As we all know, textiles still account for a considerable proportion of China's total foreign trade exports. In recent years, China has successively promulgated relevant technical standards for textile testing, clearly stipulating the testing methods and standards for harmful substances in textiles. However, due to the lack of fast and effective testing methods, the effectiveness of the implementation of the standards remains to be studied. This article systematically introduces several common harmful substances in China's export textiles, and discusses effective methods of harmful substances detection in response to the current problems encountered in textile testing, hoping to have guiding significance for the practice of textile safety testing.
1. Main harmful substances in textiles and their content standards
1.1 Formaldehyde content
Due to the hazards of formaldehyde to human health, the European Union, North America, including Japan, all have very strict regulations on its content. Among them, Japan stipulates that the formaldehyde content in its imported adult outerwear must be less than 300mg/kg; the formaldehyde content in adult underwear, pajamas and socks must be less than 75mg/kg; and the content of baby products is more stringent. It is 20mg/kg.
1.2 harmful heavy metal content
Common harmful heavy metals in textiles include lead, nickel, cadmium, copper, arsenic, mercury, cobalt and chromium. Regarding the content of heavy metals in textiles, the European Union imposed strict regulations on its imported textiles as early as the end of the last century. Any textiles with heavy metal content above 0.5mg/cm2, including accessories, zippers and buttons, are not allowed to circulate in the market. .
1.3 Organic matter content
In 2003, China promulgated the BG18401 "National Textile Safety Technical Specification", which included 23 aromatic amines in the list of prohibited textile chemicals, and revised it in 2006, increasing the types of prohibited aromatic amines from 23 to 24. Kind. The "Specifications" also specifically pointed out that there is currently no effective detection method for 4-aminoazobenzene.
Among EU countries, Germany is the first country to restrict harmful chemicals in its textiles. Germany's ban on toxic organic chemicals in textiles was promulgated in 1994, and it clearly included 20 carcinogenic aromatic amines and azo dyes that may produce these aromatic amines in the prohibited list. German law also prohibits the production and use of pentachlorophenol, and stipulates that the content of pentachlorophenol in textiles and clothing must be less than 5mg/kg.
Later, on the basis of German standards, the European Union issued a decree on the prohibition of the use of harmful chemicals in textiles in 1997, and included pesticides containing toxic metal compounds in the prohibition list of cotton cultivation.
2. The current international anti-textile market and textile safety testing
With the increasing trade disputes on a global scale, developed countries have continuously set up barriers to entry for textiles produced in developing countries through so-called "green barriers" in order to protect their country's precarious textile industry.
Under the current competitive environment, traditional textile quality management standards no longer meet the current international trade market’s requirements for textile quality.
In order to maintain the dominant market position of China's textiles in international trade, it is necessary to abandon the traditional quality control system based on printing and dyeing quality, fabric quality and fastness quality, and extend the content and scope of quality control to the ecological performance of products.
Whether it is for luxury brands in the high-end market or low-end mass-brand textiles, the requirements for ecological indicators are uniform and indispensable. With the continuous intensification of international textile competition today, it is believed that future restrictions on textile ecology and health standards will become the main indicators for measuring textile quality in the future, and the requirements for textile safety testing will gradually become stricter.
3. Commonly used chemical detection methods and improvement suggestions
3.1 Formaldehyde detection
Formaldehyde has a wide range of uses in the textile production process, especially the textile auxiliaries with formaldehyde as the reactant, which have stronger durability; while the fabrics treated with formaldehyde have better wrinkle resistance and shrink resistance. However, due to the adverse effects of formaldehyde on human health, the detection of formaldehyde content in textiles has become an important part of its safety testing. Generally speaking, the methods for detecting the content of formaldehyde in textiles mainly include the following.
3.1.1 Meteorological chromatography
The meteorological chromatographic method determines the formaldehyde content of textiles through the polarity determination of trace amounts of formaldehyde released. The traditional formaldehyde trace amount is determined by the acetylacetone colorimetric method. Due to the small current measurement range and cumbersome measurement procedures, it is difficult to adapt to the multi-batch, multi-variety textiles and the large fluctuation range of formaldehyde content in foreign trade. Features. After analyzing the chemical characteristics of formaldehyde, combined with long-term testing practical experience, we found that 2,4-dinitrophenylhydrazine (2,4-DNPH) was selected as the derivatizing agent, and cycloethane was selected as the extractant. The detection of formaldehyde residues not only greatly simplifies the detection steps and expands the linear detection range of the content, but also reduces the risk of the detection process due to the low toxicity of cycloethane, which can greatly improve the detection of trace formaldehyde in textiles. Scope and efficiency.
3.1.2 Water extraction method
water extraction method is currently the most widely used method in practice. It is operated according to the GB/T2912.1-1998 standard. The detection process is relatively simple and easy to master.
Practice shows that if the iodometry and PH titrator are selected, and the formaldehyde in textiles is detected in the early stage, it can not only improve the accuracy of formaldehyde detection, but also greatly improve the detection efficiency.
3.2 Detection of heavy metals
3.2.1 Atomic Spectrophotometry
At present, the flame atomic absorption method is the most widely used method for measuring the amount of heavy metal residues in textiles. The flame atomic absorption method can effectively and quickly detect more than 60 heavy metal elements that may remain in textiles.
Because the method has simple detection steps and a relatively wide detection range, it has a good detection effect for heavy metal residues contained in textiles.
In contrast, although the graphite furnace atomic absorption atomic method is more efficient for measurement, its detection range is relatively small, and it is easily affected by the external environment, which affects the accuracy of the measurement. For several common heavy metal elements, such as arsenic and mercury, the detection effect of this method is not ideal. It is recommended to use atomic fluorescence method for detection.
3.2.2 Inductively coupled plasma emission spectrometry
In terms of the current practice of heavy metal content detection in textiles, inductively coupled plasma emission spectroscopy, or ICP-AES for short, is one of the most effective methods. However, this method also has certain shortcomings. For example, the detection sensitivity of mercury content in textiles is slightly insufficient, and the mercury content in general textiles is relatively low. Therefore, when measuring it, it is difficult to use ICP-AES to meet the detection needs. . However, if it is used in combination with a cyanide generator, and the element to be measured is sent to the ICP in the form of mercury vapor and separated, it can reduce the interference of the matrix and enhance the enrichment effect, thereby reducing the analysis cost. The detection limit meets the standard for extractable trace amounts of mercury in textiles.
4. Summary
Judging from the current pattern of international textile trade competition, trade protection measures with the theme of protecting human and environmental health will intensify in the future. In the textile industry, new harmful textile dyes and harmful textile auxiliaries will continue to emerge, which will inevitably have a certain impact on China's textile industry.
China’s textile industry needs to look at this issue from the perspective of the entire textile industry, constantly emancipate the mind, update concepts, and introduce the concepts of green production and fine management into the textile production process to promote the green and health of China’s textile products. In order to enable the detection technology of China’s textiles and harmful chemicals in textiles to meet the needs of China’s textile trade, the majority of scientific and technological workers need to continuously accelerate the development of new technologies, collect and digest new international textile safety testing technologies in a timely manner, for the textile industry Continue to maintain a leading position in international trade services.
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