Author: Cui Qinghua Yang Xiaoyong Gao Shun Ying
Abstract: The relevant precautions in the process of fiber qualitative analysis and detection were analyzed and discussed, and the author's insights were put forward.
Key words: fiber; qualitative analysis; precautions
Abstract: In this paper, the notes on the operation details of the qualitative analysis of the fibers were discussed, and author's views were put forward.
Keywords: Fibers; Qualitative Analysis; Notes
The detection of fiber content is roughly divided into two parts. Usually, the first step is to perform qualitative fiber analysis and then perform quantitative fiber analysis. Except for one component, qualitative analysis does not require quantitative analysis when it is determined that the fiber product has only one fiber composition. It can be considered that the content of such fibers is 100%. However, extra care is required because often the product contains traces of other fibers. The qualitative analysis of the fiber is inaccurate, and the following situations will occur: First, the second step of quantitative analysis cannot be carried out: if the product is blended with cotton and acrylic fiber, it is qualitatively mixed with cotton and nylon. Because the reagents used are different, the test cannot be carried out, that is, The test results are also wrong. In another case, the content of a certain fiber is relatively small, and it is not found when qualitative, and the result is also wrong. Therefore, qualitative is the top priority in fiber content detection.
1 Standards and methods for fiber characterization Currently, there are many domestic standards for the qualitative use of fibers. In addition, there are qualitative methods for new fibers in SN/T related standards.
The daily use is more FZ/T01057.1-4 and GB/T 16988. The above various methods are designed according to the physical and chemical properties of the fiber. The standard FZ/T01057.1 specifies some common technical requirements for textile fiber identification test methods, and gives a general procedure for fiber identification tests. FZ/T01057.2 is based on the odor and the state of the residue when the fiber is burned. FZ/T01057.3 is distinguished by the appearance of the fiber, including the longitudinal and transverse forms. FZ / T01057.4 is distinguished by the solubility of the fibers in different solutions. FZ/T01057.5 is distinguished by the dyeability of the fiber. FZ/T01057.6 is distinguished by the difference in melting point of different fibers. For example, nylon 6 and nylon 66 have the same odor and residue state when ignited, and the solubility is basically the same in the same solution. The longitudinal shape is observed under a microscope, and the above methods cannot be used to separate them. The melting points of the fibers are inconsistent, nylon 6 is 215 to 224 ° C, and nylon 66 is 250 to 258 ° C. FZ/T 01057.7 is distinguished by the difference in density of the different fibers. The GB/T16988 standard gives the longitudinal morphology of various wool fibers, which are distinguished by observing the size, thickness, density, and uniformity of the scales under the microscope. When you use the standard according to the standard, you can judge the specific phenomenon of each fiber according to the different methods described in the standard.
In addition to the above standard methods, there is also an unconventional fiber qualitative method, which is a hand-feeling method. The visual method of hand touch is to touch the hand, observe the eye, and judge the type of fiber by experience. This method is simple and does not require any instruments, but requires extensive experience from the identification personnel. When the fabric is identified, in addition to touching and observing the fabric, the yarn can be removed from the edge of the fabric for identification.
The visual characteristics of common fibers are summarized as follows:
(1) Feel and strength Cotton and hemp are harder, wool is soft, and silk, viscose and nylon are moderate. When broken by hand, silk, hemp, cotton, and synthetic fibers are strong; hair, viscose, and acetate fibers are weak.
(2) Elongation When stretching fibers, the elongation of cotton and hemp is small; the elongation of wool and acetate fibers is large; the elongation of silk, viscose and most synthetic fibers is moderate.
(3) Length and uniformity The length and uniformity of natural fibers are poor, and the length and uniformity of chemical fibers are good. Cotton fibers are soft and soft and have a short length. The wool is long and curly, soft and elastic. The silk is long and slender and has a special luster. Hemp fiber is gelatinous and hard.
(4) Weight Cotton, hemp and viscose fiber are heavier than silk; nylon, acrylic and polypropylene are lighter than silk; wool, polyester, vinylon and acetate are similar in weight to silk.
The visual inspection method is extremely demanding on the tester, unless very experienced by very experienced operators, but for laboratory testing, if you master the basic feel of some common fibers, it is bound to be our daily inspection work. Come for a certain help.
2 General procedure for fiber characterization Qualitative analysis is based on the separation of fibers based on the physical and chemical properties of the fibers.
