher than that of high-speed steel, and the service life is increased by 5 ~ 8 times. Its disadvantages are that the hardness is too high, the brittleness is challenging to be machined. Therefore, it is often made into blades and inlaid on the tool holder. Cemented carbide is mainly used for machining tools; various molds, including drawing Extending die, drawing die, cold heading dies, mining tools, geology, and petroleum development, use a variety of drill bits, etc.
Diamond Natural diamond (diamond) is a precious ornament, while synthetic diamond is widely used in the industry. Diamond is the hardest material in nature and also has a very high elastic modulus. The thermal conductivity of diamond is the highest among known materials; Diamond has excellent insulation properties. Diamond can be used as drills, knives, abrasive tools, wire drawing dies, and dressing tools; diamond tools can be ultra-precision processed to achieve a mirror finish. However, diamond tools have poor thermal stability and significant affinity with iron group elements, so they cannot be used for processing iron and nickel-based alloys. They mainly process non-ferrous metals and non-metals and are widely used in ceramics, glass, stone, concrete, gemstones, Processing of agate, etc.
Cubic boron nitride (CBN) has a cubic crystal structure, its hardness is high, second only to diamond, and it has better thermal stability and chemical stability than diamond. It can be used for hardened steel, wear-resistant cast iron, thermal spray materials, and nickel. It is the cutting of metals. It can be made into tools, abrasive tools, wire drawing dies, etc.
Other tool ceramics include alumina, zirconia, silicon nitride, and other ceramics, but they are inferior to the above three tool ceramics in terms of overall performance and engineering applications.
3. Functional ceramics
Functional ceramics usually have unique physical properties and involve many fields. Typical ceramics with the same functions include dielectric ceramics, optical ceramics, magnetic ceramics, and semiconductor ceramics. Dielectric ceramics have the characteristics of insulation, hotspot, piezoelectricity, and strong dielectric properties. They are mainly used in integrated circuit substrates, thermistors, oscillators, capacitors, etc .; optical ceramics have fluorescent luminescence, high transparency, and point emission. Color effect and other characteristics, can be used in lasers, infrared windows, optical fibers, displays, etc .; magnetic ceramics are divided into soft magnetic, hard magnetic, magnetic tapes, various high-frequency magnetic cores are delicate magnetic ceramics, and electro-acoustic devices, instruments And the magnetic base of the control device is made of hard magnetic ceramics; semiconductor ceramics have the effect of resistance temperature change and thermionic emission, and are often used for temperature sensors and hot cathodes.
Beautiful ceramics are one of the unique values of new materials, and they have broad development prospects. Such beautiful ceramics with excellent properties may be widely used in place of steel and other metals in a wide range to achieve the purpose of saving energy, improving efficiency and reducing costs, the combination of beautiful ceramics and synthetic polymer materials. It can reduce the weight, size, and effectiveness of vehicles.
Excellent ceramic materials will become high-strength materials that can withstand high temperatures so that they can be used as various thermal engine materials, including aircraft engines, materials for fuel cell power generation, nuclear reactor wall materials, and pollution-free external combustion engine materials. Beautiful ceramics, high-performance molecular materials, new metal materials, and composite materials are listed as four new materials. Some scientists predict. With the advent of beautiful ceramics, humans will re-enter the ceramic age from the steel age.
Increasingly, beautiful ceramics are leading the new material world with excellent properties such as high-temperature resistance, super strength, and versatility. Decorative ceramics are high-performance ceramics that are made of pure, high-purity, synthetic inorganic compounds as raw materials and sintered by precise control processes. They are also known as advanced ceramics or new ceramics. There are many types of beautiful ceramics, which can be roughly divided into three categories-structural ceramics, electronic ceramics, and bioceramics.
This ceramic is mainly used to make structural parts. Some seals, bearings, cutters, ball valves, cylinder liners, etc. in the machinery industry are frequently subject to friction and are easily worn. Manufactured from metal and alloys can sometimes be damaged within a short time, and advanced structural ceramic parts Withstand this "tribulation."
