Characteristics of nano-kaolin and its application prospects

I. Introduction

Nanoclay is currently a research hotspot in the world. This is typical of nylon 6/layered montmorillonite nanocomposites developed and industrialized by Toyota Central Research Institute of Japan. Many researchers in the Institute of Chemistry of the Chinese Academy of Sciences, Beijing University of Chemical Technology, Sichuan University and other universities and research institutes have done research in this area ^[2] , and have achieved remarkable results, but have not successfully obtained large-scale industrial applications in China.

At present, from the research and production status of nano-clay composite materials at home and abroad, most of them use montmorillonite as raw material for producing nano-clay, and adopt the method of intercalation and recombination. However, this method is complicated in process and high in production cost, so that it can be popularized and applied. restricted. In addition, the intercalation recombination method has a small selectivity of raw materials, and is mainly studied in the field of plastics, and is less studied in other fields such as rubber. If nano-clay powder is produced, it can be easily integrated into the traditional plastic or rubber polymer production process, which will undoubtedly have great market application potential and strong vitality.

Since kaolin has a higher whiteness than montmorillonite clay, the surface of the crystal layer is charge neutral (the smectite layer has a higher negative charge), and the kaolin clay deposit usually contains less impurities than the smectite clay deposit, so The former produces nanoclay with greater advantages than the latter, for example, it can be better used for white or light-colored rubber and plastic, white and light-colored paints, and low cost.

Second, the main properties of nano-kaolin

Shandong Zaozhuang Sanxing High-tech Materials Co., Ltd. is currently the only enterprise producing nano-kaolin in China and has reached large-scale industrial production. The performance indicators of its industrial products are shown in Tables 1 and 2. It can be seen that this kaolin has a high purity and is almost composed of kaolinite. The kaolinite sheet has an average particle size of 300-500 nm and a sheet thickness of less than 100 nm. According to the definition of nanomaterials: materials with at least one dimension in the dimension of 1-100 nm can be called nanomaterials. The kaolinite layer thickness of this product is on the order of nanometers, so it is a two-dimensional layered nanomaterial. It can also be seen from Table 2 that this product has a high specific surface area, excellent suspension and dispersion properties. The dispersed suspension hardly precipitates for several months at rest.

Table 1 Chemical composition of nano-kaolin

Table 2 Physical properties of nano-kaolin

Third, the main application areas of nano-kaolin (Applications of Nanokaolin)

1. Application in Rubber (Application in Rubber)

The product can be used in a variety of rubber products to significantly improve its mechanical and physical properties while reducing its production costs. In particular, it has advantages in terms of elasticity, flex resistance, barrier properties and elongation at break. It is superior to white carbon black in the properties of butadiene rubber, EPDM rubber, natural rubber and nitrile rubber, and is close to the reinforcing performance of white carbon black in styrene-butadiene rubber. Suitable for tire sidewall rubber, inner tube, golf rubber, rubber wire, nitrile sealing rubber, sole rubber, rubber roller, glue stick, conveyor belt rubber and other products.

Table 3 Reinforcement properties and comparison of nano-kaolin in styrene-butadiene rubber

Table 4 Comparison of reinforcing properties of nano-kaolin and white carbon black in butadiene rubber, EPDM and natural rubber

2, application in plastic (Application in Plastics)

Application in rubber-plastic composites: enhanced and toughened.

Gu Yuanchun, Qiu Guixue and Bao Yan of the Key Laboratory of Rubber Materials and Engineering of Qingdao University of Science and Technology, using the nano kaolin produced by the company as a reinforcing agent, using the new polyolefin elastomer POE as a toughening agent, the traditional elastomer toughening novel method and means to enhance toughening nanoparticle combined technique using alloys and composite filling process, to obtain a polypropylene composite material of high performance. The results show that nano-kaolin and elastomer POE have synergistic effect on PP toughening, which is not a simple addition of independent toughening effect. Nano-inorganic particles have enhanced effect on PP/POE of composite system and greatly slow down. The strength of the composite system is reduced due to the addition of POE. (See Plastics Industry, 2004, Vol. 32, No. 10, pp. 15-17)

General Motors and Monte North America have successfully used nano-kaolin to produce polyolefin thermoplastic elastomer composites that increase their rigidity and toughness. They also use composites containing nano-kaolin for other automotive parts.

