In the 1960s, polyurethane resin was used for anti-wrinkle finishing of textiles in foreign countries. The polyurethane resin used was basically solvent and emulsion, with disadvantages such as not easy to emulsify, poor stability and toxicity.In the 1970s, waterborne polyurethane resin was gradually applied.As an anti-wrinkle finishing agent, WPU can obviously improve the resilience, abrasion resistance and fabric strength of the fabric.Natural fiber fabric, especially cotton fiber, has the advantages of natural feel, moisture absorption, antistatic, comfortable to wear and economic benefits.But pure cotton fabric also has the disadvantage of poor elasticity, easy wrinkling and ironing after washing.In recent years, people advocate nature, and cotton fiber fabric is popular, and with the improvement of people's living standards and the acceleration of the pace of life, people are not only comfortable to wear clothing requirements, to maintain smooth appearance, cooking simple also put forward higher requirements.Therefore, anti - wrinkle and durable pressing finishing once again become a research focus

Cotton fiber in the amorphous area of the neat degree is low, most of the hydroxyl in the free state, the formation of hydrogen bonds is less, in the process of washing or wear through external force, the cellulose molecules certain deformation along the direction of the external force, the basic structure unit, relative slip will produce hydroxyl in the new position and new hydrogen bond rearrangement.When the external force is removed, the system will creep back, and if the resistance generated by the newly formed hydrogen bond is greater than the restoring force, the deformation of the system cannot be restored, then permanent deformation will occur.Due to the diversity of hydrogen bond arrangement, there are many morphological changes. The macroscopic manifestation of this uneven and irreversible deformation is the crease of the fabric.In addition, the area of cross section of cotton fiber increases by more than 40% when it is swollen in water, but its length does not change much. Because of the interlacing of warp and weft yarn, it shows uneven shrinkage and uneven recovery when dry, which is also one of the reasons for fold formation.Cellulose is usually cross-linked with an anti - wrinkle finishing agent (waterborne polyurethane) under high temperature baking.Dry fibers are tightly cross-linked, so not only do dry textiles have wrinkle resistance (also known as dry wrinkle resistance), but also the fiber will swell in water and be cross-linked and will not produce wrinkles, that is, it also has wet wrinkle resistance.

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