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Anti ultraviolet textiles

Abstract: with the continuous development of science and technology and the continuous strengthening of human self-protection consciousness, people have clearly realized that skin is a weak link of human body, which is vulnerable to various external factors, and also easy to become a channel for various harmful factors to invade the human body, so it is a defense line that must be paid attention to. In recent years, due to air pollution, the ozone layer has been damaged, and ultraviolet radiation has increased, causing the incidence rate of skin diseases increasing. Due to the decrease of ozone layer thickness, the short wavelength ultraviolet radiation to the ground increases. Although the ultraviolet rays in the sunlight can make people synthesize vitamins and kill some microorganisms or viruses, the increase of ultraviolet rays and shortwave have great harm and influence on people (including the biological world). To protect human body from excessive ultraviolet radiation has become one of the important goals for many industries to develop new products. In recent years, the emergence of anti ultraviolet clothing and textiles is to adapt to the above situation. Some countries have sold goods, such as blouses, stockings, sportswear, hats, sun umbrellas and so on.

1、 Mechanism of anti ultraviolet fabric

There are three kinds of functions of light and object: transmission, reflection and absorption. The corresponding UV shielding agents are reflectors (or scatterers) and absorbers. They can be used alone or in combination.

Ultraviolet reflectors mainly use the reflection and scattering of inorganic particles to prevent the transmission of ultraviolet rays. The commonly used ultraviolet reflectors are the ultra-fine powder of metal oxide or ceramic powder, metal compounds, such as titanium dioxide, zinc oxide, etc., which are inactive and have low transmittance and high scattering rate in the ultraviolet spectrum region. By using these inorganic particles to reflect and diffuse the incident light, the effect of preventing ultraviolet transmission can be achieved. In addition, these materials can be made into nano-sized ultra-fine powder, and then blended with fiber materials, which can enhance the reflection and scattering of ultraviolet light of fiber materials, so as to prevent and reduce the transmission of ultraviolet light through fiber materials.

Ultraviolet absorbers mainly use organic matter to absorb ultraviolet light and convert energy to consume or release energy in the form of heat or harmless low radiation. The anti ultraviolet textiles made by adding this kind of UV shielding agent into fibers, yarns and fabrics can significantly improve the UV protection ability, and the UV shielding rate is generally more than 90%, some even more than 99%. The commonly used UV Absorbents are salicylate compounds, metal ion compounds, benzoketones and benzotriazoles. Metal ion compounds, often used as chelates, are designed to improve the light resistance of dyes; Salicylates are not widely used because of their low melting point, easy sublimation and short wave absorption wavelength; The price of benzoketones is higher, so benzotriazoles are more used as UV absorbers.

The anti ultraviolet fabric can prevent the ultraviolet rays from penetrating the fabric and irradiating the human skin. At the same time, it can also reduce the ultraviolet effects on the fibers and dyes. Moreover, the wearing properties of the fabric, such as strength, air permeability, rigidity and flexibility, should not be adversely affected, and can meet the use requirements.

2、 Anti ultraviolet method

UV shielding agent: UV absorber, Inorganic UV shielding agent.

2 anti ultraviolet fiber: anti ultraviolet fiber refers to the fiber with anti ultraviolet damage ability or containing anti ultraviolet additives.

2.1 natural anti ultraviolet fiber: acrylic fiber is an excellent anti ultraviolet fiber. In addition, hemp fiber and bamboo fiber also have excellent anti ultraviolet performance. Anti ultraviolet processing of fiber: different fiber should adopt different processing methods: nylon has poor anti ultraviolet ability. Adding a small amount of additives (such as manganese salt and hypophosphoric acid, manganese borate, aluminum silicate and manganese salt 2 cerium salt mixture, etc.) into the polymer of nylon can produce anti ultraviolet nylon. The anti ultraviolet polyester is made by adding ceramic ultraviolet shielding agent into the polyester. For cotton fiber, it can be made by impregnating with ultraviolet absorbent of organic system (such as salicylic acid system, benzophenone system, benzotriazole system, cyanoacrylate system, etc.)

Generally speaking, the UV shielding agent (organic or inorganic) is added in the spinning process, and the blended yarn, core sheath spinning and other spinning methods are used. The fabric made of this kind of fiber is better in style and washability than that of after finishing.