2. Electronic ceramics
This refers to functional ceramics used to produce electronic components and structural components of electronic systems. In addition to their high mechanical properties such as high hardness, these ceramics can be "different" to changes in the surrounding environment, that is, they have excellent stability, which is an essential property for electronic components, and can withstand high temperatures.
Bioceramics is a ceramic material used to make the body's "skeletal-muscle" system to repair or replace human organs or tissues.
Graphite can be divided into natural graphite and artificial graphite. The two structures are similar, and their physical and chemical properties are identical, but their uses are quite different. In many studies, some researchers did not notice the difference between the two and generally referred to as graphite. This result of confusing the two has caused a lot of misleading, even the mistakes of decision-making, resulting in a significant waste of resources and economic losses. In this paper, from the perspective of the composition and properties of natural graphite and artificial graphite, we will talk about the characteristics and differences of the two, as well as their essential links and application directions.
1. Graphite classification and characteristics:
1.1 natural graphite
Natural graphite is formed by the transformation of carbon-rich organic matter under the long-term action of high temperature and high-pressure geological environment and is the crystallization of nature. The process characteristics of natural graphite depend mainly on its crystalline form. Minerals with different crystal forms have different industrial values and use. There are many types of natural graphite. According to various crystal forms, natural graphite is classified into three types: dense crystalline graphite, flake graphite, and cryptocrystalline graphite. China mainly has two kinds of scale graphite and cryptocrystalline graphite.
1.2 artificial graphite
Artificial graphite is similar to polycrystals in crystallography. There are many kinds of synthetic graphite, and the production process varies widely. All graphite materials obtained by carbonization of organic matter and high-temperature treatment by graphitization can be collectively referred to as artificial graphite, such as carbon (graphite) fiber, pyrolytic carbon (graphite), foamed graphite and the like. In the narrow sense, artificial graphite generally refers to carbonaceous raw materials (petroleum coke, pitch coke, etc.) with low impurity content as binder, coal tar pitch and the like as binders, after compounding, kneading, molding and carbonization (industrially called A bulk solid material obtained by a process such as calcination and graphitization, such as a graphite electrode or a hot isostatic graphite.
2. The difference and connection between natural graphite and artificial graphite
Given the above-mentioned natural graphite as raw material, which is usually narrowly defined artificial graphite, this paper only analyzes and discusses the difference and connection between natural graphite and fine artificial graphite.
2.1 crystal structure
Natural graphite: crystal development is relatively complete, the degree of graphitization of flake graphite is more than 98%, and the degree of graphitization of natural microcrystalline graphite is usually below 93%.
Artificial graphite: The degree of crystal development depends on the raw materials and heat treatment temperature. In general, the higher the heat treatment temperature, the higher the degree of graphitization. The artificial graphite produced in the industry currently has a degree of graphitization of usually less than 90%.
2.2 Organizational structure
Natural flake graphite: It is a single crystal with a simple structure and only crystallographic defects (such as point defects, dislocations, stacking faults, etc.), and macroscopically exhibits anisotropic characteristics. The crystallites of natural microcrystalline graphite are small, the crystal grains are arranged in disorder, and the pores after the impurities are removed are macroscopically isotropic.
Artificial graphite: can be regarded as a multi-phase material, including a graphite phase transformed by carbon particles such as petroleum coke or pitch coke, graphite phase transformed by coal tar binder coated around particles, particle accumulation or coal tar pitch A pore formed by heat treatment of the junction.
2.3 Physical form
Natural graphite: usually in the form of powder, can be used alone, but usually used in combination with other materials.
Artificial graphite: It has many forms, both powdery, fibrous, and massive. In the narrow sense, artificial graphite is usually in the form of a block, which needs to be processed into a particular shape when used.
