I. Electronic packaging materials
Organic electroluminescent device (OELD) is a new type of flat panel display device, which has low turn-on and drive voltage, can be driven by DC voltage, can be matched with LSI, is easy to realize full color, and has high luminous brightness (> 105cd/m2). However, the service life of OELD device cannot meet the application requirements, and one of the technical difficulties to be solved is the packaging material and technology of the device. At present, silicone modified epoxy resin is widely used abroad (Japan, USA, Europe, etc.). ), that is, through the * * * mixing, * * polymerization or grafting reaction between them, the internal stress of epoxy resin can be reduced, intramolecular toughening can be formed, the high temperature resistance can be improved, and the waterproof, oil resistance and oxygen resistance of silicone can be improved, but it takes a long curing time (several hours to several days), so the curing reaction should be accelerated. It is necessary to use curing agent or increase the dosage at higher temperature (above 60℃ to 100℃), which not only increases the cost, but also is difficult to meet the requirements of large-scale device production line for packaging materials (short-time, room-temperature packaging). The fumed silica after surface active treatment is fully dispersed in the matrix of silicone modified epoxy resin sealant, which can greatly shorten the curing time of the packaging material (2.0-2.5h) and reduce the curing temperature to room temperature, thus significantly improving the sealing performance of OELD devices and prolonging the service life of OELD devices.
Second, the resin composite material
Resin matrix composites have the characteristics of light weight, high strength and corrosion resistance. However, in recent years, the material industry and the pillar industries of the national economy have higher and higher requirements for the properties of resin-based composites. How to synthesize high-performance resin-based composites has become an important topic in materials and business circles. The appearance of fumed silica provides a new opportunity for the synthesis of resin-based composites and a new way for the modification of traditional resin-based materials. As long as fumed silica particles can be fully and uniformly dispersed in resin materials, the purpose of comprehensively improving the properties of resin-based materials can be achieved.
1, improving strength and elongation. Epoxy resin is a basic resin material. Adding fumed silica to epoxy resin is completely different from adding coarse silica (white carbon black, etc.) to epoxy resin-based composites. ) in structure. Coarse silica is generally added as a reinforcing agent, which is mainly distributed in the chain of polymer materials. However, fumed silica shows strong activity because of its serious surface coordination deficiency, huge specific surface area and surface hypoxia. It is easy to combine with the oxygen of epoxy cyclic molecules, which improves the intermolecular binding force. At the same time, some fumed silica particles are still distributed in the gaps of polymer chains, showing higher ripples compared with coarse silica particles, thus greatly improving the strength, toughness and ductility of epoxy resin materials added with fumed silica.
2. Improve the wear resistance and smoothness of the material surface. Fumed silica particles are smaller than silica 100- 1000 times. Adding it to epoxy resin is beneficial to wire drawing. Due to the high fluidity and small size effect of fumed silica, the surface of the material is denser and cleaner, the friction coefficient is smaller, and the high strength of nanoparticles greatly enhances the wear resistance of the material.
3. Anti-aging performance. A fatal weakness of epoxy resin matrix composites in the process of use is poor aging resistance, which is mainly due to the medium wave and long wave action of ultraviolet rays in 280-400 nm band radiated by the sun, which has a very serious destructive effect on resin matrix composites, and the degradation of polymer chains leads to the rapid aging of resin matrix composites. Fumed silica can strongly reflect ultraviolet rays, and its addition to epoxy resin can greatly reduce the degradation of epoxy resin by ultraviolet rays, thus achieving the purpose of delaying the aging of materials.
Third, plastics.
Using fumed silica with light transmittance and small particle size can make plastics more dense. After adding silica into polystyrene plastic film, not only the transparency, strength and toughness are improved, but also the waterproof and aging resistance are obviously improved. The hardness, smoothness and aging resistance of plastic steel doors and windows produced by adding a small amount of fumed silica to ordinary plastic PVC have been greatly improved. The common plastic polypropylene was modified with fumed silica. Main technical indicators (water absorption, insulation resistance, compressive residual deformation, flexural strength, etc.). ) all meet or exceed the performance index of engineering plastic nylon 6. Replacing nylon 6 with polypropylene railway fittings greatly reduces the product cost and has remarkable economic and social benefits.
Fourth, paint.