3 fabric finishing

At the beginning of the development of anti ultraviolet fabric, this method is adopted, which can be carried out on the original equipment and is easy to realize. The finishing process can be different according to different uses. For example, as a summer clothing fabric, it has high requirements for softness and comfort, and it is better to use the exhaustion method, printing method or immersion method; As decorative, household or industrial textiles, coating method can be used. There are still some problems in the washing resistance and weather resistance of the finishing method, which need to be improved.

3、 Factors affecting the properties of anti ultraviolet textiles

1 fiber type: because polyester fiber contains benzene ring and wool fiber contains aromatic amino acids, their transmittance to ultraviolet radiation is low, that is, SPF (UPF) value is high. However, cotton fiber and viscose fiber have higher transmittance to ultraviolet radiation, that is, the SPF (UPF) value is smaller.

2 color: the UV transmittance of fabrics with different colors is different, as shown in Table 1

Table 1 UV transmittance of polyester fabrics with different colors

Transmittance

Less than 5%

5%~10%

15%~20%

colour

black

Navy, red, dark green, purple

Green, light red, light green, white

Fabric thickness: the thicker the fabric is, the better its anti ultraviolet radiation performance is. After UV treatment, the SPF (UPF) value of the fabric is greatly increased when it is very thin. If the fabric thickness is increased, the SPF (UPF) value will not increase obviously. The thickness of the fabric is closely related to the quality, density and tightness of the fabric. Table 2 shows the influence of the tightness and thickness of the fabric on the resistance to ultraviolet radiation.

It can be seen that the general rule of textile anti ultraviolet is as follows:

Under the same conditions, short fiber fabric is better than filament fabric; Fine fiber fabric is better than coarse fiber fabric; The micro fiber is better than the ordinary fiber fabric, and the woven fabric is better than the knitted fabric; Dark color is better than light color; In addition, flat anisotropic chemical fiber fabric has circular cross-section.

4、 Evaluation index of ultraviolet radiation

1 sun protection factor (SPF)

Also known as sun protection factor, it refers to the time multiple of skin resisting ultraviolet rays. It is generally used for the grade of sun protection injury, and also for the sun protection factor of fabric. The value is applicable to everyone. The calculation method is: assuming that the intensity of ultraviolet does not change with time, if a person without any sunscreen measures stays in the sun for 10 minutes, his skin will turn red. When he uses SPF30 sunscreen, it means that he can prolong the time by 30 times, that is, his skin will turn red after 300 minutes.

2 ultraviolet protection factor (UPF)

Also known as UV shielding coefficient or anti UV index, it is the ratio of the average amount of UV radiation to unprotected skin and the amount of UV radiation after UV protection finishing. UPF is a widely used index to evaluate the anti ultraviolet property of fabrics abroad. The higher the UPF value, the stronger the UV resistance of the fabric. The SPF (UPF) value of cotton and polyester / cotton blended fabrics commonly used in textiles is generally less than 15. When the fabric is wet, the SPF (UPF) value is lower, even to 5. Therefore, it is necessary to add anti ultraviolet finishing agent on the fabric to improve the SPF (UPF) value of the fabric. According to the national standard published in 2002, when the UPF value of the sample is greater than 30, it can be called anti ultraviolet products.

5、 Evaluation of fabric anti ultraviolet effect

1. UV protection ability of fabric

The evaluation of fabric anti ultraviolet effect should include two aspects: the fabric itself and the protective effect of finishing agent. The fabric itself has a certain degree of UV protection, and its performance is determined by the following factors.

1.1 Fiber Varieties

Including different natural fibers, all kinds of chemical fibers and UV shielding fibers, anti UV fibers. The UV shielding fiber developed recently abroad, sometimes without finishing, also has better protection effect.

1.2 fabric structure

It includes yarn count, density and pore size of knitted, woven or nonwoven fabrics. If the pore size is too large, ultraviolet light is easy to pass through, and it is not conducive to finishing.

2. UV protection index

2.1 UV protection factor UPF value

UPF value refers to the ratio of the erythema ultraviolet radiation dose weighted value of the tester when there is no sample to the erythema ultraviolet radiation dose weighted value of the tester when there is sample.

2.2 SPF value

SPF value refers to the ratio of the minimum amount of erythema required by the protected skin to the minimum amount of erythema required by the unprotected skin.

2.3 UV transmittance

UV transmittance = UV intensity after penetrating fabric / UV intensity without fabric shielding. Among them, "the intensity of ultraviolet radiation after penetrating the fabric" refers to the intensity of ultraviolet radiation after a certain period of time

The ultraviolet light emitted by the inner ultraviolet lamp passes through the fabric and is received by the ultraviolet intensity meter; The "UV intensity without fabric cover" is the energy that the ultraviolet light emitted by the UV lamp is directly received by the UV intensity meter at the same time.

