Key points to note when testing textile fiber content

Fiber content testing is very important in various testing of textiles. Almost every batch of samples needs to be tested for ingredient content. The testing data is not only related to the costs of manufacturers and distributors, but also to the health of consumers. According to the requirements of GB/T 29862-2013 “Textiles – Labeling of Fiber Content”: “Each product should be attached with a fiber content label”, especially this item is a required inspection item in random inspections at all levels. However, errors exist in any inspection, especially inspection items that rely heavily on manual labor. Therefore, it is particularly important to improve the accuracy of detection data. Based on inspection experience, this article summarizes common missed detection situations in current textile fiber content testing to improve the accuracy of inspection data.

Misjudgments and missed detections caused by different types of fabrics

01 Denim fabric

Through research and analysis of nearly a hundred batches of denim fabric testing data, it was found that samples containing 1% to 2% (or even lower) regenerated cellulose fibers are currently most likely to be missed. After excluding the influence of the personnel’s experience and physical condition, it was analyzed that the reason for the missed inspection was related to the darker dyeing of the denim fabric itself and unclear observation under the microscope. However, through empirical analysis, the main reason is that the regenerated cellulose fiber itself has abnormal morphology. The longitudinal section of the regenerated cellulose fibers in these denim fabrics is often ribbon-shaped and transparent and shiny, rather than the ordinary viscose fiber form. And in some cases, not every fiber has this shape. Often only 3 to 4 or more fibers will have this kind of situation, which requires the inspector to be careful enough.

02Pure mercerized cotton fabric

The pure mercerized cotton fabrics currently on the market are more complex in composition, but there is little difference in overall appearance and feel. In recent years, lyocell fiber, flax fiber and mulberry silk fiber have been detected in similar fabrics. In most cases, the content of flax fiber and mulberry silk fiber is very low. In addition, mercerized cotton, lyocell and mulberry silk have similar shapes. It is easy to cause misjudgment and missed detection.

03 Fabrics with no difference in appearance and pattern

In order to increase strength and comfort, some garments are made of fabrics with different fibers in different locations. If these fabrics are in areas with obvious differences such as sleeves, body, cuffs, and collars, they will have little impact on the inspector; if they exist in the same area and there is no obvious difference in appearance, they will be easily missed. For example, the fiber composition of the upper and lower parts of the front piece of a knitted sweater is different; the fabric composition of two samples with the same jacquard pattern is different, etc. This requires inspectors to have a systematic understanding of the entire fabric before conducting inspections. Fabrics with no difference in appearance require multiple sampling points for inspection.

04 Bottom fiber fabric

For clothing made of fiber hem fabrics, special attention needs to be paid to low-content fibers and trace fibers. It is recommended to use dyeing methods to characterize the fabrics. This will not only accurately characterize the fiber components, but also have a general understanding of their content, which will facilitate subsequent Provide reference for quantitative dissolution and other tests.

05 Yarn-dyed jacquard fabric

For samples of yarn-dyed fabrics with irregular jacquard patterns, yarns of different colors should be inspected separately, and inspection data should be issued separately. Experience shows that if the composition of each color yarn is very different, the data obtained from the inspection of different parts will be very different, which will have a serious impact on the inspection results.

Errors caused by changes in fiber solubility of reagents

With the changes in textile materials and the improvement of spinning technology, the solubility of conventional fibers has also changed to a certain extent. However, most of the solubility test methods in relevant inspection standards were developed many years ago, and the accuracy of the inspection under the current situation will be affected. cause certain impact.

Due to improvements in spandex production processes and differences in raw materials, the solubility of different types of spandex varies greatly. When using DMF to dissolve spandex, some spandex is difficult to completely dissolve even after oscillating in a 95°C water bath for 1 hour. This requires inspectors to carefully observe the dissolved fibers. If abnormalities are found, other methods should be used for inspection. The splitting method should be preferred for spandex content inspection.

For some acetate fiber, lyocell, and mulberry silk multi-component samples, try to avoid using the sequential dissolution method, and it is better to use the splitting method or the method of splitting and then dissolving for testing. Tests have shown that alkaline sodium hypochlorite solution has solubility to some acetate fibers, and acetone may have solubility to some mulberry silk fibers, but the solubility needs to be verified by further tests.

For blended fabrics of dark-colored cotton and lyocell fibers, a formic acid/zinc chloride solution dissolution test is required. Experience shows that it is better to perform the test after fading in an alkaline environment. Based only on standard methods, it is difficult for Lyocell fiber to be completely dissolved, which will cause unnecessary repeated tests and extend the inspection cycle.

When dissolving wool and mulberry silk blended samples, the 75% sulfuric acid method was used. If the sample was shaken and dissolved according to the standard, it would be difficult to completely dissolve it. Experience shows that it is more reasonable to use vigorous shaking at room temperature for dissolution.

Misjudgment caused by new or unusual fibers

In recent years, new fibers and functional fibers have emerged one after another, such as seaweed fiber,Chitosan fiber, glass fiber and some special modified acrylic fibers, etc. However, the inspection standards corresponding to these fibers have either been released soon or are in the drafting stage. This places higher requirements on the technical level of inspectors. Therefore, the understanding of new fibers and the study of relevant literature should be strengthened.

The impact of preprocessing on quantitative results

Dark-colored fabrics generally need to be faded before conducting the formic acid/zinc chloride solution dissolution test; denim fabrics, due to their darker color, sometimes have a greater impact on the test results, also need to be faded; those with large pulp content and hard feel Gray fabrics generally require desizing before inspection. Composite fabrics are often used in windproof jeans, windproof jackets, etc. The outer and inner layers of fabric are generally adhered by adhesive glue. If no glue removal pretreatment is performed, the quantitative inspection results will be greatly affected.

Although GB/T 2910.1-2009 “Quantitative Chemical Analysis of Textiles Part 2: General Testing Principles” clearly states the chemical reagents and methods used for degumming or desizing, these non-fibrous substances are often difficult to confirm, and the removal methods used are generally based on inspection It is difficult to unify the selection of personnel and experience. Different reagents and methods used will have different removal effects, which will have more or less impact on the quantitative results. This requires inspectors to be good at summarizing experience, carefully observing the removal conditions of the processed samples, and noting them in the inspection report if necessary. Clarify the pre-processing situation to avoid unnecessary disputes and disputes. For samples containing non-fibrous substances that are extremely difficult to remove, try to communicate with the customer and only perform qualitative testing on the sample.

Conclusion

Textile fiber content inspection is an inspection project that mainly relies on manual labor. It is highly dependent on personnel experience and uses relatively few instruments and equipment. This requires relevant personnel to focus on summarizing experience in daily inspections and frequently consult new literature reports to minimize the probability of missed inspections and misjudgments, thereby minimizing the accident rate and avoiding unnecessary economic losses to customers.

Source of article: Shanghai Textile Technology, China Textile Joint Inspection (Suzhou)

Editor: Decon Nano