In the FZ/T 01057.1-2007 standard, the fibers to be tested are roughly classified by microscopy, and natural cellulose fibers (such as cotton and hemp), regenerated cellulose fibers (such as viscose, etc.), and animal fibers are separated. Such as wool, cashmere, rabbit hair, camel hair, alpaca hair, mohair, yak wool, silk, etc.), chemical fiber. The second step of chemical fiber, including rayon, is further confirmed by one or several methods such as combustion method and dissolution method to finally determine the type of fiber to be tested.
However, in the actual inspection process, it is possible to follow the individual's habits without having to limit the standard procedures. If you use the combustion method first, then use the microscope method, the dissolution method, etc. As long as the different fibers can be correctly identified.
(1) If it is an unknown sample, it is generally identified by the following procedure.
The first step: stretching If you can stretch more than 2 times, put concentrated sulfuric acid: dissolve (spandex); do not dissolve (rubber); if not stretch more than 2 times (go into the second step);
The second step: microscopic projection unique shape: longitudinal distortion, transverse waist-shaped cavity: cotton; longitudinal section, transverse waist-shaped cavity: hemp; longitudinal groove, lateral zigzag: viscose; longitudinal scales, lateral approximation Shape: wool; other (into the third step);
The third step: 70% sulfuric acid, such as dissolution, re-burning: hair burning (silk); paper burning (other regenerated cellulose fibers); if not dissolved (go to the fourth step);
The fourth step: 36% ~ 38% hydrochloric acid, such as dissolved (for nylon): 15% hydrochloric acid can be used again, dissolved (nylon 6), insoluble (nylon 66); if not dissolved (go into the fifth step)
The fifth step: 65% ~ 68% nitric acid, such as dissolved (is acrylic); if not dissolved (go to the sixth step);
Step 6: 40% sodium hydroxide, such as dissolved (for polyester); if not dissolved (for polypropylene).
(2) If it can be determined at the outset that the sample composition is all chemical fibers, further identification can be performed according to the procedure shown in FIG.
Figure 1 Chemical fiber identification flow chart Of course, any identification procedure is not suitable for all situations, there must be one or the other defects, which requires the operator to flexibly choose during the experiment to ensure the accuracy of the test results to the greatest extent.
3 Problems in the process of qualitative analysis In recent years, with the improvement of the performance requirements of fiber products, the popular fabrics at home and abroad have adopted a large number of Tecel, Modal, Viloft, bamboo pulp fiber and bamboo originals with comfort and environmental protection. Fiber, soy protein fiber, chitin fiber, etc., the development and application of these new textile fibers meet the green consumer demand. However, at present, some products have appeared in the market, and the accurate recognition and identification of these new fibers has become an important topic in the field of textile testing. At present, the following problems mainly exist in the qualitative analysis of fibers:
(1) Because there is no clear name in many new fiber standards, the name of the fiber marked in the product does not have a corresponding name in the standard when it is qualitative, and it is inconsistent with the product label when the report is issued. For example, many commodity labels on the market are marked with bamboo fiber. Although the figure of bamboo fiber is attached in FZ/T01057.3-2007, there is no language description. In FZ/T0105.3-2007, in Appendix C, the name of the supplementary fiber. Only the names of bamboo (original) fibers and bamboo pulp fibers are given for reference, and no specific labeling is given. Therefore, in this case, most manufacturers can not provide the production process certification of the fiber, so most laboratories label the bamboo pulp fiber as a new type of regenerated cellulose fiber.
(2) In the production process, the shape of the spinning holes is different, resulting in different appearances of the fibers. Even in the same spinning solution, fibers having completely different cross-sectional shapes and longitudinal shapes can be spun. If the longitudinal and cross-sectional shapes of the unknown fiber are observed under a microscope according to the standard FZ/T01057.3-2007 "Textile fiber identification test method Part 3: Microscopy", the standard photo and morphological description of the control fiber are used to identify the unknown fiber type. It may not be possible to judge the type of fiber. For example, there are many kinds of modal fibers, including modal fibers made in Taiwan, lyon modal fibers from Austria, Newdale fibers and other modal fibers. These modal fibers are all regenerated cellulose fibers, and they are called "modal fibers or new generations." Fiber." Although they belong to Modal regenerated cellulose fibers, their longitudinal shape characteristics are different from each other. There are some grooves in the appearance, some are not. Even if there are grooves and the groove shape, size and number of grooves are different, Even the same type of modal fiber may have different appearances due to changes in environmental conditions (such as changes in air flow speed) after the spinning solution exits the spinning hole, and each type of modal fiber and textile fiber Identification test methods - Part 3: Cross-section, longitudinal morphological characterization of the modal fibres listed in Appendix B of the Microscopy (FZ/T01057.3-2007) and cross-sections and longitudinals of the modal fibres listed in Appendix C Morphological micrographs are inconsistent or incomplete. It can be seen that with the continuous emergence of new fibers, it is no longer feasible to rely on a certain means or method to identify fibers. For fiber characterization, especially the characterization of new fibers, a variety of means or methods should be used to comprehensively determine in order to obtain accurate qualitative results.