3. Test method of ultraviolet fabric

The test methods of UV protection are generally divided into instrument method and direct method. The instrument method uses spectral radiation, and the test instrument is used for testing; In contrast, the objectivity of direct method is not enough and the repeatability is poor.

3.1 ultraviolet spectrophotometer method

Ultraviolet spectrophotometer method is to use ultraviolet spectrophotometer as the radiation source, the wavelength range is 280 ~ 400nm of ultraviolet, irradiate the fabric, and then use the integrating sphere to collect the radiation flux in all directions through the fabric, and calculate the ultraviolet transmittance. This method has high precision and is widely used in the research process.

3.2 UV intensity accumulation method

Put the tested sample between the ultraviolet lamp and the ultraviolet accumulator, irradiate the tested sample according to the given time, and determine the UV cumulative quantity QS (J / cm2) of the ultraviolet passing through the sample and the UV cumulative quantity QP (J / cm2) of the ultraviolet lamp in the same time, then the UV transmittance is: QS / QP × 100%。

3.3 photochromism

The same photosensitive paper is placed under different fabric samples, and then exposed to sunlight (or artificial light source) for 15 ~ 30s. After fixing, the color of the photosensitive paper is compared. If the color of the photosensitive paper is light, it obviously has less photosensitivity, and the fabric on it has high anti ultraviolet performance.

6、 Application prospect of anti ultraviolet fabric

In the face of more and more serious environmental problems, people not only begin to pay attention to environmental protection, but also pay more attention to their own protection. Anti ultraviolet textiles, like other protective products, have attracted people's attention. There are many kinds of anti ultraviolet textiles. Modern women pay great attention to the maintenance of their skin, for fear that the skin will be damaged by ultraviolet rays, so the market prospect of lightweight women's clothing fabric with anti ultraviolet function in summer is good. In addition to women's clothing fabrics, other such as sunshade hat with anti ultraviolet function and stockings will also be better selling points. Men also have a potential demand for this kind of protective textiles. The market prospect of men's clothing such as T-shirts, shirts, long pants and so on after anti ultraviolet processing is immeasurable. Sportswear and casual wear are often worn outdoors. If they are produced and processed into sportswear and casual wear with anti ultraviolet thread, including swimsuit, tennis shirt, golf suit, ski shirt, T-shirt and so on, It will be another hot spot in the market. The tooling needed for outdoor operation, such as field work clothes, fishery work clothes, agricultural work clothes, also need to have the function of anti ultraviolet. Anti ultraviolet products are not only limited to clothing products, but also have higher requirements for other products such as curtain cloth, advertising cloth, tarpaulin, etc. Therefore, the market prospect of textile products with anti ultraviolet function is very broad [4].

7、 Summary

With the application of nanotechnology in the preparation of UV shielding agent, the development of a new generation of high-performance UV absorber, the improvement and development of anti UV fiber manufacturing technology and finishing technology, and the establishment of standard test method for anti UV effect evaluation, the development of anti UV fiber and its fabric will reach a new level. Nowadays, the anti ultraviolet function has become a concern of clothing. Under the strong sunlight, the traditional textiles can not meet people's requirements. Therefore, it is an important choice for people in areas with strong ultraviolet radiation and outdoor work to use anti ultraviolet textiles to prevent ultraviolet. Moreover, the anti ultraviolet textiles are also in line with the consumption concept of modern people. Its market potential at home and abroad is huge, and it has a good application prospect. Moreover, with the improvement of people's living standards and the further enhancement of health care awareness, the multifunctional anti ultraviolet fabric will have better development value and broad market prospects.

[1] Li Quanming, Wang Hao, et al. Study on anti ultraviolet fabric [J]. High tech fiber and application, 2002,27 (3): 19-21

[2] Wang Xiuling. Antibacterial, deodorizing and ultraviolet absorbing materials obtained from zinc oxide coated fabrics [J]. Printing and dyeing Yicong, 1995, (6): 47-54

[3] Fan Jie. Ultraviolet protection and performance test of textiles [J]. Guangxi Textile Science and technology, 2005, (1)

[4] Huang Liansheng. Anti ultraviolet textiles [J]. Textile guide, 2001, (1)