Clothing Materials Science-----Basic Knowledge of Clothing (Continued 2)

Third, light resistance

In the use and storage of clothing materials, oxidation due to the combined effects of sunlight and the atmosphere may cause deterioration of performance and decrease in strength, resulting in loss of use value. This phenomenon is called "aging" of clothing materials. The performance of the clothing material against the climatic effect is called weather resistance, and the performance of the function of the sunlight is called light resistance. Lightfastness is important for garments that are often used in the open air.

1. Fiber properties

The light resistance of fabrics varies with the type of fiber. Among the natural fibers and man-made fibers, the light resistance of wool and hemp is better; the light resistance of cotton and viscose fibers is poor; the light resistance of silk is the worst. Among synthetic fibers, acrylic fiber has the best light resistance; polyester has good light resistance, close to wool, and vinylon has poor light resistance and is close to cotton; nylon has poor light resistance and is similar to silk; and polypropylene and polyvinyl chloride have light resistance. Worst.

2. The nature of the fabric

The difference in light resistance of fabrics woven from various fibers determines the difference in application range and conditions. Because acrylic fiber has good light resistance and is the first of all kinds of fibers, it can be used as outdoor clothing for curtains, bedspreads, travelwear, swimwear, etc. The light resistance of polyester fabrics is second only to acrylic fiber and better than other fabrics. Outer clothes; although the woolen fabric has better light resistance, it should not be exposed to sunlight for a long time, otherwise it will lose the luster of the wool oil and yellow, giving people a sense of old and dry; silk and nylon fabrics are even more so. Because the ultraviolet rays in sunlight have embrittlement and destruction effects, long-term exposure, not only makes the color yellow, but also the strength is not lowered, so this kind of fabric is not suitable for outdoor use. In general, most fabrics should be dried in a cool, ventilated place, which not only helps to maintain the color of the fabric, but also extends the life of the fabric.

3. Detection method

The light resistance of clothing materials can be tested in two ways, namely open-air exposure and artificial simulation. The former has the advantage that the test conditions are relatively close to the actual wear conditions, and the disadvantage is that the test period is long and the reproducibility of the test results is poor. The latter is an instrument test method, which has the advantages that the temperature and humidity of the air and the radiation intensity can be controlled. The aging process of the test can be accelerated, and the test results are stable, but the disadvantages also exist, because the spectral distribution of the artificial light source and the sunlight used by the instrument are different. Therefore, the comparability of different test results is poor. In actual use, according to different needs, different methods can be used to test the percentage of strength loss of clothing materials after a certain period of time to reflect the degree of light resistance.

Fourth, chemical resistance

The ability of clothing materials to resist various chemicals is called the chemical resistance of clothing materials. This property has an important influence on the washing, descaling, dyeing, and bleaching of garments, because in these processes, the clothing materials will encounter different degrees of acid, alkali and oxidant, bleach and other chemicals. In addition, the treated fabric will have a certain impact on human skin health. Therefore, it is necessary to investigate the chemical resistance of clothing materials.

1. Fiber properties

The chemical resistance of various types of clothing materials can be considered from the characteristics of raw material fibers.

(1) Acid resistance: The acid resistance of protein fiber is better than the acid resistance of cellulose fiber. Therefore, wool and silk fiber can be made of no or little influence on the quality of organic acid or inorganic acid. Under normal circumstances, weak acid or low concentration of strong acid does not cause obvious damage at room temperature. With the increase of temperature and concentration, the damage of strong acid will increase accordingly. The acid resistance of cotton, hemp and viscose fiber is relatively poor. Whether it is strong acid, weak acid or organic acid or inorganic acid, it will destroy it to varying degrees. Cotton fiber is extremely unstable to inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, which will cause the fiber strength to decrease significantly. Generally, organic acid does not affect cotton; the stability of hemp to acid is better, it is not as sensitive as cotton, hot acid Will cause damage to the hemp, while cold concentrated acid will hardly affect hemp. Among the chemical fiber, polypropylene and chlorin have the best acid resistance; polyester has good acid resistance, and they have good stability to inorganic acids and organic acids; acrylic fiber has strong acid resistance and certain resistance to organic acids, but It will dissolve in concentrated sulfuric acid; the acid resistance of nylon is the worst in synthetic fiber, and all kinds of concentrated acid will decompose it; vinylon is not resistant to strong acid and easy to dissolve.

(2) Alkali resistance: Cellulose fibers are more resistant to alkali than protein fibers. Therefore, cotton, hemp and viscose fiber are resistant to dilute alkali at room temperature; while silk and wool have poor alkali resistance, and alkali has a strong corrosive effect on them, and the magnitude of the action varies with the concentration and temperature of the alkali solution. The higher the concentration, the higher the temperature, and the stronger the destructive power. In chemical fiber, polyester has the worst alkali resistance, and it has good stability to weak base. However, strong alkali will cause its surface to be corroded, and some surface will appear uneven; the alkali resistance of nylon is better than polyester; It will dissolve in strong alkali solution; the alkali resistance of vinylon and polypropylene is better; the chloride fiber is generally not affected by alkali at room temperature.

2. Fabric properties

Knowing the acid and alkali resistance of the fiber, it is not difficult to understand the inevitability of various fabrics used as work clothes in the chemical labor environment. Because weak acid or low concentration of strong acid has no significant damage to wool fiber, wool fabric can be dyed in weak acid dyes and can be used as acid-proof overalls; while cotton fabrics can be "silked" in lye. Treatment; polyester with the corrosive effect of strong alkali, is used to make polyester burnt fabric. People are looking forward to applying more chemical resistance to the use of clothing materials to produce more, better and more useful products.

3. Detection method

The acid and alkali resistance of the test garment material is generally expressed by the degree of decrease in strength or the degree of change in the weight of the material, coloring, etc. in a solution having a certain temperature, a certain concentration and a certain pH value. There is currently no standard test method that can be called a uniform.

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