“Crepe” and “wrinkle” are phenomena that often occur in textile weaving. They are essentially different degrees of irregular unevenness on the surface of the fabric. However, it is precisely because of this difference in the degree of expression that people have different attitudes towards them. The former is a phenomenon that people pursue, while the latter is a phenomenon that is rejected and taboo in production.
1. Appearance characteristics
Crepe The (wrinkle) phenomenon is the irregular unevenness on the surface of the fabric. When the unevenness is relatively small and appears fine and uniform, it is called the “crepe” phenomenon. This phenomenon gives people a microwave feeling in appearance. , easy to be visually accepted, especially when using this kind of fabric to make summer close-fitting clothing, it can change the normal surface contact between clothes and skin into point contact, giving people a cool and comfortable feeling. Therefore, this crepe phenomenon is What people pursue in production and life.
When these unevennesses are relatively large, rough, and cannot be distributed evenly and finely, it is called a “wrinkle” phenomenon. Cloths with this phenomenon are generally attributed to defective products of weaving, which should be avoided in production and life.
2. Creping (wrinkling) mechanism
Creping ( The reason for wrinkles is that the yarns that make up the fabric have different internal stresses or different parts of the same yarn, which leads to inconsistent shrinkage and distortion of the yarns, thus showing wrinkles on the surface of the fabric. )Phenomenon. The main mechanism is caused by the different internal stresses generated inside the yarn due to the stretching and twisting of the yarn (consider whether the twisting stress is completely eliminated after it is set), and the extrusion between the yarns. From another perspective, the buckling state of the yarns in the fabric can be divided into two situations: ideal state and non-ideal state. When the interlaced buckling state of the yarns in the fabric is all ideal, the surface of the fabric appears smooth; When the interlaced buckling state is all non-ideal, it will show a crepe phenomenon; when the yarns of the fabric show an ideal buckling state and a non-ideal buckling state appear irregularly, it will show a wrinkle phenomenon.
There are two main ways to eliminate the internal stress of the yarn: one is to make the yarn relax naturally, and the internal stress gradually disappears naturally. The other is to rearrange the fiber macromolecules under certain temperature, humidity and external force conditions through shaping methods, thereby eliminating the internal stress of the yarn.
3. Obtaining the Crepe Phenomenon
Due to the beautiful appearance of crepe fabric and its cool characteristics as a summer fabric, people are producing In life, we artificially pursue this kind of fabric, and transform all aspects of raw materials, production processes, tissue matching and finishing to obtain this kind of fabric.
3.1 Differences in raw materials
Using the special properties of raw materials, mainly It uses the elasticity difference of raw materials to weave, mainly using weft yarns with different elasticities. For example, on the premise of the same cotton warp yarn, cotton yarn and cotton-covered spandex core-spun yarn are used alternately as weft yarns, so that under the same weft insertion intensity , the elongation degree of the weft yarn is different, the elongation of the former is much smaller than that of the latter, so the two different weft yarns have different degrees of retraction after forming the fabric. Due to this difference in the degree of retraction, the surface will show Crepe phenomenon.
3.2 Weaving process
The crepe fabric is also obtained through weaving process A method that people often use is mainly by changing the different tensions of warp or weft yarns. By using two let-off beams for let-off, and the warp yarns on the two let-off beams are alternately introduced into the healds at intervals, the two warp beams use different let-off amounts to control the tension of the warp yarns, so that after the fabric is off the machine Adjacent warp yarns will shrink to varying degrees, resulting in a crepe effect. In the same way, different weft insertion strengths can also be used. Two adjacent weft yarns use different weft insertion forces, so that the fabric weft yarns after unloading will produce different degrees of shrinkage. Shrink to achieve a crepe effect.
3.3 Organizational Design
In the production process, people summarize various A kind of tissue that can produce the crepe effect. The crepe effect can be obtained through the coordination and adjustment of different tissues. This method is relatively simple and only requires a little effort in organizational matching. The commonly used crepe structures mainly include the following types.
3.3.1 Add-on crepe weave
This kind of crepe weave is mainly based on the original weave or changed weave. , and then add tissue points according to the rules of another tissue to form a crepe tissue. For example, on the basis of plain weave, adding weave points according to the rules of 5/2 weft satin weave (as shown in Figure 1) can obtain the corresponding crepe weave effect.