2.4 physical and chemical properties
In terms of physical and chemical properties, natural graphite and artificial graphite have both commonalities and performance differences. For example, natural graphite and artificial graphite are good conductors of heat and electricity. However, for graphite powder of the same purity and particle size, natural flake graphite has the best heat transfer performance and electrical conductivity, followed by natural microcrystalline graphite, artificial graphite. Lowest. Graphite has excellent lubricity and certain plasticity. The crystal development of natural flake graphite is perfect, the friction coefficient is small, the lubricity is the best, the plasticity is the highest, and the dense crystalline graphite and cryptocrystalline graphite are the other, artificial graphite. Poor.
3. Application fields of natural graphite and artificial graphite
Graphite has many excellent properties and is widely used in industrial sectors such as metallurgy, machinery, electrical, chemical, textile, and defense. The application fields of natural graphite and artificial graphite have overlapping parts and different places.
3.1 Metallurgical Industry
In the metallurgical industry, natural flake graphite can be used to produce refractory materials such as magnesia carbon bricks and aluminum carbon bricks because of its excellent oxidation resistance. Artificial graphite can be used as a steelmaking electrode, and an electrode made of natural graphite is challenging to use in a more demanding steelmaking electric furnace.
3.2 Machinery Industry
In the mechanical industry, graphite materials are commonly used as wear and lubrication materials. Natural flake graphite has excellent lubricity and is often used as an additive for lubricating oils. For the equipment that transports corrosive media, piston rings, seals, and bearings made of artificial graphite is widely used, and no lubricating oil is needed for work. Natural graphite and polymer resin composites can also be used in the above fields, but the abrasion resistance is not as excellent as that of artificial graphite.
3.3 Chemical Industry
Artificial graphite has the characteristics of corrosion resistance, good thermal conductivity, and low permeability. It is widely used in the chemical industry to make heat exchangers, reaction tanks, absorption towers, filters, and other equipment. Natural graphite and polymer resin composites can also be used in the above fields, but thermal conductivity and corrosion resistance are inferior to artificial graphite.
With the continuous development of research technology, the application prospect of artificial graphite is immeasurable. At present, the development of artificial graphite products using natural graphite as a raw material is one of the critical ways to expand the application of natural graphite. Natural graphite has been used as an auxiliary raw material for some artificial graphite production. However, the development of artificial graphite products with natural graphite as the primary raw material is not enough research. It is the best way to achieve this goal by fully understanding and utilizing the structure and characteristics of natural graphite and using appropriate processes, routes, and methods to produce artificial graphite products with unique structures, properties, and uses.
When a plane is driving through the sky with a huge whistling sound, people standing on the ground always have to look up. At the same time as the heartfelt yearning and respect, people could not help but admire the rapid development of the aerospace industry in the motherland. Behind the successful development of each aircraft, the hard work of the vast number of scientific and technological workers is condensed.
The development of civil aviation ordinary passenger aircraft or military bombers, fighter planes and other models, on the one hand shows the achievements of China's aviation technology development, on the other hand also shows the confidence and determination of the R & D team to overcome difficulties, not afraid of challenges. As everyone knows, after the successful development of the aircraft, it is also very important to carry out technical maintenance and care of the aircraft. The emergence of technologies such as 3D printing has brought a new way for the maintenance of passenger aircraft and spacecraft.
Everyone knows that it takes a lot of manpower and resources to build a plane. It would be a pity if you stop using an aircraft just because some parts are damaged. 3D printing technology is used to manufacture replaceable old parts, and repairing parts with partial damage and deformation can help the full release of the overall performance of the aircraft, and the speed and safety of the aircraft can be effectively guaranteed. The advantages of 3D printing are also obvious compared to traditional maintenance techniques.
When manufacturing aircraft engines, seats and other components, the 3D printing cycle is short, materials are saved, and assembled products can be printed. It is worth noting that 3D printing can achieve better results in terms of component manufacturing accuracy and difficulty. Using 3D printing to create parts with complex shapes, various levels, and sharp edges, can better reflect the detailed design of the product and portray the texture.
