Application of fumed silica (1)


1. Electronic packaging materials
Organic electroluminescent device (OELD) is a new type of flat display device newly developed. It has low on-drive and low-drive voltage, and can be driven by DC voltage. It can be matched with large-scale integrated circuits, and it is easy to realize full color and brightness. High (>105cd/m2), but the service life of OELD devices can not meet the application requirements. One of the technical difficulties to be solved is the packaging material and packaging technology of the device. At present, foreign countries (Japan, the United States, Europe, etc.) widely use silicone-modified epoxy resin, that is, through the blending, copolymerization or grafting reaction between the two, it can reduce the internal stress of epoxy resin and form molecules. Internal toughening, improve high temperature resistance, and also improve the waterproof, oil and oxygen resistance of silicone, but it requires a longer curing time (a few hours to several days), to accelerate the curing reaction, it needs to be higher Temperature (60 ° C to 100 ° C or higher) or increase the amount of curing agent, which not only increases the cost, but also difficult to meet the requirements of large-scale device production line packaging materials (time is short, room temperature package). The surface-treated gas phase white carbon black [2] is sufficiently dispersed in the silicone-modified epoxy resin encapsulant matrix, which can greatly shorten the curing time of the encapsulating material (2.0-2.5 h), and the curing temperature can be Lowering to room temperature significantly improves the sealing performance of OELD devices and increases the lifetime of OELD devices.

2, resin composite materials
Resin-based composite materials are light, high-strength, and corrosion-resistant. However, in recent years, the material industry and the national economy pillar industries have higher requirements for the performance of resin-based materials. How to synthesize high-performance resin-based composite materials has become An important topic in the current material and business world. The advent of fumed silica has provided a new opportunity for the synthesis of resin-based composites, providing a new way for the modification of traditional resin-based materials, as long as the gas-phase silica particles can be fully and uniformly dispersed into the resin. In the material, the purpose of comprehensively improving the performance of the resin-based material can be fully achieved.
1. Improve strength and elongation. Epoxy resin is the basic resin material. The fumed silica is added to the epoxy resin. The structure is completely different from the epoxy resin-based composite material added by coarse-grained silica (white carbon black, etc.), coarse-grained SiO2. Generally added as a reinforcing agent, it is mainly distributed in the chain of polymer materials, and the gas phase white carbon black is extremely strong due to the serious surface coordination, large specific surface area and surface under oxygen. The activity is easy to bond with the oxygen of the epoxy ring molecule, which improves the bonding force between the molecules. In the same fashion, a part of the vapor phase white carbon black particles are still distributed in the voids of the polymer chain, and the coarse crystal SiO2 particles are phased. Compared with the high flowability, the strength, toughness and ductility of the epoxy resin added by the fumed silica are greatly improved.
2. Improve wear resistance and improve the surface finish of the material. The fumed silica particles are 100-1000 times smaller than SiO2, and are added to the epoxy resin to facilitate the drawing into filaments. Due to the high fluidity and small size effect of the gas phase white carbon black, the surface of the material is more dense and fine, the friction coefficient becomes smaller, and the high strength of the nanoparticles makes the wear resistance of the material greatly enhanced.
3. anti-aging performance. A fatal weakness in the use of epoxy resin matrix composites is the poor anti-aging performance. The main reason is the ultraviolet and long-wave effects of solar radiation in the 280-400 nm band. Its damage to resin-based composites is very serious. The degradation of the polymer chain causes the resin-based composite material to age rapidly. The fumed silica can strongly reflect the ultraviolet rays, and the addition of the epoxy resin can greatly reduce the degradation of the epoxy resin by the ultraviolet rays, thereby achieving the purpose of delaying the aging of the material.

3, plastic
The use of fumed silica is light-transmissive and has a small particle size, which makes the plastic more compact. After adding fumed silica to the polystyrene plastic film, it not only improves its transparency, strength and toughness, but also has waterproof and anti-aging properties. Significantly improved. The hardness, smoothness and anti-aging properties of plastic steel doors and windows produced by adding a small amount of fumed silica to ordinary plastic polyvinyl chloride are greatly improved. The general plastic polypropylene is modified by gas phase white carbon black. The main technical indexes (water absorption, insulation resistance, compression residual deformation, flexural strength, etc.) meet or exceed the performance index of engineering plastic nylon 6, and the polypropylene railway is realized. The replacement of nylon 6 for accessories has greatly reduced the cost of the product, and its economic and social benefits are remarkable.

4, paint
China is a big country in the production and consumption of paints. However, the current domestic coatings generally have shortcomings in performance, such as poor suspension stability, poor thixotropy, poor weather resistance and poor scrubbing resistance, resulting in the import of a large number of high quality coatings every year. Some paint 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 defects of previous products and tested its main performance indicators. Except for the contrast ratio, the rest have been greatly improved. For example, the scrub resistance of exterior wall paint has been increased from more than 1,000 times to more than 10,000 times. The artificial accelerated weathering and artificial radiation exposure aging time is 250 hours ( Powdered grade 1, discoloration grade 2) increased to 600 hours (no powdering, no discoloration of the paint film, color difference 4.8), in addition, the bonding strength between the coating film and the wall is greatly improved, the hardness of the coating film is significantly increased, and the surface self-cleaning ability Also improved.

5, rubber
Rubber is an elastic body with excellent stretchability, but its comprehensive performance is not satisfactory. In the process of producing rubber products, carbon black is usually added to the rubber to improve strength, wear resistance and aging resistance, but The addition of black makes the products black and the grade is not high. The advent of fumed silica in China 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 fumed silica to ordinary rubber, the strength, wear resistance and aging resistance of the product meet or exceed the high-grade rubber products, and the color can be kept unchanged for a long time. The nano-modified color EPDM waterproofing membrane has obvious improvement in wear resistance, tensile strength, folding resistance and anti-aging property, and has bright colors and excellent color retention effect. The development of color tires has also made some progress. For example, the flexural performance of the tire side rubber has been improved from 100,000 times to more than 500,000 times. It is expected that in the near future, the colorization of domestic and motorcycle tires will be realized.

6, color (dyeing) material
Although organic pigments (dyed) have bright colors and strong tinting strength, they are generally inferior to inorganic pigments in light, heat, solvent and migration resistance. The surface modification treatment of organic pigments (dye) by adding fumed silica not only greatly improves the anti-aging properties of pigments, but also improves the brightness, hue and saturation. It can be compared with imported high-end products, which greatly broadens the grade and application range of organic pigments.