1. Definition of thermal shrinkage material
Thermal shrinkage materials, also known as macromolecular shape memory materials, these materials such as polyethylene, polyethylene, and other materials are usually linear structure, after radiation or chemical effects into a network structure, known as cross-linking, cross-linking with the principle of "memory effect" produced a new type of macromolecular functional materials.
The so-called "memory effect", is the radiation crosslinked polyethylene crystalline or non-crystalline polymers, such as when heated to above the melting point, although grain melting, but it doesn't appear flow state, and has a kind of elastic rubber, if this time expand polyethylene, remained expansion cooling finalize the design after the state, if this kind of expansion of polyethylene reheated to the melt crystallization temperature, the polymer material will be from "memory" not expansion of its original form and shrink back again, therefore calls "shape memory effect".
2. Properties of thermal shrinkage materials
This excellent "memory" property can be used to make heat shrink tubes, film and profile materials, which can achieve a radial shrinkage of 50% to 80%. The main characteristic of thermal shrinkage material is that it can be used as insulation, moisture-proof, sealing, protection and connection.
3. Application of thermal shrinkage materials
According to the characteristics of the product, it can be applied in various fields such as energy, electricity, transportation, industry and mining. As this material has the characteristics of simplicity and reliability in the process, it has the function of upgrading in various fields, challenging the traditional industrial products, and has a strong market competitiveness.
At present, the main heat-shrinkable products in China include: heat-shrinkable communication cable accessories, heat-shrinkable power cable accessories, heat-shrinkable sleeve of electronic system, heat-shrinkable cladding sheet, heat-shrinkable insulation heat-shrinkable belt, etc. In terms of output value, heat-shrinkable products now occupy the first place in the radiation processing industry, accounting for about 55% of the total output value of radiation processing. Although output value index contains the contribution of gamma ray processing, the electron beam processing of accelerator, however, is the real foundation of the industrialization of heat-shrinkable materials.
4. Overview of foreign development
In the 1950s, Dole and Charlesby successively found that high-energy radiation could cross-link polyethylene and lead to the improvement of material properties. Later, Charlesby further found that the cross-linked crystalline polymer had a "shape memory effect", thus laying the foundation for the development of heat-shrinkable polymer materials. In 1959 he and Pinner for rui kai (Raychem) company applied for the patent of the first PE heat shrinkable tube, opening a new era of a new type of functional material, can say the United States started with Raychem company is mainly manufacturing heat shrinkable material in radiation processing factories and joint companies, now has grown to nearly 8000 employees, integrated product development boom contraction of more than 3000 kinds of specifications character subsidiaries all over the world, its annual output value of nearly $3 billion. Products are widely used in military industry, electronics industry, automobile industry, power system, communications, petrochemical industry and other fields, and have monopolized most of the international market. Due to the wide application of thermal shrinkage materials, it has been taken seriously in some developed countries, and many western countries, as well as Asian countries such as Japan and South Korea, have also started production. For example, sumitomo electric power co., ltd. of Japan has given priority to the production of heat shrinkable materials for the automotive industry and household appliance industry, with a production value of nearly $100 million. Then tengcang, the same sell started production. The bigger companies are 3M in dollars, Westinghouse and others. South Korea's gold star, the former Soviet union and Europe's Netherlands, Britain, France and Sweden all have large-scale production, but these companies have a single variety of products, far less than Raychem comprehensive development capacity, variety, coverage. The market of heat-shrinkable materials is still in the period of youthful development at present. As heat-shrinkable materials are high-tech products with high profits and good benefits, international competition is becoming increasingly fierce.
5. Domestic development overview:
In late 1950s, the first macromolecular radiation chemistry laboratory was established in changchun yinghua institute of Chinese academy of sciences for basic research. In the 1960s, research on thermal shrinkage materials and radiation crosslinking of wires was started and successfully applied to the "Oriental red" satellite. In order to develop the radiation processing industry, the first radiation pilot test base (the predecessor of jilin radiation chemical industry co., LTD.) was constructed, which laid the foundation for the development and production of thermal shrinkage materials in China.
In the early 1970s, changchun institute of applied chemistry actively undertook the anti-corrosion work of petroleum pipeline in the national "August 3rd" project, carried out the research on radiated crosslinked polyethylene sheet, belt and film, and applied it to the anti-corrosion project of petroleum oil pipelines.
In the early 80 s, led by should change, united jilin wheel, water and electricity of wuhan by high pressure, is commissioned by the national science and technology commission, water and electricity department and support, completed the power cable of attack of the heat shrinkable accessories is poor, and rapidly promote the use, broke the situation of unify the whole country, Raychem products promoted the formation and development of high-tech industry in our country. In the mid-1980s, changchun yinghua institute built a factory to produce, and in 1994 established changchun heat shrinkable materials co., LTD. (CIAC), laying a foundation for industrialization and scale.
Since 1987, the number and varieties of heat-shrinkable products in China have developed rapidly. The main reason is the high added value of thermal shrinkage materials to manufacturers incentives; The demand for civil and public utilities construction shows the potential market of new materials. The involvement of Raychem, an American company, affected the main manufacturers in China, forced large manufacturers to be associated with one another, and small factories to form a "heat shrink and heat" situation in China. Due to the development history, domestic heat-shrinkable materials are mainly limited to two series of communication cable accessories and force cable accessories. At present, there are basically two major patterns: one is the communication product manufacturer cluster represented by sichuan shuangliu and the other is the force cable accessory manufacturer cluster represented by changchun CIAC. According to incomplete statistics, there are more than 300 enterprises, large and small, of which 63 have good product quality and efficiency.
There are 7 units specialized in the production of heat-shrinkable materials in China (a total of 10 units are used, accounting for about 22% of the total number of accelerators). Another nine produce both heat shrinkable products and cables (each supposedly accounts for 10% of the total number of accelerators). As a result, about 32% of the total irradiation accelerator is used in the production of heat-shrinkable products.
Although there are many domestic factories, there are only a dozen with relatively large scale and high level. The domestic market is basically monopolized by several big factories, including Raychem.
In 1994, the total output value of thermal shrinkage materials reached 500 million yuan, and in 1995, the total output value was nearly 600 million yuan, and the profit and tax value was 200 million yuan. At present, the main heat-shrinkable products in China include: heat-shrinkable communication cable accessories, heat-shrinkable power cable accessories, electronic system heat-shrinkable sleeve, heat-shrinkable cladding sheet, composite insulation heat-shrinkable belt and so on. In terms of output value, heat-shrinkable products now occupy the first place in the radiation processing industry, accounting for about 55% of the total output value of radiation processing. Although output value index contains the contribution of gamma ray processing, the electron beam processing of accelerator, however, is the real foundation of the industrialization of heat-shrinkable materials.
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