The appearance retention of fabrics refers to certain evaluations of the surface morphology of fabrics. It is the ability of fabrics to maintain their appearance without causing unpleasant morphological changes during wearing, washing, and storage. It includes wrinkle resistance, drape, iron-free properties, pleat retention, pilling, snagging, rigidity and flexibility, and color fastness. In addition to the above-mentioned properties, the appearance retention of knitted fabrics also has special detachment, hemming and skew properties.
During the process of wearing and washing, fabrics will be repeatedly rubbed and undergo plastic bending deformation, forming Wrinkles are called the wrinkles of fabrics. The wrinkle resistance of fabrics refers to the ability of the fabric to return to its original state due to elasticity after the external force that causes fabric wrinkles is removed. Therefore, the wrinkle resistance of fabrics is also often called wrinkle recovery. Clothes made of highly wrinkled fabrics are prone to wrinkles during wear, causing the style and size of the garment to lose its aesthetics and fit due to wrinkles. At the same time, the wrinkles are prone to wear and tear, resulting in reduced performance of the garment.
1. Test method
(1) Vertical method specimen Is convex. As shown in Figure 1. During the test, the sample is folded vertically in half along the folding line 1, placed flat on the splint of the test bench, and then placed on the glass pressure plate. Then, add a certain pressure to the glass pressure plate, release the pressure after a certain period of time, remove the pressure plate, stand the test bench upright, and use the protractor on the instrument to read the distance between the two folded surfaces of the sample. The angle of opening is called the crease recovery angle. Usually, the recovery angle after a short time (such as 15s) is called the acute elastic crease recovery angle, and the recovery angle after a longer time (such as 5min) is called the slow elastic crease recovery angle.
Figure 1, folding line
(2) Horizontal method test The sample is in strip shape. During the test, sample 1 is folded horizontally and clamped in the sample clamp 2, and a certain pressure is added. After a certain time, the pressure is released, as shown in Figure 2(a). Then, as shown in Figure 2(b), insert the sample clamp with the sample into the spring clip 4 on the instrument dial 3, and let one end of the sample extend out of the sample clamp to become the hanging free end. In order to eliminate the influence of gravity, the dial must be continuously rotated during the recovery process of the sample to keep the free end of the suspended sample coincident with the center vertical baseline of the instrument. After a certain period of time, the sharp elastic crease recovery angle and the slow elastic crease recovery angle are read from the dial. Usually the fold recovery angle in both warp and weft directions on both sides of the fabric is used as an indicator. In addition, it can also be expressed by the crease recovery rate, which is the crease recovery angle of the fabric accounting for 180%. The calculation formula is as follows:
Where: R ——Crease recovery rate (%);
a——Crease recovery angle (.).
The current measurement method only reflects the crease recovery property of the fabric in a single direction and in a single shape. This is different from the multi-directional and complex wrinkles of fabrics in actual use. Overseas, testing instruments have been developed that can produce creases on samples that are similar to actual wear. During the test, the sample is processed by instruments to produce creases, and then the force is released. After being left for a certain period of time, the crease status is graded and judged by visual inspection compared with the standard sample, so that the test results are closer to actual wear.
Picture 2
2. Main factors affecting the wrinkle resistance of fabrics
(1) Fiber properties
l. Fiber geometry
The fiber geometry affects the bending properties of the fiber, thereby affecting the wrinkle resistance of the fabric. Among the fiber geometry, linear density has the greatest influence. The greater the linear density of the fiber, the better the crease recovery properties of the fabric. The longer the fiber length, the better the crease recovery of the fabric. The cross-sectional shape of the fiber will directly affect the tangential sliding resistance between the fiber and yarn after the external force is released. Therefore, it also has a certain relationship with the crease recovery of the fabric. The crease recovery properties of special-shaped chemical fiber fabrics are generally not as good as those of round chemical fiber fabrics, but the difference is not significant. In the same way, the longitudinal shape of the fiber will also affect the crease recovery of the fabric. The crease recovery of the chemical fiber fabric that is smooth in the longitudinal direction is better than that of the chemical fiber fabric that is rough in the longitudinal direction.
2. Fiber elasticity
Fiber elasticity is the main factor affecting the crease recovery of fabrics. The elastic recovery rate of the fiber is particularly large, and the crease recovery property of the fabric is also large. For example, the elastic recovery rate of polyester fiber is high, and the crease recovery property of its fabric is also good. The elastic recovery rate of wool fiber is large, and the proportion of slow elastic deformation is small, so wool fabric has good crease recovery property. After wool fabric is wrinkled, it can recover in a short time.
Wool fiber
3. Fiber surface friction properties
Fiber surface friction propertiesWhen the �� coefficient is moderate, the fabric crease recovery is better.
(2) Yarn structure
When the yarn twist is low, the fibers in the yarn are loose , under the action of external force, slippage easily occurs between fibers, and most of this slippage cannot be restored; when the twist is high, the fibers in the yarn are tightly bound, and after the external force causes slippage between the fibers, the fibers move relative to each other. The ability to recover is low, making it difficult to eliminate the creases formed on the fabric surface. Therefore, when the yarn twist is moderate, the crease recovery of the fabric is better.
(3) Fabric geometry
Fabric structure has a great influence on crease recovery. For fabrics with many interweaving points, after the external force is removed, the yarns in the fabric are not easy to move relative to each other and return to their original state. Therefore, the crease recovery of the fabric is poor. Therefore, the crease recovery of the satin group is better, and the twill weave is in the middle. The plain weave is poor. Among knitted fabrics, if the coil length is long, the tangential sliding resistance between yarns is small, and the fabric is prone to large wrinkles and deformation under the action of external forces, leaving wrinkles. As the warp and weft density increases, the tangential sliding resistance between yarns in the fabric increases. After the external force is removed, the yarns are not easy to move relative to each other, and the crease recovery of the fabric decreases. Thicker fabrics have better crease recovery.
(4) Finishing
The crease recovery of gray fabric is the crease recovery of finished product The basis of fabric properties, and the finishing of gray fabrics has a particularly great impact on the crease recovery properties of fabrics. For example, using resin finishing on cotton and viscose fabrics will greatly improve the crease recovery of the finished fabrics. </p