China is a big producer and consumer of coatings, but at present, domestic coatings generally have shortcomings such as poor suspension stability, poor thixotropy, poor weather resistance and poor washing resistance, which leads to the need to import a large number of high-quality coatings every year. Some coating manufacturers in Shanghai, Beijing, Hangzhou, Ningbo and other places dare to innovate and successfully realize the application of fumed silica in coatings. This nano-modified coating has changed the shortcomings of previous products, and the main performance indexes have been greatly improved except contrast. For example, the washability of exterior wall coatings has been improved from 1000 to 10000. The artificial accelerated weathering and artificial radiation exposure aging time increased from 250 hours (pulverization 1, discoloration 2) to 600 hours (no pulverization, no discoloration of paint film, color difference value of 4.8). In addition, the bonding strength between the paint film and the wall is greatly improved, the hardness of the paint film is significantly increased, and the surface self-cleaning ability is also improved.
Verb (abbreviation of verb) rubber
Rubber is an excellent elastic body, but its comprehensive 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 its strength, wear resistance and aging resistance. However, due to the addition of carbon black, the product is all black and the grade is not high. The advent of fumed silica in China laid a material foundation for the production of a new generation of rubber products with novel colors and excellent properties. After adding a small amount of fumed silica to ordinary rubber, the strength, wear resistance and aging resistance of the product reach or exceed those of high-grade rubber products, and the color can remain unchanged for a long time. The wear resistance, tensile strength, bending strength and aging resistance of nano-modified color EPDM waterproofing membrane are obviously improved, with bright colors and excellent color retention effect. The development of colored tires has also made some progress. If the bending performance of sidewall rubber is improved from 654.38+10,000 times to more than 500,000 times, it is expected to realize the colorization of domestic automobile and motorcycle tires in the near future.
Six, Yan (dye) material
Although organic pigments (dyes) have bright colors and strong coloring power, they are generally inferior to inorganic pigments in light resistance, heat resistance, solvent resistance and migration resistance. By adding fumed silica to modify the surface of organic pigment (dye), not only the anti-aging performance of pigment (dye) is greatly improved, but also the indexes such as brightness, hue and saturation are improved to some extent. The performance can be comparable to that of imported high-grade products, which greatly broadens the grade and application scope of organic pigments (dyes).
Seven, ceramics
Adding fumed silica instead of fumed alumina in 95 porcelain can not only play the role of nanoparticles, but also be second-phase particles, which not only improves the strength and toughness of ceramic materials, but also improves the hardness and elastic modulus of materials, and its effect is more ideal than adding A 1203. Using fumed silica composite ceramic substrate not only improves the compactness, toughness and flatness of the substrate, but also greatly reduces the sintering temperature. In addition, the application effect of fumed silica in ceramic products such as ceramic filters and corundum balls is also very remarkable.
Eight, sealant, adhesive
Sealants and adhesives are important products with large quantity, various types and wide application range. It requires the viscosity, fluidity and curing speed of the product to reach the best state. China's products in this field are relatively backward, and high-grade sealants and adhesives rely on imports. Foreign products in this field have used nano-materials as modifiers, and fumed silica is the first choice. It mainly coats the surface of fumed silica with a layer of organic matter to make it hydrophobic. When it is added to sealant, the silica structure is quickly formed, that is, the small particles of fumed silica form a network structure, which inhibits the colloid flow, accelerates the curing speed and improves the bonding effect. Due to the small particle size of fumed silica, the sealing and impermeability of the product are also improved.
Nine, 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 fumed silica to gel coat resin by ultrasonic dispersion method. Compared with gel coat without fumed silica, it was found that its Mohs hardness increased from 2.2 (equivalent to gypsum hardness) to 2.8~2.9 (third-grade natural marble hardness), and its wear resistance increased by 1 ~ 2 times. Due to the grafting and bonding between nanoparticles and organic polymers, the toughness of materials has been improved.
X. drug carrier
With the rapid growth of municipal solid waste (MSW) and the increasingly serious environmental pollution, it is urgent to intensify the efforts to eliminate the "four pests" and prevent the spread of diseases. Spraying lime on the trunk and chemicals into the garbage can has little effect. At present, central nervous system anesthetics have been used to kill mosquitoes, flies, cockroaches and other pests in big cities. However, most of these pesticides are imported from abroad, which are expensive and have a short validity period (only one month). Vapor-phase silica as a carrier for adsorbing such pesticides has a good slow-release effect. After determination, the validity period after spraying is more than one year.
