Research On The Detection Of Fiber Content In Knitted Thermal Underwear

　　 The fiber content of knitted thermal underwear is an important index for its quality assessment. fibre The variety and content of the product directly affect the performance and sales price of the whole underwear, so both the business and the consumers are very concerned about it. But manufacturers often find that there are some differences between the initial design of knitted thermal underwear and the fiber content detected by textile testing organizations. Knitted thermal underwear The related problems in fiber content detection were analyzed.

　　 One Spandex Products Quantitative analysis of deviations

Spandex is widely used in thermal underwear. It can give thermal underwear better wearability and comfort, and achieve the integration of body shaping and warmth retention functions. In the process of testing the thermal underwear with spandex, the content of spandex measured by different detection methods is quite different, resulting in disputes.

The methods commonly used for testing the fiber content of spandex products are splitting and chemical methods.

There are different degrees of deviation between the spandex content obtained by the two methods and the true value of spandex. The size of the deviation depends on the content of non fibrous substances. Therefore, in the detection of Spandex Products, the accuracy of testing can be greatly improved if the non fiber material can be removed. But in actual detection, we usually do not pretreat samples. Therefore, the content of spandex obtained from the same spandex product is different by the method of splitting and chemical dissolution. The content of spandex obtained by general chemical dissolution is higher than that obtained by the method of splitting. This is because the content of spandex in chemical dissolution includes the content of non fiber material. But for coated spandex products, the content of non fibrous substances is also changed because of the different solubility of the coating in chemical reagents. At this time, the content of spandex, the method of separation and the content of spandex in chemical solution are not fixed. Or remove the coating and then detect the content of spandex so that the accuracy of the test can be improved.

2 the problem of split and lamination of knitted thermal underwear

At present, the knitted thermal underwear made in Jiangyin is made of three layers of thermal insulation. However, due to the post-processing procedures such as dyeing and finishing, some of the thermal underwear can not be split into three layers according to the original weaving process for content detection. The main reason is that after the dyeing and finishing process, the performance of spandex has changed, and it can not be separated by sticking together, so that the middle layer and the inner layer can not be separated, and there is no way to split the three layers. In such a situation, it is only possible to split the grey cloth that has not been dyeing and finishing, so as to carry out three levels of detection.

3 loss of fiber content

With the development of science and technology, the raw materials of knitted thermal underwear are becoming more and more abundant. Functional fibers are constantly applied to thermal underwear, giving them comfort, warmth, breathability, antibacterial and health care functions. However, due to the variety of new fibers, subsequent dyeing and finishing technology can not reach the best matching degree with each fiber, which makes the functional fiber content of the finished thermal underwear less, and fails to achieve the expected design targets. In order to achieve the original design value, fiber loss must be taken into account when feeding, so that the fiber content of finished underwear meets the design requirements. But this makes the production cost of knitted thermal underwear increased. In order to solve these problems, it is urgent to improve the dyeing and finishing technology of knitted thermal underwear, and reduce fiber loss as far as possible.

The content of wool knitted thermal underwear is taken as an example. The surface fiber is cotton and the middle layer fiber is wool and polyester blended yarn. The yarn ratio is 10/90 while the inner layer fiber is polyester. The contents of the finished products are: cotton on the surface, 5% in the middle layer, 94% in polyester, and polyester in the inner layer. It can be seen that the content of the middle layer of the knitted thermal underwear from the design to the finished product has changed greatly, and the difference between the design value and the detection value of the fiber content is analyzed from weaving and dyeing and finishing processes.

1) loss of fiber content during weaving stage

In the weaving process of knitted thermal underwear, the yarn loses its surface due to its own friction and the high-speed weaving process of the circular knitting machine. The yarn loss is different due to the different twist strength of different yarns. In this case, the surface is full cotton yarn. Since it is a single component, it remains the same as cotton after its loss. However, due to the different properties of wool and polyester fiber, the loss of wool polyester yarn in the middle layer will also be different in the weaving process, and the proportion of wool polyester 10/90 will change. Because wool fibers are natural fibers with poor uniformity and longer length, they are more likely to fall off the surface of yarns than polyester fibers. After weaving process, the loss of wool and cashmere is more, and the proportion of polyester fiber will increase. The whole polyester yarn in the inner layer is a single component, so the proportion of the polyester yarn is constant after loss.

2) loss of fiber content caused by dyeing and finishing

After weaving, we need dyeing and finishing to obtain the color and feel we need. The light colored knitted thermal underwear needs to be treated by half bleaching. The loss of the treated fiber is even larger than that of the dark color, and the semi bleaching treatment is carried out in alkaline environment, and the damage to the wool fiber is the largest. The fiber loss in this case is mainly shown on wool fibers. The surface and inner layer will lose weight only in the dyeing and finishing process because of the single component raw materials, and the proportion will not change.

In this case, the underwear of the three layers of underwear is different from each other. The surface cotton is alkali resistant and acid proof. The middle layer is acid resistant and alkali resistant. The polyester fiber is acid resistant and alkaline. Therefore, it is difficult to take into account that the dye is dyed and dyed to the three. In order to reduce damage, three layers of yarns can be dyed and knitted, but the color difference is easy to appear and the process is long. Although we have used many new reactive dyes, there are varying degrees of damage to all kinds of fibers. In general, the dyes used in dyeing process tend to be the main components, so the wool fibers in this case will suffer more damage. Enterprises can take measures to add wool protectant to reduce fiber loss. Through a large number of experiments, it can be seen that adding wool protectant can generally reduce the loss of wool fiber by about 2%.

According to the above analysis, the wool fiber in the middle layer of the thermal underwear produced a great loss in weaving and dyeing and finishing. The content of wool in the final test is about 5%. If wool protector is added, the wool content can be increased to about 7%. As the surface and inner layers are all single components, the fiber weight varies but the proportion remains unchanged.

4 Conclusion

　　 To sum up, the difference in thermal underwear content is the largest proportion of fibers in multi component yarns. The three layers of raw materials of knitted thermal underwear are different. In general, the middle layer changes the most. We should pay more attention to the loss of those fibers with many components and low contents, because the new fibers added to the thermal underwear are mostly functional fibers and the price is more expensive, and the proportion of the commonly added fibers is less. If the fiber loss is greater in the post dyeing process, the content of the functional fiber will be reduced a lot. Therefore, improving dyeing and finishing technology and testing technology of knitted thermal underwear is an important way to solve the differences.