Overview of the application fields of nano-silica

Silica is one of the extremely important new inorganic materials, especially nano-scale silica due to its small particle size, many micropores, large specific surface area, strong surface adsorption, large surface energy, high chemical purity, and good dispersion. Good performance, thermal resistance, electrical resistance and other aspects have specific properties, with its superior stability, reinforcement, thickening and thixotropy, it is widely used in many disciplines and fields.

1. Application in rubber industry

Rubber is an elastomer with excellent stretchability, but its overall performance is not satisfactory. In the process of producing rubber products, it is usually necessary to add carbon black to the rubber compound to improve strength, wear resistance and aging resistance, but due to carbon The addition of black makes the products all black, and the grade is not high. The advent of silica in my country has laid a material foundation for the production of a new generation of rubber products with novel colors and excellent performance. After adding a small amount of silicon dioxide to ordinary rubber, the strength, wear resistance and aging resistance of the product can reach or exceed that of high-grade rubber products, and the color can be kept unchanged for a long time.

In the rubber industry, silica is usually used in vulcanized silicone rubber, medical rubber products, tires, hoses, tapes and daily necessities (rubber shoes, electrical appliances and stationery).

2, The application in the plastic industry

In thermoplastics, fumed silica can improve the toughness of the plastic. After it is added to the plastic, it can improve the toughness of the material without weakening the rigidity of the material, and even increase the rigidity of the material. In thermosetting plastics, adding fumed silica to epoxy resin can significantly improve its brittleness, overcome the defects of material rigidity and strength reduction caused by elastomer toughening, and achieve the purpose of strengthening and toughening. In plastics, silica can also be used as a flame retardant. Because fumed silica improves the strength of the carbon-silicon layer through the physical process in the condensed phase, it can prevent the transfer of heat and substances during combustion.

3. Application in coatings

In light-curing coatings, nano-silica is filled into UV-curing coatings, so that the hardness of the coatings after curing is significantly improved, and the heat resistance is also improved. At the same time, it can improve the curing speed, coating hardness, adhesion and thermal stability at low temperature of the UV-curable coating film.

In architectural coatings, silica can effectively reduce the color difference of coatings caused by ultraviolet and infrared light, and improve the aging resistance of exterior wall coatings. It can also significantly enhance the hardness, adhesion and weather resistance of the coating, improve the viscosity and anti-settling ability of the coating, and enhance the stability of the coating.

In the coating of inkjet printing paper, if nano-silica is added to the pigment, a special coating for digital color inkjet printing paper with good performance can be made, which can not only make the loading of the coating moderate, but also effectively solve the problem of formaldehyde. The printing effect is good, the material is easy to get, it can be said to be economical and practical. In addition, adding silica to plastic and metal coatings can significantly improve the performance of the material.

4, The application in the field of ceramics First, silicon dioxide is the main component of quartz ceramics.

Secondly, as an additive, it can also effectively enhance the performance of ceramics. For example, adding silicon dioxide instead of nano-Al2O3 to 95 ceramics can not only play the role of nanoparticles, but also the second phase particles, which not only improves the strength and toughness of ceramic materials, but also improves the hardness and hardness of ceramic materials. Elastic modulus and other properties, the effect is more ideal than adding Al2O3. The use of silicon dioxide to compound the ceramic substrate not only improves the compactness, toughness and smoothness of the substrate, but also greatly reduces the sintering temperature. In addition, the application effect of silica in ceramic products such as ceramic filters and corundum balls is also very significant.

5. Application in the field of drug carrier and catalysis

Nano-silica is physiologically inert and highly adsorbable, and is often used as a carrier in the preparation of fungicides. When nano-silica is used as a carrier, it can absorb antibacterial ions to achieve the purpose of antibacterial. It can be used in the manufacture of refrigerator casings, computer keyboards, etc. Nano-silica has large specific surface area, high porosity, and many surface active centers, so it has potential application value in catalysts and catalyst supports. Using nano silicon dioxide as the basic raw material, the composite oxide containing nano silicon dioxide can be prepared by using sol-gel technology. When the composite oxide is used as a catalyst carrier, it will show unique reaction performance for many structure-sensitive reactions. The catalytic activity of the reaction is high, the selectivity is good, and the catalytic activity can be maintained for a long time during the reaction.

6. Application in electronic packaging

The three main materials of electronic packaging are substrate material, molding compound, lead frame and solder. Among the molding compounds, epoxy molding compound (EMC) is the mainstream of integrated circuit packaging at home and abroad. In EMC, the content of silica powder accounts for 60% to 90%. In electronic packaging, it is mainly required that integrated circuits have high moisture resistance, low stress, low α-rays, dip soldering and reflow soldering resistance, and good plastic packaging process performance. In response to these requirements, the epoxy molding compound must be doped with inorganic fillers in the resin matrix. The currently used inorganic fillers are basically silicon micropowder, which can reduce the thermal expansion coefficient of the molding compound, increase thermal conductivity, reduce the dielectric constant, and be environmentally friendly. , Flame retardant, reduce internal stress, prevent moisture absorption, increase the strength of plastic packaging materials, reduce the cost of packaging materials, etc.

