What are the types of denim fabrics?

Denim is a garment that can be worn all year round, so how to distinguish different types of denim (denim fabrics): First of all, according to the thickness of denim, it is divided into 4.5an, 6an, 8an, 10an, 11an, 12an, 13.5an, 14.5an, etc. 4.5an is very thin and is often used to make summer women's vests, sleeveless shirts, etc., while 14.5an is very thick and can be used to make winter men's cotton-padded jackets. Most of the jeans we often wear range from 8an to 12an.

In terms of the types of denim fabrics, it can be divided into plain, twill, herringbone, interwoven, bamboo, dark, and flocked denim. In terms of composition, denim is divided into combed and carded, 100% cotton, elastic (Lycra), cotton and linen blended, and Tencel. At present, the most popular denim varieties at home and abroad are mainly ring-spun denim, warp and weft bamboo denim, super indigo dyed denim, overprint, multi-color denim, and weft stretch denim, etc.

Ring-spun denim

With the development and application of new process equipment such as high-speed ring spinning, large package, fine winding, and knotless yarn, the shortcomings of coarse yarn, such as short spinning length, low production efficiency, and many knots, have been solved. The situation in which the yarn used for denim is replaced by air-spun yarn is changing rapidly, and ring-spun yarn is likely to make a comeback. Because ring-spun denim is superior to air-spun yarn in some properties, such as feel, drape, tear strength, etc., and also because of people's psychological return to nature and the influence of the original development of denim style, the more important reason is that after the ring-spun denim clothing is washed and processed, the surface will present a hazy bamboo style, which meets the personalized needs of today's denim clothing. In addition, bamboo denim clothing is very popular in the market, and ring bamboo can spin shorter and denser bamboo, which also promotes the development momentum of ring denim.

Slub denim

When the design uses slub yarns with different yarn numbers, different slub thickness (compared with base yarn), slub length and pitch, and uses slub yarns in single warp or single weft direction and both warp and weft directions, and properly proportions and arranges with normal yarns of the same or different numbers, a variety of slub denim can be produced. After the garment is washed and processed, it can form a variety of hazy or clear striped style denim clothing, which is welcomed by the consumer group with personalized needs.

Early slub denim was almost all made of ring-spun slub yarn, because it can spin slub yarns with shorter length, smaller pitch and relatively higher density, which is easy to form a denser embellishment effect on the fabric surface, and the warp slub is the main one. With the development of market consumer demand, warp and weft bidirectional slub denim is currently popular, especially bidirectional slub denim products with weft elasticity, which are very popular in both domestic and foreign markets. As for some varieties, as long as the organization structure is well designed, a single variety of ring yarn can be used in the warp direction, and bamboo yarn with an appropriate proportion in the weft direction can also achieve the effect of bidirectional bamboo denim in warp and weft.

Weft stretch denim

The use of spandex stretch yarn has brought denim varieties to a new field, making denim clothing both close-fitting and comfortable. With bamboo or different colors, denim products are more adaptable to fashionable and personalized consumer needs, so there is great development potential. At present, most stretch denim fabrics are weft stretch, and the elastic elongation is generally 20% to 40%. The size of the elastic elongation depends on the organization design of the fabric. The smaller the warp and weft organization tightness on the loom, the greater the elasticity. On the contrary, under the condition of fixed warp organization tightness, the greater the weft elastic yarn tightness, the smaller the elasticity. When the weft tightness reaches a certain level, it may even lose elasticity.

In addition, the outstanding problem of finished stretch denim fabrics is that the weft shrinkage rate is too large, generally more than 10%, and some even as high as more than 20%. Unstable fabric width brings great difficulties to clothing production. The solution is to avoid excessive elasticity in product design, generally 20% to 30%, that is, to maintain a certain warp and weft organization tightness, and to increase the tension appropriately during pre-shrinking and finishing, so that the fabric width has a larger shrinkage, thereby obtaining a lower residual shrinkage rate in the weft direction of the finished fabric. Another solution is to heat-set the stretch denim after pre-shrinking and finishing, so as to obtain a more uniform fabric width and a more stable and lower weft shrinkage rate, which meets the requirements of clothing processing and production.

