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1 Concept 1.1 What is a color-changing fiber?
The so-called color-changing fiber is a fiber having a special composition or structure that can automatically change color after being stimulated by external conditions such as light, heat, moisture or radiation. The main varieties of color-changing fibers are photochromic and thermochromic. The former means that certain substances can produce discoloration under the illumination of a certain wavelength of light, and under the irradiation of another wavelength of light (or heat), reversible changes will return to the original color; the latter refers to By attaching special microcapsules to the surface of the fabric, the microcapsules can be used to change color with temperature, and the fibers produce corresponding color changes, and this change is also reversible.
The variety of color-changing fibers is mainly concentrated on photochromism. In fact, as early as 1989, W. For the first time, MARCKWALD has found that certain solid or liquid compounds have photochromic properties. The materials with photochromic properties are usually organic compounds with isomers such as naphthopyran, spirooxazine and norbornene derivatives. These chemicals undergo a change in the bonding mode or electronic state corresponding to the two compounds due to the action of light, and reversible color development, discoloration, and discoloration can occur in two states in which the absorption spectra are different.
The earliest application example was a fabric developed by CYANAMIDE in the United States to meet the requirements of the US military for combat clothing during the Vietnam War. However, Donghua University in China uses light yellow-green trimethylspiropyrazine as a photosensitizer, which is also blended with polypropylene chips to form a photosensitive fiber formed by high-temperature melt spinning. The fiber can be rapidly changed from colorless to blue after being irradiated with ultraviolet rays, and can be quickly changed to colorless after the light is stopped, and has good washing durability and a certain light durability. The corresponding products are also photosensitive color-changing fabrics of KANEBO Corporation of Japan, and T-shirts made of such fabrics were supplied to the market as early as 1989. Several universities, such as CLEMSON University and GEOR-GIA Polytechnic Institute in the United States, have recently begun to study the surface coating materials that change the photosensitive fibers, so that the color of the fibers can be automatically controlled. In the civilian sector, photosensitive color-changing fibers are mainly used in entertainment clothing, safety clothing and accessories, and anti-counterfeiting labels.
Also, a general color-changing material refers to a material having photochromic properties such as light, heat, electricity, and the like. In particular, the wings of the glittering color-changing fiber butterfly and the feathers of the peacock are more beautiful under the reflection of light, because the participation of light can make the color effect better. Based on this principle, for example, a professor like Japan invented the flash color-changing fiber. Fabrics made from this fiber vary in color and are fascinating. This fabric can be used to make garments, interiors, and the like.
1.2 Types of Color Changing Fibers The types of color changing fibers are roughly classified into photochromic fiber materials, thermochromic fiber materials, and electrochromic fiber materials and other color changing materials.
1.2.1 Photochromic fiber materials Photochromic materials are classified into organic and inorganic. The organic type includes a spiropyran derivative, an azobenzene derivative, and the like. The advantages of this type of color-changing material are: light coloring and achromatic block, but poor thermal stability and oxidation resistance, low fatigue resistance, and great environmental impact. Inorganic SrTiO3 doped with single crystal can photochromic, which overcomes the shortcomings of poor thermal stability and low fatigue resistance of organic photochromic materials, and is not affected by the environment. However, the inorganic photochromic material has a slower color and achromatic color and a larger particle size. Photochromic fibers are fibers obtained by blending a photochromic material and a high polymer by solution spinning, blend spinning or composite spinning techniques.
The photochromic fiber is a fiber whose color changes under the irradiation of sunlight or ultraviolet light, and reversibly changes back to the original color when the light disappears. Since the discovery of certain photosensitive properties of certain solid and liquid compounds in 1899, the study of various photosensitive materials has attracted great interest. Japan first developed photochromic composite fibers, and based on this, various photosensitive fiber products, such as embroidered velvet, knitting yarn, woven yarn, etc., were used for decorative leather, sports shoes, sweaters, etc., which were widely loved by people. .
There are many examples of photochromic fiber materials. For example, acrylic fabrics are dyed and finished with a cationic dye with color-changing molecules, and then discolored under different light sources, so it is called a color-changing knitted fabric. Leveling agent and acid agent have certain influence on the color change effect. The experimental results show that the fabric has the best color change effect by using 1227 leveling agent and glacial acetic acid. The color-changing acrylic knitted fabric must be unfolded before drying, and the drying temperature should be 98 ° C ~ 100 ° C. The fibers and fabrics prepared by this method have different color tones at different wavelengths of light, and all belong to photochromic fiber fabrics. In addition, a Japanese company will absorb the ultraviolet light of 350nm ~ 400nm wavelength and then change from a colorless to a light blue or dark blue spirofuran photosensitive material wrapped in microcapsules, used in the printing process to make photosensitive color-changing fabric. Microencapsulation can increase the antioxidant capacity of the photosensitizer, thereby extending the service life. Photochromic T-shirts produced using this technology have been supplied to the market in 1989. In recent years, similar products have been sold in China.
1.2.2 Thermochromic fiber Thermochromic fiber refers to a fiber whose color changes with temperature. The method for obtaining the thermosensitive color-changing fiber can be obtained by applying a solution of a thermochromic microcapsule-containing vinyl chloride polymer to the surface of the fiber and heat-treating the solution to form a gel. Reversible thermochromic effect.
For example, in 1988, Toray developed a temperature-sensitive fabric, Sway, which seals the heat-sensitive dye in a capsule of 3 to 4 m in diameter and then coats it on the surface of the fabric. The microcapsules of the glass substrate contain three main components: a thermochromic pigment; a color developer which combines with the pigment to exhibit another color; and a coloring and coloring which can be combined at a certain temperature. An alcohol-based decolorizer that separates and dissolves a pigment or a color developer. The microcapsules whose color changes with temperature can be obtained by adjusting the composition ratio of the three, and the change is reversible. It has 4 primary colors, but can be combined into 64 different colors.
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