Far-Infrared Properties And Testing Of Textiles

1 development of far infrared textiles

In the field of textile and clothing, the developed countries such as Japan, the United States, Germany and Russia were the first to carry out the development.

China began developing far-infrared textiles in 1990s.

The Jiangsu Textile Research Institute has developed far infrared polyester staple.

At present, the far-infrared textiles developed mainly use ultrafine ceramic powders as additives to prepare far-infrared fibers in spinning solution, or finishing liquid made of ceramic powder.

The main application of ceramic powder: metal oxides, such as Al2O3, TiO2, BaO, ZrO, SiO2, etc.; metal carbides, such as SiC, TiC, ZrC, and so on, metal nitride, such as BN, AlN, ZrN and other AlN.

2 the mechanism of far-infrared textiles

2.1 far-infrared ray

Infrared is located between visible and microwave, and the wavelength range of infrared is very wide. It will be divided into three wavelengths in science: near infrared band: 0.77~3 m; mid infrared band: 3~30 m; far infrared band: 30~1000 m.

Due to the narrow range of the mid infrared band, the mid infrared band is incorporated into the far infrared band [4] in the field of health care.

2.2 mechanism of action

Thermal radiation is a heat pfer method characterized by the pmission of energy in the form of electromagnetic waves.

Thermal radiation mainly includes ultraviolet, visible and infrared rays.

According to Kirchhoff's law, a good radiator must be a good absorber, that is, the ability of an object to radiate heat is strong, and its absorption capacity is also strong, which is directly proportional to the two.

The human body can radiate far infrared rays and absorb far infrared radiation.

As the body 60%~70% is water, according to the matching absorption theory, when the wavelength of infrared radiation corresponds to the absorbed wavelength of the irradiated object, the molecules of the body absorb resonance.

The main wavelength of the thermal radiation emitted by the human body is about 10 m. Far-infrared textiles radiate the far-infrared rays of 3~25 m after absorbing the external energy, which is consistent with the infrared rays absorbed by the human body, and can form resonance.

Far infrared textiles absorb the infrared wave energy from human body and feed them back to the human body, which improves the skin temperature and achieves the purpose of heat storage and warmth retention.

The heat absorbed by the skin can be pferred through the medium and blood circulation, so that the heat energy reaches the body tissue to achieve the health care and auxiliary medical effect [4].

Far infrared textiles generally improve the pmitting power by increasing the surface emissivity.

2.3 function

Far infrared textiles mainly contain [3], such as warmth retention function, health care function and antibacterial function.

Far infrared textiles, due to the addition of far infrared radiation materials with high emissivity, their thermal insulation performance is to use the thermal radiation of organisms to absorb and store the energy of external radiation to organisms, so that organisms can produce "greenhouse effect" to prevent heat loss and good thermal insulation effect.

Therefore, far-infrared fabrics have remarkable thermal insulation function and are suitable for making winter clothing with cold resistant fabric and light weight.

The heat absorbed by the skin can make the heat energy reach the body tissue through the medium and blood circulation, and can promote the circulation and metabolism of the human body. It has the functions of eliminating fatigue, restoring physical strength and relieving pain symptoms, and has certain auxiliary medical effect on body inflammation.

Therefore, far infrared products have certain symptoms improvement and adjuvant treatment effects on diseases caused by blood circulation or microcirculation disorders.

Suitable for making underwear, socks, bedding, kneecap, elbow protector, wrist protector and so on.

The addition of particulates in fiber can make the fiber surface porous, the surface area increased, and the adsorption and diffusion characteristics of surface activity and surface state are improved obviously, so that the product has the functions of sweat absorption, deodorization, sterilization and so on.

The bacteriostatic test showed that far infrared textiles had a bacteriostasis rate of 95% against Staphylococcus aureus, Candida albicans, E. coli and other pathogens.

3 test methods and related standards

3.1 standard

At present, the functional testing standards for far-infrared textiles are mainly national standard GB/T18319 - 2001, test methods for infrared thermal storage and thermal insulation of textiles, textile industry standard FZ/T64010 - 2000 far-infrared textiles, China Standard Association standard CAS115 - 2005 health care functional textiles.

The GB/T18319 - 2001 standard stipulates that the infrared reflectance and pmittance of textiles can be determined by infrared radiometer, the absorptivity is calculated, and the heating rate of irradiation is determined by point thermometer.

The test and evaluation of [5] mainly from two aspects of infrared absorptivity and infrared radiation heating rate

The FZ/T64010 - 2000 standard stipulates the technical requirements of far infrared textiles, test methods, inspection rules, results determination and usage description.

This standard uses the normal emissivity as the evaluation index of far-infrared textile far-infrared function, and deducts the normal emissivity of the contrast sample (the corresponding non far infrared product) with the normal emissivity of the sample as the normal emissivity to raise the value.

The experimental instruments are infrared spectrometer and blackbody furnace.

The normal emissivity calculated at last is the normal emissivity [6] of 8~15 M band.

CAS115 - 2005 standard adopts the method of determining the normal emissivity, and has developed the far infrared function evaluation index. It is the only standard applicable to health care functional textiles in China at present. Among them, the part of the textile with far infrared function has standardized its terminology definition, test method, result judgement and sign, etc. it is suitable for the far-infrared normal emissivity detection of far-infrared normal materials with various emissivity of more than 0.2 and heat conduction objects.

The normal emissivity of the sample is measured by the method of sample temperature at 100 C, comparing the full radiation brightness with the standard blackbody method at the same temperature to the full radiance.

The test instruments include infrared spectrometer (or infrared radiometer) and blackbody furnace.

The computer processed the radiant intensity of the blackbody furnace, the radiance of the sample and the radiance of the contrast sample, and calculated the normal emissivity [7] of the 4~16 M band.

