"Crepe" and "wrinkle" are the phenomena that often appear in textile weaving. They are in essence the expression of different irregular concave and convex phenomena on the surface of fabric. However, it is precisely because of this different degree of performance that people have different attitudes towards them. The former is a phenomenon that people pursue, while the latter is a phenomenon that is excluded and taboo in production.

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1. Appearance characteristics

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Crepe (wrinkle) phenomenon is the irregular uneven phenomenon on the surface of the fabric, when the uneven degree is relatively small, delicate and uniform performance, called "crepe" phenomenon, this phenomenon gives people a feeling of microwave in appearance, easy to be visual acceptance, especially when using this kind of fabric to make summer intimate clothing, can make the ordinary clothes and skin surface contact into point contact, Give a person a cool and comfortable feeling, so, this crepe phenomenon is the pursuit of people in production and life.

When these uneven performance degree is relatively large, relatively rough, and not uniform fine distribution, called "wrinkle" phenomenon. This phenomenon of cloth generally attributed to the weaving of defective goods, is to avoid in production and life.

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Two, crepe (wrinkle) mechanism

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Crepe (crepe) is caused by different internal stresses between the yarns that make up the fabric or in different parts of the same yarn, which leads to inconsistent shrinkage and distortion of the yarn, thus showing crepe (wrinkle) phenomenon on the surface of the fabric. The main mechanism is due to the stretching of the yarn, twisting (considering whether the twist stress is completely eliminated after the shape of the yarn), and extrusion between the yarns resulting in different internal stresses within the yarn. From another point of view, the buckling state of yarn in the fabric can be divided into ideal state and non-ideal state two conditions, when the yarn interleaved buckling state of the fabric is ideal, the surface of the fabric flat; The crepe phenomenon occurs when all the interleaved buckling states of the fabric are not ideal. When the yarn of the fabric shows the ideal buckling state and the non-ideal buckling state does not appear regularly, it shows the wrinkle phenomenon.

To eliminate the internal stress of the yarn there are two main means: one is to relax the yarn naturally, the internal stress gradually disappear naturally. The other is through the method of shaping, in a certain temperature, humidity conditions, under certain external conditions, so that the fiber macromolecules rearrange, so as to eliminate the internal stress of the yarn.

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Three, the acquisition of crepe phenomenon

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Because of its beautiful appearance and cool characteristics as summer fabric, crepe fabric is artificially pursued in production and life, and it can be obtained by reforming in all aspects of raw materials, production technology, organization and matching and finishing.

3.1 Differences in raw materials

For example, under the premise of the same cotton warp, cotton yarn and cotton spandex core-cored yarn are used alternately as weft yarn. In this way, under the same filling strength, weft yarn elongation is different. The elongation of the former is much smaller than that of the latter, so the fabric is formed The latter two kinds of weft have different degrees of retraction, and the difference in the degree of retraction causes the surface to appear crepe.

3.2 Weaving process

Crepe fabric is also often obtained through the weaving process, mainly by varying the tension of the warp or weft. By using two warp feed shaft for warp sending, and make two warp feed shaft interval alternate incoming heald, two warp shaft using different warp letting so as to control the tension of warp, so that the adjacent warp will produce different degrees of contraction after the fabric off the machine, so as to get crepe effect; Similarly, different filling forces can also be used. The two adjacent weft yarns use different filling forces, so that the weft yarn of the fabric will produce different degrees of contraction after getting off the machine, and achieve crepe effect.

3.3 Organization Design

In the process of production, people sum up all kinds of tissues that can produce crepe effect, and obtain crepe effect by matching and adjusting different tissues. This method is relatively simple, only need to put a little effort in the organization of collocation can be. Often used crepe tissue mainly has the following types.

3.3.1 Add crepe structure

This kind of crepe tissue is mainly based on the original tissue or changing tissue, and then according to the law of another kind of tissue to add tissue points to form crepe tissue. For example, the corresponding crepe effect can be obtained by adding tissue points (as shown in Figure 1) in accordance with the law of 5/2 weft satin texture on the basis of plain texture.

