1. Ultraviolet light and its effects on the human body
On February 24th, the ultraviolet rays in the sun's rays have been known to be beneficial to the human body for a long time. For example, it can promote the synthesis of vitamin D and promote the development of bone tissue. In outdoor activities, it helps to prevent rickets, is good for your health, and the skin is black and red is a symbol of health and so on. However, modern scientific research shows that the harmful effects of ultraviolet light on the human body are far greater than its beneficial effects. Excessive exposure to UV radiation is harmful. It mainly affects the eyes and skin, causing acute keratitis and conjunctivitis, chronic cataracts and other eye diseases, and induces skin cancer.
There is an ozone layer 25-30 km above the atmosphere, which absorbs excessive ultraviolet rays from the sun, protecting all living things on Earth and our human beings from UV rays. However, in recent years, due to human production and living activities, large quantities of chlorofluorocarbons such as Freon have been emitted, causing the earth's environment and stratospheric ozone to be increasingly severely damaged. The emergence of ozone holes in the Antarctic and Arctic regions, the Earth's The ozone layer of the protection ring is thinned and thinned, and the consequence is that the amount of ultraviolet radiation reaching the ground is increased.
According to the wavelength of the radiation, ultraviolet light can be divided into three bands: ultraviolet A (wavelength 315–400 nm), ultraviolet B (wavelength 280–315), and ultraviolet C (wavelength below 280 cm). Since the atmospheric ozone layer absorbs little ultraviolet A, the ultraviolet A can reach the ground, and the change in the amount of radiation is basically independent of the change of the ozone layer, and the ultraviolet C is completely opposite to the ultraviolet A, which is almost completely absorbed by the ozone layer, so It basically does not reach the ground and the amount of ultraviolet B radiation is closely related to the change of the ozone layer, and has a greater impact on humans.
In recent years, there have been more and more anti-UV fabrics. Generally, ultraviolet ray finishing agents are added to fabrics, and ultraviolet rays are used to process fabrics to prevent ultraviolet rays from harming the human body. Various UV protection fabrics are also on the market.
For processed UV-resistant fabrics, how to test their UV transmittance, what are the current domestic and international testing methods, and their similarities and differences, is a problem that people have been paying attention to. This article makes some comparisons.
2. Test methods and product standards for textiles against UV radiation
Because Australia and New Zealand are more strongly exposed to ultraviolet radiation, people are more concerned about the damage caused by ultraviolet radiation. In 1990 and 1993, Australia and New Zealand introduced standards for sunglasses and sunscreens. In 1996, Australia and New Zealand launched the AS/NZS4399 fabric UV test standard. In 1997, China developed the UV resistance test method for fabrics GB/T17032–1997. The United States and the United Kingdom also introduced the UV transmittance method standards for textiles in 1998, namely AATCC 183–1998 and BS 7914–1998.
In 1997, the UV801 standard (The UV-Standard 801) was proposed by the Hohenstein Institute in Germany to evaluate the UV resistance of textiles, to provide test results and to label qualified textiles with UV radiation. In 1999, the United Kingdom developed BS7949:1999? "Product Standards for Children's Clothing Against UV Radiation Performance", which stipulates that children's tops, shorts and body clothes have an ultraviolet transmission rate of no more than 2.5%. China's standard-setting plan for anti-ultraviolet textiles has also been included in the 2000 bidding plan, which was completed in 2001.
3. Test result representation method
3.1 UV protection factor (UPF) and UV transmittance (T (UV-A) AV, T (UV-B) AV)
It is known from AS/NZS 4399:1996 that the UVF protection factor UPF (Ultraviolet Protection Factor) is the ability of a fabric to protect against UV rays. It is the ratio of the average amount of ultraviolet radiation to unprotected skin to the amount of ultraviolet radiation that is occluded by the fabric to be tested.
The UV radiation source provides sufficient and stable UV radiation energy for the test. The monochromator disperses the ultraviolet radiation energy of the radiation source for spectral measurements. The integrating sphere calculates the spectral radiant flux from all directions (direct and diffuse) emitted by the sample. The detector is composed of a photomultiplier tube. After the signal is amplified and processed, it is input into a computer for final processing of the signal.
3.2 Factors affecting the UV transmittance of textiles
The transmission of ultraviolet light depends on many factors, such as the structure of the tissue, the coverage factor, the color, the chemical additives in the processing and the handling of the sample:
1) Structure and structure of the fabric: The denser the woven or knitted fabric, the smaller the throughput of ultraviolet rays. The same fabric structure, the UV protection performance increases with the thickness and quality of the fabric, and basically depends on the coverage factor of the fabric.
2) Types of fabric fibers: Different materials have different UV absorption properties. Both cotton and viscose fabrics have high UV transmission. Bleached cotton fabrics have greater transmission. Wool fabrics and silk fabrics have a high absorption capacity of ultraviolet rays. Polyester has a high UV absorption capacity due to its aromatic ring structure. A material with a matting agent that absorbs ultraviolet light more easily. Nylon fibers are fairly easy to pass through UV radiation.
3) The color and color of the fabric: Many dyes absorb ultraviolet light. In general, deep colors have better protection properties. Black and dark blue have lower UV transmittance.
4) Finishing: After UV-resistant fabric, it will affect its UV resistance after repeated washing. Clothing that is not UV-finished will improve its UV resistance after shrinking
5) Moisture content: Dry clothes with dry clothes have a lower UV transmittance.
4 Conclusion
A comparison of the different test methods can be seen:
1) The test principle is basically the same. The wavelength of ultraviolet light is divided into three bands of UV-A, UV-B and UV-C, of ​​which UV-A and UV-B have the greatest influence on the human body. GB/T 17032 is the transmittance of UV-B band (main peak wavelength 297nm) AS/NZS4399, AATCC183, BS7914 is the UFF value or transmittance of UV-A and UV-B bands.
Note: * Although starting from 280 nm, there is no or very little UV light transmitted through the fabric in the range of 280-290 nm.
2) The four methods have different requirements for the temperature and humidity environment of the test, and the degree of influence of the difference on the results needs further study. The test sample is required to be a dry, non-twisted fabric that is not in intimate contact with the skin.
3) AS/NZS4399, AATCC183, and BS7914 should be tested according to factors such as color and organization when testing samples.
GB/T17032 is suitable for any fabric.
4) GB/T17032 and BS7914 test results are UV transmittance: AS/NZS 4399 and AATCC 183 measured average UPF value and T (UV-A)? AV, T (UV-B)? AV.
5) The UV transmittance of the fabric is related to the structure, structure, fiber type and color of the fabric.
Cotton Jacquard Velvet,Cotton Velvet Lambswool Fabric,Bedding Colors Can Be Dyed,Velveteen Fabric Linen Waterproof Fabric
CHANGZHOU CHAOYANG KNITTING CO.,LTD , https://www.cychaoyangknitting.com