(3) The formulation and revision of standards seriously lags behind the introduction speed of new fibers on the market. At present, most of the standards we use in fiber characterization are before 2007, and many new fibers appear after standard setting. Therefore, many new fibers are not involved in many standards, which requires our national departments to set up special Structure, timely understanding of market dynamics, organization of relevant experts and scholars to develop or modify relevant standards. On the one hand, it can better regulate the production and market order of enterprises, on the other hand, it can also improve the position of Chinese enterprises in the world textile market.
(4) The distribution of textile enterprises in China is not balanced, and some types of fibers are relatively concentrated in production. Therefore, some laboratories or testing institutions routinely test only some types of fibers, but for other fibers, especially some new fibers. Relatively insufficient understanding. Especially in the era of this new type of fiber, this is even more difficult to adapt to the needs of the market. In response to this situation, our relevant departments should regularly organize relevant training or exchange activities, so that everyone has a platform for mutual learning and learning, and also helps to improve the strength of our country's textile testing.
4 Qualitative analysis should pay attention to the problem (1) must pay attention to the integrity of the sampling, must include all the fibers in the product when sampling, so as not to miss.
(2) When a method cannot be completely determined, several methods should be used to ensure the accuracy of the results as much as possible.
(3) Constantly accumulate fiber related new knowledge and enrich your own experience. For fiber qualitative, experience is the most important.
5 Qualitative analysis of the operator's requirements In order to do a good job in fiber characterization, the author believes that the operator needs to do the following:
(1) Personnel engaged in qualitative analysis of fibers should have basic knowledge of various fibers, especially to grasp the physical properties of fibers such as fiber morphology including longitudinal and transverse morphology, color, fineness, etc. and chemical properties of fibers such as solubility properties, Combustion performance, heat resistance, etc., this is the most basic knowledge of the separation of fibers. With the increase of new and modified fibers, each person must constantly learn new knowledge and enrich himself.
(2) Personnel engaged in qualitative analysis of fibers should have a strong sense of responsibility and be meticulous in their work and must not fool things. If the fiber content is clearly indicated on the sample or sample, the person who has tested the fiber content knows that this data (including the composition) is often inaccurate and the reliability is poor. If the qualitative analysis is not carried out, the ingredients are directly tested. Will produce the wrong result.
In addition to the above two conditions, there must be a scientific method. The so-called scientific method is to continuously accumulate experience, use standards flexibly, and use different methods to save time and effort and achieve accurate judgment.
In short, good fiber characterization is the top priority in the fiber content testing process. It is important to cause the operator to pay sufficient attention to each operation detail to ensure the detection results are as accurate as possible.
references:
[1] FZ/T01057.1-2007 "Textile fiber identification test method Part 1: General description" [S].
[2] FZ/T01057.2-2007 "Textile fiber identification test method Part 2: Combustion method" [S].
[3] FZ/T01057.3-2007 "Textile fiber identification test method Part 3: Microscopy" [S].
[4] FZ/T01057.4-2007 "Textile fiber identification test method Part 4: Dissolution method" [S].
[5] FZ/T01057.5-2007 "Textile fiber identification test method - Part 5: Chloride and nitrogen-containing color reaction method" [S].
[6] FZ/T01057.6-2007 "Textile fiber identification test method Part 6: Melting point method" [S].
[7] FZ/T01057.7-2007 "Textile fiber identification test method Part 7: Density gradient method" [S].
[8] FZ/T01057.8-2007 "Textile fiber identification test method Part 8: Infrared spectroscopy" [S].
[9] FZ/T01057.9-2007 "Textile fiber identification test method Part 9: Birefringence method" [S].
[10] GB/T16988-1997 "Determination of the content of special animal fiber and sheep wool mixture" [S].
[11] SN/T 1690.1-2005 "New textile fiber composition analysis method Part 1: Soy protein fiber" [S].
[12] SN/T 1524-2005 "Method for the Identification of Aromatic Polyamide Fibers" [S].
[13] SN/T 1567-2005 "Modal fiber / acrylic fiber blended product and milk fiber composition analysis method" [S].
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