Operators use 3D printing to repair certain special parts, and can flexibly change the size and shape of parts according to actual needs, so that the repaired parts have better ease of use. In general, 3D printing technology can be applied to repair metal parts of aero engines, such as blades, compressors, turbine engine components, and the like. When a component is partially worn or damaged, 3D printing technology can be used to extend the life of the 3D printed spacecraft component by removing the damaged material area and repairing the entire component using the reconstructed portion of the undamaged area.
The more common 3D printing repair process is directional energy deposition. How exactly the repair results of a component often depends on a number of factors, such as the level of component defect detection, the ability of the field operator to repair parts, the speed and cost of alternative repair techniques, and the restoration of components to their original shape with the same mechanical properties. Specific requirements. Imagine if it was a successful repair of a damaged component and then let it be put back into use. Isn't that a great pleasure?
The development of the aerospace industry will inevitably be accompanied by the emergence of high-end aerospace equipment and the continuous advancement of cutting-edge technology. Even if a spacecraft with advanced performance and first-class shape is developed, it cannot be meticulously maintained and care. Therefore, the use of 3D printing, artificial intelligence, intelligent manufacturing frontier technology to repair and maintain aircraft and other equipment will also become an important part of the aerospace industry forward.
Challenges and opportunities, impact and reshaping, removal and innovation, it is in the exploration and choice again and again, the original advantages and disadvantages of 3D printing can be revealed. In the aspects of production, maintenance and maintenance, the role that 3D printing can play is very huge, and its role depends to a certain extent on the degree of industry norm, the guidance of policy documents, and the level of professional talents. Wait.
The trekkers who are not afraid of the mountains and high roads, the mountains and rivers give back to the wonderful colors; the seas are not afraid of the wind and the waves, the sea returns a magnificent sunrise; the aerospace people who are not afraid of the journey, the sky gives away the wonderful space. It is the little effort and effort that has made China's aerospace industry a great success, and 3D printing, green manufacturing and other technologies will provide more energy for the future development of China's aerospace industry.
Ethylene bis ceramide is a beautiful white particle. Ethylene bisstearic acid amide emulsion industrial product melting point is 140~146.5 °C, density is 0.98g/cm3 (25 °C), non-toxic, insoluble in water, stable to acid, alkali and water medium, but powder in 80 It is wettable above °C. It is insoluble in most common solvents such as ethanol, acetone and carbon tetrachloride at room temperature. It is soluble in hot chlorinated hydrocarbons, and a particular chemical reaction prepares aromatic hydrocarbon solvents, but precipitates or gels when the solution cools, with a flashpoint of about 285 ° C. The ethylene bis-stearic acid amide emulsion by adding a high-quality ethylene bis-stearic acid amide dispersant. Ethylene bis-stearic acid amide emulsion has better adaptability than ethylene bis-stearic acid amide and is more widely used.
Ethylene bis ceramide emulsion is a new type of plastic lubricant developed in recent years. It is widely used in the molding of PVC products, ABS, high impact polystyrene, polyolefin, rubber, and plastic products. Lubricants such as paraffin, polyethylene wax, stearate, and other oils have not only excellent external lubrication but also have proper internal lubrication, which improves the fluidity of the melt-inserted plastic during plastic molding. The mold release property enhances the production of plastic processing, reduces energy consumption, and gives the product a high surface smoothness and smoothness. This product, because it contains two amide groups -C-NH- in its molecular structure so that the product is added to the plastic so that the plastic products have better antistatic properties so that the plastic products are not easy to absorb dust and dirt. This valuable and excellent property is especially important for household appliances and instrument housings and numerous engineering plastic products. As a lubricant, this product is used in combination with other oils and has a very significant synergistic effect. Improve the dispersibility of other ingredients such as colorants and fillers in plastics.
EBS emulsion is the abbreviation of ethylene bis ceramide emulsion. It is a high melting point of synthetic wax. The two-pole bond maintains a high degree of balance. Its inherent structure gives its unique compatibility and solubility. It can be used as the most thermosetting property. The thermoplastic internal lubricant and external lubricant are suitable pigment dispersants, which can make the operation smooth and improve the quality of the final product.
