Development and application of electromagnetic wave shielding fabrics
With the rapid development of science and technology, mankind has entered the information age. Mobile phones, microwave ovens, computers, copiers, televisions, air conditioners and other products have become increasingly popular. These electronic devices and household appliances will produce different wavelengths and wavelengths during use. frequency of electromagnetic waves. Although these electromagnetic waves are colorless, odorless, invisible, and intangible, they have strong penetrating power and great biological effects. They fill the entire space and are difficult to guard against. They have become the fourth largest pollution after air pollution, water pollution, and noise pollution. It is known as “electronic smog”.
According to a survey by the U.S. Environmental Protection Agency, more than 98% of people are often exposed to varying degrees of electromagnetic wave radiation, and pulse radiation of electromagnetic waves can cause damage to the human cardiovascular system, endocrine system, nervous system, reproductive system, and immune system. Functional damage, especially to brain cells, is very damaging. In 1993, Sweden and other three Nordic countries conducted a research survey and announced that people exposed to electromagnetic wave radiation of more than 2mg for a long time are 1.5 times more likely to develop leukemia than normal people. The former Soviet chess master Mingulas died from electromagnetic radiation while playing chess with a supercomputer. Therefore, it is best to use shielding measures for the electromagnetic waves generated to achieve self-protection. For this reason, the development of electromagnetic wave shielding fabrics came into being.
At present, shielding fabrics mixed with metal fibers have already become an emerging product of green textiles required by environmental protection in developed countries, but they have just started in my country. At the turn of the century, China will eventually join the WTO. In order to adapt to the requirements of the international development trend of environmentally friendly textiles, our country is researching and developing shielding fabrics against electromagnetic radiation, which have a wide range of applications in aerospace, military and civilian fields. Market and application prospects.
1. Magnetic waves and their protection
1.1. Overview of electromagnetic waves
From basic physics, we know that there are two types of charges: positive charges and negative charge. Both kinds of charges are the source of power plants. Moving charges create currents, and currents can create magnetic fields. A time-varying electric field will be accompanied by a magnetic field, and a time-varying magnetic field will be accompanied by an electric field. In other words, time-varying electric and magnetic fields couple together to produce an electromagnetic field. The periodically changing electromagnetic field propagating in space is an electromagnetic wave. The electromagnetic wave itself carries electromagnetic energy. The process in which this energy is transmitted from the origin of the electromagnetic wave through space to a certain receiving point at a certain distance is radiation.
Electromagnetic waves include long waves, medium waves, short waves, ultra-short waves and microwaves. For long, medium, short, and ultra-short wave electromagnetic radiation, we use electric field intensity to express it, and for microwave electromagnetic radiation, we use power density to express it. Microwave frequency is 300MHz ~ 300GHz, and the corresponding wavelength is in the range of lm ~ lmm. Microwave has high frequency, wide frequency, large amount of information, short wavelength, high wave directionality and resolution ability. It is used in radar, communications, medical treatment, and food processing. It has been widely used in other fields, but while people learn to use microwaves, the harm caused by microwaves to humans is great in electromagnetic radiation, which cannot be ignored. In March 1996, Japan’s SAPLO magazine published the following reference table of electromagnetic radiation detection data for commonly used household appliances; (unit mg)
1.2. The mechanism of electromagnetic wave radiation on the human body and its hazards
The harm of electromagnetic radiation to humans can be divided into thermal effects and non-thermal effects. Thermal effect refers to the “heating” effect of high-frequency electromagnetic waves on biological cells. After the human body receives electromagnetic radiation, the polar molecules in the body will quickly arrange themselves in an alignment motion as the polarity of the electromagnetic field changes. The molecules collide with each other and generate huge heat due to friction, causing the body to warm up. If a lot of radiant energy is absorbed and the heat cannot be dissipated by regulating body temperature, it will cause the body temperature to rise, which will lead to various adverse symptoms. Non-thermal effects refer to the effects of low-frequency electromagnetic waves. After the human body is exposed to electromagnetic radiation, the body temperature does not rise significantly, but it has interfered with the inherent weak electromagnetic field of the human body, causing changes in blood, lymph and cell protoplasm, causing harm to the human body. For workers who have been exposed to electromagnetic wave radiation for a long time, their systolic blood pressure, heart rate, immune function of platelets and white blood cells will be affected to a certain extent, and symptoms such as neurasthenia, early hair loss, and eye turbidity will occur. Therefore, electromagnetic wave radiation is particularly high. Frequency has a very obvious destructive effect on the human body.
1.3 Protection against electromagnetic waves
In order to reduce electromagnetic radiation, experts warn to stay away from electromagnetic wave emission sources and to use shielding measures for electrical appliances that generate electromagnetic waves. However, a good way is to achieve self-protection, such as Wear shielding coats on microwave radiation sources such as mobile phones, wear shielding protective clothing on people who have been working on computers and copy machines for a long time, and wear shielding aprons on housewives who cook in microwave ovens, especially if they are pregnant with a baby. Pregnant women need more protection in this area.
2. Development of electromagnetic wave shielding fabrics
2.1 Types and properties of shielding fabrics
The types of electromagnetic wave shielding fabrics can be roughly divided into There are three major categories: one is shielding fabric using functional fibers, the other is shielding fabric with radiation protection finishing, and the third is shielding fabric with metal mesh interlayer.
�Judging from the situation, there are still many topics that need further research and we still need to work hard to achieve industrialization and sales. To this end, we have the following suggestions:
(1) For successfully developed products, we should Establish standards as soon as possible, improve product quality and performance, expand external publicity, and open up domestic and foreign markets;
(2) National standards for electromagnetic wave shielding fabrics should be formulated in a timely manner, which is conducive to the standardization and development of enterprises.
(3) At present, only a few people think that electromagnetic waves are harmful to the human body and adopt work clothes. Most people who are close to electromagnetic waves still lack sufficient understanding of this, so marketing efforts should be increased. The state should also formulate corresponding labor protection regulations and promulgate relevant policies based on environmental protection requirements to improve people’s awareness of self-protection.
(4) For metal fiber spinning, there are still problems such as the metal fiber bundle is not easy to draft, drawing and roving are easy to end up, the fine yarn has many thick details, uneven mixing, high breakage rate, etc., high The content of spinning is even more obvious, so we should further explore the technology, improve the quality of spinning, increase production efficiency, and reduce processing costs.
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