XI。 cosmetics
For cosmetics, strong ultraviolet shielding ability is required, and it is best to protect both UVB and UVA. In essence, ultraviolet shielding includes two aspects, one is the absorption of ultraviolet mentioned above, and the other is the reflection of ultraviolet. At present, there is no international report on the development of anti-ultraviolet agents from the perspective of ultraviolet reflection performance. In the past, organic compounds were mostly used as ultraviolet absorbers in sunscreen products, but in order to protect the skin from ultraviolet rays as much as possible, some problems such as skin cancer and chemical allergy will appear after increasing the dose. Fumed silica is an inorganic component, which is easily compatible with other components of cosmetics, non-toxic and tasteless, and does not have the above problems. In addition, it is white and can be simply colored. Especially valuable is that fumed silica has strong ultraviolet reflection ability and good stability, and is not exposed to ultraviolet radiation. These outstanding characteristics of fumed silica have laid a good foundation for the upgrading of sunscreen cosmetics.
Twelve. Antibacterial material
Using the huge specific surface area, porous surface structure, super adsorption capacity and unique physical and chemical characteristics of fumed silica, functional ions such as silver ions were uniformly designed into the mesopores on the surface of fumed silica and realized stably. Nano-antibacterial powder with high efficiency, long-term, high temperature resistance and broad-spectrum antibacterial activity (particle size is only about 70 nm) has been successfully developed, which not only fills the domestic gap, but also reaches or exceeds similar products in Japan. Tests show that when the concentration of nano-antibacterial powder in water is only 0.3 15%, the antibacterial ability to gram-positive representative strains and gram-negative representative strains can be clearly displayed, and the bacteriostatic circle appears 2-3 mm, and with the increase of the concentration of nano-antibacterial powder in water, the bacteriostatic circle increases obviously. According to the determination, when the content of Ag+ in water is 0.0 1mg/ 1, Escherichia coli in water can be completely killed, and no new flora will be produced for 90 days. Nano-antibacterial powder was applied to enamel glaze to make a drum washing machine with mildew-proof and antibacterial function, and its antibacterial rate was as high as 99%. It should be pointed out that the application conditions of nano antibacterial powder in enamel glaze are harsh, and it must maintain strong antibacterial performance in high alkaline liquid and after firing porcelain at high temperature (about 900℃), which is beyond the reach of other antibacterial powders. Nano-antibacterial powder was added to the interior wall coating to prepare the interior wall coating with long-term antibacterial and mildew-proof functions. Nano-antibacterial powder is used in women's underwear detergent, wool, cashmere detergent, detergent and hand sanitizer, and its antibacterial performance is very remarkable after testing by health and epidemic prevention departments. It can be predicted that with the enhancement of people's health awareness, nano-antibacterial powder will gradually be accepted by the general public in related application enterprises, and it will emerge in industries such as bills, medical care, chemical building materials, household appliances, functional fibers and plastic products.
Thirteen. others
1, Application in Optical Field Nanoparticles are used as infrared reflective materials, mainly made into thin films and multilayer films. Nano-particle film materials have a good application prospect in the light bulb industry. High-pressure sodium lamps and iodine arc lamps for photography and video recording all need strong illumination, but 69% of the energy after filament heating is converted into infrared rays, which shows that a considerable part of electric energy is converted into heat energy and consumed, and only a small part 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 luminous efficiency and increase illumination has always been a key problem to be solved urgently. The birth of nanoparticles provides a new way to solve this problem. Since 1980s, researchers and technicians have made multilayer interference films with fumed silica and nano titanium dioxide particles, with a total thickness of microns, lining the inner wall of the bulb cover. Therefore, it not only has good light transmittance, but also has strong infrared reflection ability. According to experts' calculation, compared with traditional halogen lamps, this lamp can save electricity by 15%.
2. PMMA, a new plexiglass additive, is often used as window material of aircraft. When the plane flies at high altitude, the window material is easy to age due to ultraviolet radiation, which leads to the decrease of transparency. In order to solve this problem, using its strong ultraviolet reflection performance, fumed silica with surface modification was added in the production process of plexiglass, and the ultraviolet radiation resistance of the produced products was more than doubled, and the impact strength was increased by 80%.