EBS emulsions are used as activators for various plastics and synthetic resins. Release agent. Pigment dispersant. Adhesion preventive agent. Lubricant. Surface gloss and activator for rubber products. Coating. Ink additives, etc. List as:
As a lubricant, EBS emulsion has excellent internal and external lubricity, mold release, and smoothness, can accelerate melting, reduce melt viscosity, save processing energy, increase product toughness, extend mold life, and give products a good appearance. Mainly used in PVC.PE.PP.PS.ABS resin, also used in phenolic and aminoplast.
EBS emulsion is a general-purpose plastic dispersant widely used in PVC products. ABS. High impact PS. The product can also be used in combination with other lubricants with a very significant synergistic effect and used as an anti-blocking agent and mold release agent in the rubber industry, as well as a hard rubber surface treatment agent.
EBS emulsion is a representative of the plastic lubricant stearic acid bisamide compounds and plays a pivotal role in the processing of thermoplastic resins such as rigid PVC, ABS, ABS, PC, and POM. The synthesis method of EBS can generally be divided into four routes:
1. Stearic acid is reacted with an amine compound;
2. The stearate is reacted with an amine compound;
3. stearoyl chloride is reacted with an amine compound;
4. Hydrolysis of nitrile compounds.
The most common ones are the first and the second. The first method is simple in process, the reaction conditions are not harsh, and there are no three wastes, but the purity is low; although the second method has a high purity of EBS, the energy consumption is large, the process is complicated, and the process is lengthy. At present, the most commonly used method in China is the first method. The latter three methods are widely used in foreign countries. The use of sophisticated process methods to obtain high-purity products is a new idea for the production of auxiliaries in advanced countries. It is worthy of reference from the domestic auxiliary industry. China has joined the WTO and should act in accordance with international thinking.
Use of EBS emulsion in plastic processing
Due to the presence of polar amide groups in the EBS molecule, EBS has process lubrication and a low-temperature anti-sticking effect on the polymer resin. EBS can be inserted into the interior of the polymer resin to reduce the interaction between the resin molecules and act as an internal lubricant. On the other hand, EBS can be rubbed against the metal surface by the mutual friction between the processing equipment in the resin melt. For external lubrication. Therefore, EBS mainly uses lubricating release agent in plastic processing to improve the quality of plastic products and improve the appearance of products. Secondly, it also plays the role of anti-sticking, smoothing, antistatic, improving pigment dispersion, and assisting stability.
Use of EBS emulsion in rubber processing
EBS can be used as rubber lubricant, anti-adhesive agent, mold release agent, filler surface modifier, and hard rubber surface treatment agent in rubber processing. Its outstanding performance is to improve the surface gloss of rubber sheets, hoses, and other products. It acts as a surface brightener.
Use of EBS emulsion in casting
When the spell is cast, EBS is added as a lubricant in the mixture of resin and sand to provide lubrication.
Use of EBS emulsion in metal processing
When drawing the wire, the use of EBS can increase the drawing speed, extend the life of the metal mold, and improve the smoothness of the surface of the fence. In addition, in powder metallurgy molding, prior to metal melting, bonding with EBS and using EBS as a lubricant for the metal mold can reduce the wear of the metal mold.
Use of EBS emulsion in paper coating
1% EBS improves the brightness of the paper coating. Because of the high melting point, it does not decompose during the heat sealing operation. This paper can be used for food packaging.
Use of EBS emulsion in the coatings industry
In the coatings industry, EBS can be used as a pigment grinding aid and dispersant. In addition, the addition of EBS to paints and paints can improve the saltwater resistance and water resistance, and enhance the smoothness of the baking surface.
EBS emulsion used as a defoamer
Used as the main active ingredient of amide defoamers in the pulp and paper process.