Special color denim

Because the clothing made of super indigo dyed or extra deep indigo dyed denim can obtain a special effect of rich and bright color after grinding and washing, it is widely welcomed by consumers. "Super indigo" dyed denim has two major characteristics: the dyeing depth is particularly deep and the grinding and washing color fastness is particularly good. The former refers to the amount of indigo dye dyed on the yarn per unit weight (generally expressed as the percentage of the dye to the dry weight of the yarn, referred to as the dyeing depth). For example, the indigo dyeing depth of conventional denim warp yarn is 1% to 3%, while the dyeing depth of "super indigo" needs to reach more than 4% to be called super indigo or extra deep indigo.

The latter refers to the fact that "super indigo" dyed denim clothes need to be repeatedly washed for more than 3 hours, and their color can still reach or exceed the color depth of conventional dyed denim before washing, and its color is much richer and brighter than conventional dyed denim. For the washing fastness of indigo dyed denim, its essence depends on the degree of dye penetration into the yarn, rather than the washing fastness of the dye itself (indigo wet grinding fastness is only level 1), that is, the better the degree of penetration, the better the washing fastness.

In the past, the so-called "indigo dyeing quick washing process" actually meant that during the yarn dyeing process, the indigo dye was deliberately made to penetrate the fiber very shallowly. In this way, when the denim clothing was washed and processed, the extremely thin layer of dye on the surface of the yarn was washed away, revealing more white yarn core, making the color fade quickly, thus achieving the effect of immediate fading after a short period of washing. The "super indigo" dyeing process is the opposite. It requires the dye to penetrate the core very well, so that the denim clothing can obtain a deep and bright color after washing and processing.

Since the dyeing depth of "super indigo" dyed denim products is more than 60% higher than that of conventional traditional denim dyeing, the indigo concentration of the dye solution will also increase exponentially, even reaching 3-4g/L, in order to obtain a deeper and thicker color. In this way, the viscosity of the dye solution increases, the fluidity becomes worse, and the penetration ability of the dye leuco body is affected, so that the washing color fastness of the denim is reduced, and the final depth requirement of clothing production cannot be met. Therefore, some enterprises adopt the design of increasing the dyeing depth again, so that the indigo concentration of the dyeing solution increases again, and the penetration performance becomes worse. This back and forth forms a vicious cycle, and still cannot meet the requirements of "super indigo" color. The higher the indigo concentration in the dyeing solution, the heavier the red light of the dyed object, the darker the color, and there is no "super indigo" effect.

Therefore, many manufacturers have or are preparing to transform the dyeing and pulping equipment to solve this problem by increasing the number of dyeing passes. For example, increasing the number of dyeing passes to 8 or even 10 passes will not only increase the investment cost and dyeing material consumption, increase the difficulty of operation, but also increase the pollution to the environment. The better way to solve this contradiction is to appropriately reduce the proportion of insurance powder or caustic soda, especially the control of the amount of caustic soda, so that the pH value of the dyeing solution is stable between 11 and 12, the dyeing rate is the highest and the color is stable, and at the same time, the dyeing tension of the warp yarn sheet is appropriately reduced, so as to obtain a better "super indigo" dyeing effect.

Colored denim

In order to increase the color and color change of indigo denim, various color-coded denim varieties are currently very popular. For example, indigo dyed sulfur black, indigo dyed sulfur grass green, sulfur black green, sulfur blue, etc., to meet the personalized needs of the market. At the same time, it also enables denim manufacturers to have new denim varieties with patented characteristics to improve market competitiveness. In this regard, it is necessary to control the concentration of the mother liquor as much as possible to prevent excessive overflow of the dye solution, which will cause waste of dyes and expand environmental pollution.

Colored (multi-color) denim

Mainly include bromine indigo (commonly known as emerald blue in the market) denim and sulphur black denim, as well as coffee, emerald green, gray, khaki, and sulphur blue denim with sulphur dyes, and a small amount of bright red, pink, and princess denim dyed with Nafto dyes or reactive dyes. Although the production batch is not large, the market demand is more urgent and often cannot meet the needs.

The main problem is that the color and shade are not stable enough, and the dyeing is not very important, which makes the clothing manufacturers dissatisfied. This is certainly related to the small production batch and too many colors, but it is also difficult to produce all kinds of colors by the dyeing and slurry combination machine, which consumes a lot of energy, has high costs, and is difficult to treat sewage, etc., which also have a certain impact. The solution is to minimize the number of colors when designing, use two colors as much as possible, and no more than three colors, or use other more stable dyes to replace them, so as to adapt to the production characteristics of the dyeing and slurry combination machine and obtain a more stable dyeing effect. The second is to use the production process route of large-capacity dyeing of yarn in the yarn-dyed factory and warping in sections to produce all kinds of denim.

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