Figure 1. Crepe structure of plain weave after adding tissue points according to 5/2 weft satin weave

3.3.2 Crepe tissue by moving drawing

By matching the two different tissues. The warp (or weft) of one organization can be inserted between the warp (or weft) of another organization. The insertion may be made in a ratio of 1 to 1, or in some other arrangement. For example, the tissue diagram obtained by drawing 2/2 weighted and flat 1/2 right twill tissue in a 1:1 ratio is shown in Figure 2. The adjusted tissue is often used to process crepe tissue in daily production.

3.3.3 Crepe structure with the same structure

This method is to select a kind of organization, and then adjust the arrangement order of the warp or weft of the organization. Assuming that the original arrangement order of the warp (or weft) is 1, 2, 3, 4, 5, 6, 4, 1, can be adjusted to 2, 5, 3, 6, 4, 1. The resulting new tissue does not have lines that point in one direction, and the disordered orientation creates a crepe effect. FIG. 3 is the crepe tissue diagram obtained after warp adjustment based on the picture.

3.3.4 Rotary crepe fabric

Figure 2. Crepe structure drawing after 1/2 weight and 1/2 right twill at 1:1 shift

Figure 3. Crepe structure after adjusting the warp

The organization chart is formed by piecing together a simple organization after rotation of 90°,180°,270° and itself, but the collocation and arrangement of these four pairs of organization charts should conform to a certain order. The original image is placed in the lower left corner, the tissue image after 90° rotation is placed in the upper left corner, the tissue image after 180° rotation is placed in the upper right corner, and the tissue image after 270° rotation is placed in the lower right corner. In order to facilitate future weaving, the basic fabric selected by this method should be the fabric with similar warp and weft points and the number of circulating yarn is generally less than 6. FIG. 4(b) shows the crepe structure diagram obtained after rotation in FIG. 4(a).

FIG. 4 Structure diagram of rotary crepe

In addition, there are many ways to get crepe structure in actual production. In short, it is to break the law of normal organization, so that the grain trend cannot be consistent or the yarn shrinkage size difference, so as to achieve crepe effect, which will not be introduced here one by one.

3.4 Post-finishing

The use of this method is also more common, is through the finishing method to obtain crepe effect. That is, in the post-finishing process, advanced technology and equipment such as crepe finishing, hot rolling finishing and washing crepe finishing are used to get the final crepe effect.

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Four, silk unique crepe effect

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Due to the special structure of silk, it has its own unique wrinkling method in addition to the concentrated wrinkling method described above. Silk has two parts of silk element and sericin, and the general silk is not degummed, such silk yarn twist shape, and then after degumming treatment, twisted yarn, especially after strengthening the twist of yarn will produce a tendency to untwist, using this characteristic, silk fabric will be more easy to obtain crepe effect.

No twist or weak twist is used for warp silk (≤10 twist /cm), and for weft silk, two or more single wires are combined to strengthen twist (more than 20 twist per cm, generally 22 ~ 28 twist /cm). There are two kinds of left twist and right twist, and the fabric is woven alternately with two left twist and two right twist. The fabric is plain weave. When the fabric is refined, due to the interaction of the left and right torsion force, the silk surface has a wrinkle effect, called crepe de chine. Unidirectional crepe refers to warp silk without twist or low twist, while weft silk is made of strong twist in one direction. After refining the fabric, twisting force in one direction will be generated by the silk, so that the creasing of the fabric will increase and wrinkles will be obvious.

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V. Conclusion

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"Crepe" and "wrinkle" are two different phenomena. In daily life, we avoid "wrinkle" and pursue "crepe". We will try our best to control the difference of yarn properties to ensure the smoothness of woven fabric and avoid wrinkling. At the same time, it is also believed that the corresponding crepe effect can be obtained by taking certain measures in the aspects of material, process, organization and finishing, or by using the special properties of some special raw materials. In short, our daily production and life is always accompanied by the abandonment of "wrinkle" to "crepe" phenomenon.