Figure 1 Crepe weave diagram after adding weave points to plain weave according to 5/2 weft satin weave
3.3.2 Transfer drawing method of crepe tissue
By comparing two different tissues to coordinate with each other. The warp yarns (or weft yarns) of one weave can be inserted between the warp yarns (or weft yarns) of another weave. This kind of warp and weft yarn insertion can be inserted according to the ratio of 1:1, or according to other arrangement ratios. For example, the tissue diagram obtained by transferring 2/2 warped flat and 1/2 right twill tissue at a ratio of 1:1 is shown in Figure 2. The adjusted tissue is used in daily life.It is often used to process crepe tissue.
3.3.3 Organization with the same organizational sequencing method
This The method is to select a weave, and then adjust the order of the warp or weft of the weave. Suppose the original order of the warp (or weft) is 1, 2, 3, 4, 5, 6, it can be adjusted to 2, 5, 3 ,6,4,1. In this way, the new tissue obtained will not have lines pointing in one direction, and the chaotic direction trends form a crepe effect. Figure 3 is based on is the basic tissue and the crepe tissue diagram obtained after warp adjustment. 3.3.4 Rotating crepe weave
Figure 2 2/2 weight flat and 1/2 right twill weave diagram after transfer and drawing at 1:1
Figure 3Crepe weave diagram after adjusting the tissue warp yarn
A simple organization is pieced together with itself after being rotated by 90°, 180°, and 270° to form an organization chart. However, the arrangement of these four organization charts must comply with a certain order. The original image is placed in the lower left corner, the 90° rotated organization chart is placed in the upper left corner, the 180° rotated organization chart is placed in the upper right corner, and the 270° rotated organization chart is placed in the lower right corner. For the convenience of future weaving, the basic weave used in this method should be a weave with similar warp and weft points and the number of circulating yarns is generally less than 6. Figure 4(b) is a crepe tissue diagram obtained after rotating Figure 4(a).
Figure 4 Rotation method crepe tissue diagram
In addition, there are many ways to obtain it in actual production The method of crepe weaving, in short, is to break the rules of normal weaving, so that the grain direction cannot be consistent or the yarn shrinkage is different, thereby achieving the crepe effect. I will not introduce them one by one here.
This method is also commonly used. It is through post-finishing methods to obtain the crepe effect. That is, in the post-finishing process, advanced processes and equipment such as wrinkle finishing, hot rolling finishing, and washed crepe finishing are used to obtain the final crepe effect.
4. The unique crepe effect of silk
Due to the special structure of silk, in addition to the above In addition to the concentrated wrinkle method introduced, it also has its own unique wrinkle method. Silk consists of two parts: silk fibroin and sericin, and generally factory silk is not degummed. After such silk threads are twisted and shaped, they are then degummed. The twisted yarn, especially the strengthened twist, will There is a tendency to untwist. Using this characteristic, silk fabrics will more easily obtain the crepe effect.
The warp yarn is made of untwisted or weakly twisted yarn (≤10 twist/cm), and the weft yarn is combined with two or more monofilaments to strengthen the twist (more than 20 twists per cm, generally 22~ 28 twist/cm). It is divided into two types: left-twisted and right-twisted, and two left-twisted silks and two right-twisted silks are alternately woven in. The fabric structure is plain weave. Once the fabric is refined, due to the interaction of the left and right torsional forces of the silk threads, the silk surface has a wrinkled effect, which is called crepe de chine. In smooth crepe, the warp threads are not twisted or low-twisted, and the weft threads are strongly twisted in the same direction. After the fabric is refined, the threads generate a torsional force in one direction, which increases the wrinkles of the fabric and makes the wrinkles obvious.
“Crepe” and “wrinkle” are Two different phenomena. In daily life, we avoid “wrinkles” and pursue “crepe”. We will try our best to control the difference in yarn properties to ensure the smoothness of the woven fabric and avoid wrinkles. At the same time, it is also believed that the corresponding crepe effect can be obtained by taking certain measures in materials, processes, organization, finishing, etc. or by utilizing the special properties of some special raw materials. In short, our daily production and life are always accompanied by the phenomenon of abandoning “wrinkles” and seeking “crepe”. </p