Application in engineering plastics

Table 5 Test results of nano-kaolin in polypropylene plastics (filling amount 15%)

Nano-kaolin is used in engineering plastics such as polypropylene, polyethylene, and nylon to impart good heat resistance and mechanical properties to plastics. Can be used as auto parts, oil storage tanks, fuel pipeline systems, electronic connectors, conduits, telephone housings, tool handles, railings, conditioning handles, high-lubrication and low-flow resistance pipes; due to its high rigidity, it can be used Thin-walled structural products reduce quality and cost. Nano-kaolin can also impart good flame retardancy and barrier properties to plastic products.

Application in expanded polystyrene

Researchers at Ohio State University in the United States have found that using only 1% to 2% of nanoclay can increase the compression modulus of expanded polystyrene (EPS) by 25%. Nanoclay has two functions, one as an enhancer for EPS and the other as a nucleating agent.

Application in plastic film

Because nano-kaolin has good barrier properties, it can be used for food preservation packaging and prolong the shelf life of food. It is used in agricultural film to not only increase the mechanical properties of the film, reduce the production cost, but also does not affect its transparency, and its excellent UV barrier properties. It is beneficial to increase the temperature inside the shed. It is used in packaging printed materials to provide excellent mechanical properties and strength, and to impart good sensory properties.

3, Application in Paper (Application in Paper Making)

As a coating material for paper, it can impart high gloss, high whiteness and high strength to printed products and packaging papers, and contribute to structured coating design, achieving higher quality visual effects, gloss effects and printing effects. replace the expensive titanium dioxide. It is a high quality coating material for premium paper and special paper.

4, in the application of ink (Application in print ink)

The printing ink market requires high performance ultrafine powders as functional fillers. Nano-kaolin exhibits excellent dispersibility, excellent gloss and hiding power, excellent ink absorbability and dryness in the ink.

5, Application in paint (Application in paint)

In the coating industry, nano-kaolin is used as a whitening body pigment with excellent suspension stability, and it is not easy to precipitate for a long time. Its fine particles can improve the gloss of the paint, enhance the gloss, dryness and hiding power of the product, and also have a reinforcing effect. Use it to replace the more expensive titanium dioxide, the same effect can be achieved.

6, in the application of adhesive (Application in stickness)

In recent years, adhesives are developing in the direction of special applications such as low viscosity, high strength, impact resistance and flame retardancy. With the demand for higher performance of underwater adhesives, nanofillers are added to epoxy adhesives to greatly improve the adhesive. The strength, wear, corrosion and other properties of the adhesive coating and reduce the cost of the adhesive.

7, used in catalyst carrier (Used as catalyst carrier)

Nanokaolin due to the large specific surface area and adsorption properties, it is therefore useful as synthetic petrochemical industry catalyst carrier has good stability.

8, used as a pesticide carrier (used as pesticide carrier)

Because nano-kaolin has the characteristics of large specific surface area, strong adsorption, strong ion exchange capacity and strong plasticity, it can be used as a carrier for granular pesticides, powder pesticides and liquid pesticides. Using him as a pesticide carrier can not only fully disperse the pesticide, but also enable the pesticide to be slowly released for a long time, so as to prolong the drug period, and at the same time improve the structure of the soil and facilitate the growth of the plant.

9. Application in ceramics (Application in ceramic glaze)

Applying nano-kaolin to the glazed surface of ordinary ceramics not only makes the ceramic glaze smoother, but also enhances the glaze activity, making it easy to clean and has a certain bactericidal function.

10. Application in high strength cement (Application in high quality cement)

In high-strength concrete, adding a small amount (0.5-1.0%) of nano-kaolin can increase the early strength, impermeability and folding resistance by 20-30%, and also can be used as a water reducing agent to improve the fluidity of the slurry.

11. Application in chemical fiber (Application in chemical fiber)

The polyester chips and nylon-sliced ​​kaolin developed by the company are used in polyester fibers, nylon fibers or other fibers due to their fine particle size, and have the advantages of continuous silk and good spinnability. At the same time, it can be used as a functional ceramic powder instead of expensive nano-TiO ₂ as a matting agent, and also has anti-ultraviolet and far-infrared heat preservation functions. Nano-kaolin is used in polyester fibers to improve color rendering properties and improve post-processing properties. The excellent suspension and dispersion properties of nano-kaolin make it particularly suitable for use in wet spinning processes.

Fourth, the conclusion

Nano-kaolin is a newly developed new product in China. Although it has been published for a long time, it has shown strong vitality and broad application prospects. The excellent application performance of this product in different application fields is mainly attributed to its fine particle size; special surface treatment makes it show good dispersion in organic polymer; excellent suspension performance in aqueous solution.

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