7. Application in sealants and adhesives

Sealants and adhesives are important products with large volume, wide range and wide application range. It requires product viscosity, fluidity, and curing speed to reach the best conditions. Our country’s products in this field are relatively backward, and high-grade sealants and adhesives are all dependent on imports. Foreign products in this field have used nano-materials as modifiers, and silica is the preferred material. It mainly coats a layer of organic materials on the surface of silica to make it hydrophobic. Add it to the sealant A silica structure is quickly formed in the medium, that is, small silica particles form a network structure to inhibit colloidal flow, accelerate the curing speed, and improve the bonding effect. Due to the small size of silica particles, the sealing and impermeability of the product are also increased. .

8. Application in FRP products

Although FRP products have the advantages of light weight, high strength, and corrosion resistance, they have low hardness and poor wear resistance. Relevant experts added silicon dioxide to the gel coat resin by ultrasonic dispersion method, and conducted a performance comparison experiment with the gel coat without adding silicon dioxide, and found that its Mohs hardness increased from the original 2.2 (equivalent to the hardness of gypsum) to Grade 2.8~2.9 (grade 3 is the hardness of natural marble), the wear resistance is increased by 1~2 times, due to the grafting and bonding of nanoparticles and organic polymers, the toughness of the material is increased, so the tensile strength and impact strength Increased by more than 1 times, the heat resistance is also greatly improved.

9. Application in cosmetics

In the past, organic compounds were mostly used as ultraviolet absorbers in sunscreen products, but there were problems such as increasing the amount of addition in order to protect the skin from ultraviolet rays as much as possible, which would increase the occurrence of skin cancer and chemical allergies, while silicon dioxide is an inorganic Composition, easy to be compatible with other components of cosmetics, non-toxic, tasteless, does not have the above-mentioned problems, and itself is white, can be easily colored, especially valuable is that silica has strong ultraviolet reflection ability and good stability, and is irradiated by ultraviolet rays. It will not decompose in the end, will not change color, and will not chemically react with other components in the formula. These outstanding characteristics of silica have laid a good foundation for the upgrading of sunscreen cosmetics.

10, the application in the field of optics

High-pressure sodium lamps and various iodine arc lamps used for photography and photography require strong lighting, but after the filament is heated, 69% of the energy is converted into infrared rays, which shows that a considerable amount of electrical energy is converted into heat energy and consumed. Part of it is converted into light energy for lighting. At the same time, the heating of the lamp tube will also affect the life of the lamp. How to improve the luminous efficiency and increase the illuminance has always been a key problem to be solved urgently. Since the 1980s, scientific research and technical personnel have made a multi-layer interference film with silicon dioxide and nano-titanium dioxide particles, with a total thickness of micron, lining the inner wall of the bulb cover. The result is not only good light transmittance, but also strong infrared reflection. ability. According to experts’ estimates, under the same light brightness, this kind of lamp can save 15% of electric energy compared with traditional halogen lamps.

11. Application in textile field

With the development of science and technology and the improvement of human living standards, people have put forward the requirements of comfort, novelty and health care for clothing, and various functional textiles have emerged as the times require. Here, nano-silica plays a huge role. At present, people have applied it to anti-ultraviolet, far red antibacterial and deodorizing, anti-aging and so on. Another important feature of the fibers added by nanomaterials is that they have a strong absorption of infrared rays from the human body, which can increase the warmth retention effect and reduce the weight of clothes. Clothes made of fibers added with infrared absorbing nanomaterial powder can weigh about Reduced by about 30%.

12. Applications in the field of agriculture and food

In recent years, developed countries have developed some new application fields of nano-silica. For example, in agriculture, the use of nano-silica as an agricultural seed treatment agent can increase the yield of vegetables (cabbage, tomato, yellow, cotton, corn, wheat, etc.) and mature in advance. For example, nano-silica can be used in herbicides and insecticides. If a small amount of nano-silica is added to the formulation of granular insecticidal thorns, it will effectively control and prevent harmful substances. In the food industry, nano-silica also has many applications, such as food packaging bags added with nano-silica, which can keep fruits and vegetables fresh; the application of nano-silica in wine production can purify and prolong the freshness period It can also be used as a high-efficiency fungicide for the prevention and treatment of various diseases of fruits and vegetables.

13, the application in the field of lubrication

Silica can also be used as a lubricant and is an excellent flow promoter, mainly used as a lubricant, anti-sticking agent, and flow aid. It is especially suitable for the granulation of oils and extracts, and the granules produced have good fluidity and compressibility. It can also be used as a glidant in direct compression. As a disintegrant, it can greatly improve the fluidity of granules, increase the bulk density, increase the hardness of the prepared tablet, shorten the disintegration time limit, and increase the drug dissolution rate. In the manufacture of granules, it can be used as an internal desiccant to enhance the stability of the drug. It can also be used as a filter aid, clarifier, defoamer, and suspending agent and thickener for liquid preparations.

14. Application in papermaking

In the paper industry, fumed silica products can be used as paper sizing agent, which can improve the whiteness and opacity of paper, and can improve oil resistance, abrasion resistance, hand feeling, printability and gloss. It can also be used for printing paper, which can make the paper surface quality good, the ink stable, and the back without cracks. It can also be used in azide paper to produce excellent blueprint paper, which can be used in coated paper to replace titanium dioxide.

Adding 1-2% fumed silica products can reduce the weight of the paper, and the paper is thin, which can improve the strength, prevent ink penetration, and make the printed text clear and increase the opacity.

Overview of the application fields of nano-silica