Causes of fabric creases and anti-wrinkle principles

The anti-wrinkle finish of cotton fabric for a long time mainly uses aldehyde-amine condensation resin, especially thermosetting N-light methyl resin or N-light methyl resin Phthalamine compounds, such as dimethyldihydroxyethylene (DMDHEu, 2D resin for short), trihydroxymethylmelamine (TMM) resin, etc., of which ZD resin is the most widely used. ZD resin has 4 chain groups, and the properties of the light groups in different positions are different, so their reactivity is also different. The active N-hydroxymethyl groups and cellulose fibers are cross-linked to give the fabric better anti-wrinkle effect. The reaction between ZD resin and cellulose mainly takes place on the primary hydroxyl group.

In an acidic medium, the proton combines with the unshared electron pair of the oxygen atom in the hydroxyl compound to form a transition state product of the oxygen ion, and then it desorbs One moleculeµl of water is removed and the next carbon ion reacts with the light group of cellulose to obtain the etherification product of cellulose. Wrinkles on the fabric, from a microscopic point of view, are mainly due to the deformation of the fibers under the influence of external force. After the external force is removed, the deformation cannot disappear and the original shape cannot be restored or only partially restored. When the fiber is subjected to an external force, the molecular chains are neatly arranged in the crystal region with great regularity, more hydrogen bonds are formed and they can jointly carry the external force. Therefore, under the influence of an external force not exceeding the elastic limit, only a small reversible deformation generally occurs, that is, ordinary elastic deformation. In the low-regularity amorphous region, most of the warp groups are in a free statend and few hydrogen bonds are formed. When exposed to external force during washing or wearing, the cellulose molecules are deformed in the direction of the external force. The base structure The unit slides relative to each other and the base will generate new hydrogen bonds at the new position to fix the deformation. When the external force is removed, the system will recover from creep. If the resistance generated by the newly formed hydrogen bonds is greater than the restoring force, the deformation will be fixed. When the deformation of the system cannot be recovered, permanent deformation occurs. A variety of morphological changes are produced due to the diversity of hydrogen bonds, and the performance of this non-uniform and irreversible deformation is the wrinkling of the fabric.

To overcome the shortcoming that cotton is easilycreases, it is necessary to reduce the probability of relative displacement between macromolecules under the influence of external force, or when the relative displacement of macromolecules It may hinder the formation of hydrogen bonds at new positions, so that after the external force is removed, the macromolecules quickly return to their original positions. Introducing a certain amount of chemical bonds (covalent cross-linking) between the macromolecular chain of cellulose and the basic structural unit can prevent the relative displacement between the basic structural units of the fiber and improve the elastic recovery of the cellulose fiber. ripple resistance.

Cotton fiber is a post-D glucose residue base that is passed throughIt is composed of fiber macromolecules linked by 1,4 common bonds. There are three free radicals that can form hydrogen bonds on each glucose cellng in the cellulose molecule and all have the chemical characteristics of common alcoholic hydroxyl groups. On the glucose end group on the right side of the molecular chain, due to the tautomerism of the oxygen ring type and the open chain type, there is a potential aldehyde group, so the cellulose also reduces. However, compared with the relative molecular weight of cellulose, the number of aldehyde groups is too small, so the reducibility is not significant, but when the cellulose is damaged or destroyed and the relative molecular weight decreases, the reducibility will gradually become apparent.

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