Clothes, color-changing

Thermochromic dyes change color with temperature (heat). The effect may be due to a single dye or a composite system, and the color change may be reversible or irreversible. Thermochromic dyes find use in direct thermal printing and as temperature sensors, as well as in clothing and novelties. 

In addition, the shapes of the curves are the same as those found from measurements of degree of polymerization, color change and tear strength for the degradation of cotton, linen and rayon cloth artificially aged under the same conditions (12. 14. 21). 

It has been shown that changes in the UV and IR absorbance of unplasticized Cellophane films subjected to accelerated aging in a dry oven at 140 °C follow the behavior predicted by a first-order kinetic model, except for deviations in the early aging period, and that these deviations are most likely caused by oxidation products in the films. It has also been shown that, for Cellophane films, the changes in UV and IR absorbance follow the same kinetics as color change, and that these kinetics are nearly identical with those for rayon and cotton cloths aged under similar conditions. 

Tables I-IV summarize the preceding results in terms of the ratios of tetrahydridoborate-treated to water-washed cloth for color change and strength retention. Table I shows that the TMA treatment does little to affect the change in color of new or slightly degraded cloth, but it is quite effective for those cloths that have been aged significantly. Table II yields similar conclusions for NaBHi, although NaBHi does not appear to do as well as TMA. This result indicates that extremely long...

Table I. Color Change TMA-Treated Versus Water-Washed Cloths...

Note-. Values are the differences in color change at 150 °C between new cloth that was washed with water and new cloth that was treated with TMA. Negative values mean that the water-washed cloth was less discolored than the treated cloth. 

M9 paper is an adhesive-backed, tape-like material designed to be worn on the outside of clothing or placed on vehicles, equipment, or supplies that may be exposed to liquid CWA droplets. The detector responds with a marked, contrasting color change, turning from the original green to red or pink when it comes in contact with a liquid CWA droplet. 

Freshly distilled 4-VP was mixed with dihaUdes (molar ratio 2 1) in bulk or in solution. The polymerization proceeded to virtual completion in bulk or in solvents (benzene, methanol, dimethylformamide (DMF) or mixtures of DMF with methanol) and in presence of e.g., silica gel, carbon black, sand, porous materials, e.g., paper, cloth, polyacrylonitrile fibers, etc. The rate of polymerization was significantly enhanced in absence of air or by COy irradiation. The mixtures of 4-VP and dihalides were left at room temperature for periods of 5 days during which time the color changed from colorless to pink or red. The resin was isolated by addition of acetone and washing with acetone. After drying it was obtained in the form of a light yellow powder in yields of 70 to 100% of the theoretical amount. 

As early as 2500 bce m India indigo was used to dye cloth a deep blue The early Phoenicians discovered that a purple dye of great value Tyrian purple could be extracted from a Mediterranean sea snail The beauty of the color and its scarcity made purple the color of royalty The availability of dyestuffs underwent an abrupt change m 1856 when William Henry Perkin an 18 year old student accidentally discovered a simple way to prepare a deep purple dye which he called mauveme from extracts of coal tar This led to a search for other synthetic dyes and forged a permanent link between industry and chemical research... 

William Henry Perkin, an 18-year-old working in the back room and outdoor shed of his London home, had discovered in black coal tar a beautiful purple dye that would change the world. For the first time in history, color could be democratized. William Henry Perkin and his purple, later known as mauve, rescued the poor and middle classes from their age-old austerity of hues. Natural dyes were expensive and, before Perkin s synthetic mauve, millions of poor people lived their lives in untreated drab and dingy fibers. Even for the middle class, pieces of brilliantly dyed cloth were treasures to be reused from garment to garment and from year to year. It was the schoolboy William Henry Perkin and his successors who would give the world the ample abundance of tints that only the rich had previously enjoyed. 

Application of photochromic materials was first exploited by Alexander the Great. He designed a crude timepiece for his soldiers consisting of a chemically treated cloth worn on the left forearm. Under the action of the sun, the cloth changed colors each hour and provided Macedonian troopers with the world s first wristwatch. Among historians it is known as Alexander s Rag Timeband (8). 

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