The comparison of the three standards is shown in Table 1.

{page_break} standard domain property wavelength range technology requires washing performance

FZ/T 64010-2000 industry standard product standard

The increase of the normal emissivity of 8~15 / M far-infrared textiles should be more than 8%.

After 10 times of washing and finishing, the normal emissivity should be more than 7%.

GB/T 18319-2001 national standard method standard 0.8~10 mu m -

CAS115-2005 Association standard product standard

The increase of the normal emissivity of 4~16 m should not be less than 0.08, and its normal emissivity should not be less than 0.80. After 30 times of washing, the increase of the normal emissivity should not be less than 0.06.

Table 1 Comparison of three standards

3.2 test indicators and methods

The main function of far-infrared textiles is thermal insulation, so its thermal insulation performance is the main test index.

For far infrared textiles, the index of far-infrared performance is mainly emissivity and temperature rise.

The main indicators of health function are blood microcirculation.

Health indicators are additional functions only when they are required.

3.2.1 emissivity

As long as it is not absolute zero, any object can radiate infrared electromagnetic waves.

The index of far-infrared radiation energy is radiation power and radiance. But in practical applications, emissivity is often used to characterize it.

Emissivity refers to the ratio of radiated power (or radiance) of a sample to the radiative power (or radiance) of a blackbody at a certain temperature within a wavelength interval.

The emissivity is a positive number between 0~1.

The general emissivity depends on material properties, environmental factors and observation conditions.

The emissivity can be divided into hemispherical emissivity and normal emissivity.

The hemispherical emissivity is divided into hemispherical total emissivity, hemispherical integral emissivity and hemispherical spectral emissivity. The normal emissivity is divided into normal total emissivity and normal spectral emissivity.

At present, the far-infrared performance of products is measured by normal emissivity in the world.

The far-infrared emissivity was determined by Fourier pform infrared spectroscopy.

There is no uniform test method in China. The spectral emissivity of Tianjin determination method and the total emissivity of Shanghai are [8].

A blackbody is an object that absorbs any radiation at any wavelength without any reflection.

According to Kirchhoff's law of radiation, at a certain temperature, the blackbody is the largest body of radiation. Its reflectivity is 0, its absorptivity is 100%, and the emissivity equals 1. It can be called a complete radiator.

There is no real blackbody in reality, it is only approximate.

The emissivity of an object is related to temperature. The temperature must be specified when describing the emissivity of the fabric.

3.2.2 temperature rise method

Temperature rise method is used to measure the change of fabric temperature under certain conditions and time. The temperature rise method is simple and can directly reflect the temperature rise of fabrics.

The temperature rise method includes infrared thermometer method and stainless steel pot method.

Infrared thermometer means that the same temperature, 20 humidity and 60% relative humidity are used to irradiate common fabrics and far-infrared fabrics of the same specification and structure. The temperature of two fabrics at different time intervals is irradiated by infrared light, and then the difference is found. The stainless steel pot means a stainless steel cylinder with a height of 30cm and a volume of 250mL. The upper and lower bottom of the cylinder is made of foam plastic, and the thermometer is inserted on the cover. The fabric is coated outside the stainless steel cylinder, and the temperature of two fabrics is measured under the illumination of the infrared lamp, and then the difference is [2].

Zhang Ping [9] used the fabric with different concentration finishing liquid and the far-infrared fabric with different fabric structure to conduct temperature rise test. In the pure cotton plain cloth sample, the higher the concentration of the finishing agent, the faster the temperature of the sample changes with time.

The results show that the temperature rise method reflects the thermal effect of far-infrared fabrics absorbing far-infrared rays.

3.3 far infrared function evaluation

For the functional evaluation of far-infrared textiles, we should set up an evaluation system with emissivity as the main body and temperature rise and human test as auxiliary.

The functional evaluation of fabrics can be carried out in the following aspects: first, directly test the emissivity of textiles; two, use external means to effect textiles, and test their changes, such as temperature rise method; three, human body test method, fabric and human body function, test the effect on human body [10].

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4 Conclusion

Since the twenty-first Century, the far-infrared functional textiles industry has developed rapidly and has a wide variety of products. However, the industry has been short of technical specifications and related standards. There is no uniform standard for far-infrared textiles evaluation.

Therefore, it is necessary to strengthen basic research on far-infrared textiles testing methods and evaluation criteria.

Reference

[1] Shen Guoxian, Zhao Lianying. Discussion on the physiological effects of far-infrared textiles [J]. modern textile technology, 2011 (1):47-49.

[2] Dong Shaowei, Xu Jing. Research progress and Prospect of far infrared textiles [J]. textile technology progress, 2005 (2):10-12.

[3] research and application of Zhang Fuli far-infrared textiles [J]. naval medicine, 1999,20 (2):154-156.

[4] Zhang Weihua, Zhang Ping, Wang Wei. Far-infrared textiles performance and testing research [J]. dyeing and finishing technology, 2009,31 (9):36-39.

[5]GB/T18319 - 2001 test method for infrared thermal storage and thermal insulation of textiles [S].

[6]FZ/T64010 - 2000 far-infrared textile [S].

[7]CAS115 - 2005 health care functional textiles [S].

[8] Xue Shaolin, Yan Yuxiao, Wang Wei. Far-infrared textiles and their development and application [J]. Shandong Textile Science and technology, 2001 (1):48-51.

[9] Zhang Ping, Zhang Weihua. Testing and evaluation of far infrared fabric's warmth retention function [J]. Journal of Xi'an Polytechnic University, 2010,24 (1):13-16.

[10] Qin Wenjie, Liu Hongtai, Zhang Yi Xin. Evaluation criteria of far-infrared textile function. [J]. advances in textile technology, 2009 (6):52-56.