EBS emulsion synthetic fiber antistatic agent
33% of EBS can be used as an antistatic agent for synthetic fibers.
Other uses of EBS emulsion
EBS can be used as a melting point rising agent for petroleum products, and EBS is added to adhesives, waxes, etc., and has an anti-caking effect and an excellent mold release property. The addition of EBS to the asphalt increases the softening point of the road, lowers the viscosity, and improves the corrosion resistance to water or acid. The addition of EBS to the paint stripper improves the properties of the wax layer.
Flame retardants interfere with the combustion process during a fire, pyrolysis, or flame spread through chemical reactions or acting as a physical barrier. Adding flame retardants to wood can improve the fire resistance of the material without sacrificing the inherent advantages of wood materials. Although halogen and phosphorus organic flame retardants can effectively reduce HRR and enhance the fire resistance of wood, the environmental risks caused by toxic halogen products remain problematic. In contrast, inorganic flame retardants are greener and more suitable for sustainable applications. Most inorganic flame retardants have excellent gas barrier properties, including clay, clay nano-paper, silica, titanium dioxide, calcium carbonate, and magnesium-aluminum hydroxide. They reduce the HRR of wood by insulating the surface and delaying the thermal decomposition of the wood.
However, due to its isotropic adiabatic behavior, which produces a concentrated heat flux near the fire, traditional inorganic flame retardants generally have limited effectiveness in improving ignition performance.
The University of Maryland has proposed a scalable and straightforward method to form wood by combining densification with a nano-layered hexagonal boron nitride (h-BN) coating with a thickness of 30 µm. It densifies the wood, which increases the fire resistance of the wood. Densification has been proven to effectively enhance the flame retardant properties of wood, because it automatically forms a charcoal layer when exposed to flames, thereby providing adequate thermal insulation and oxygen barrier.
Besides, the 2D h-BN sheet can form a layered structure with anisotropic thermal properties, and exhibit excellent dimensional stability, ideal corrosion resistance, and oxidation resistance. It is attractive in terms of fire resistance and can not only reduce HRR, Can also enhance ignition performance. The thermal conductivity of h-BN in the plane and through-plane directions are 390 and 2 W / m / K, respectively. Thanks to the anisotropic thermal conductivity of h-BN, BN densified wood can effectively transfer the incoming heat along the surface of the timber and withstand vertical heat transfer. At the same time, the nano-layered h-BN coating can act as a physical barrier to oxygen and volatiles, thereby slowing the exothermic reaction.
Also, the coating method is simple and extensible, creating sandwich structures for BN dense wood longer than 25 cm and more comprehensive than 15 cm. Compared with other flame retardant wood materials, BN densified wood shows one of the most extended ignition delay times and the highest tensile strength. Flame retardant BN dense wood meets the requirements of large-scale production, high mechanical properties, and proper fire safety.
In this study, the author demonstrated a super durable and fire-resistant BN dense wood through a simple and effective coating method. The h-BN coating is uniform and stacked horizontally on the surface of 7 mm thick, dense timber, providing an excellent protective barrier against the diffusion of oxygen and the release of flammable volatiles when exposed to heat. Thanks to the anisotropic thermal conductivity of h-BN, BN densified wood shows excellent thermal diffusivity in the in-plane direction and effective thermal barrier in the in-plane direction. Compared to uncoated dense wood, the ignition temperature (Tig) of BN thick wood is increased by 41oC, the ignition delay time (tig) is doubled, and the maximum HRR is reduced by 25%, indicating an overall improved fire resistance. At the same time, BN densified wood also shows excellent mechanical properties, the high tensile strength of up to 471.5 MPa, and exceptional tensile strength of 362 Mpa · cm3 / g, demonstrating the super lightweight alternatives to these traditional structural materials.
This research shows that anisotropic thermally conductive h-BN flame retardant coating not only enhances the fire resistance of wood but also maintains the high strength of the material imparted by densification, representing a promising development of high-performance structural elements that can meet the direction of the requirements.