Hypercolor
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Hypercolor was a line of clothing, mainly T-shirts and shorts, that changed color with heat. They were manufactured by Generra (now a division of Public Clothing Company) and marketed in the United States as Generra Hypercolor or Generra Hypergrafix and outside the US as Global Hypercolor. They contained a thermochromic (temperature sensitive) pigment made by Matsui Shikiso Chemical of Japan, that changed between two colors–one when cold, one when warm. The shirts were produced with several color change choices from beginning in 1991. [1] The effect could easily be permanently damaged, particularly when the clothing was placed in a hotter than recommended wash. In 2003, Wickedglow Industries, Inc, under the trade marked name Body Faders, introduced a completely revised and reformulated hypercolor line of clothing. Superior in color-fastness and durability over the Generra product, the Michigan company continues to produce apparel, screen printing and accessories to this day.
[edit] Principle
Substances that can change color due to a change in temperature are called thermochromes. There are two types of thermochromes: liquid crystals (used in mood rings) and leuco dyes (used in hypercolor T-shirts).
The colour change of Hypercolor shirts is based on combination of two colors: the colour of the dyed fabric, which remained constant, and the colour of the thermochromic dye. The dye is enclosed in microcapsules, tiny (few micrometers in diameter) drops of liquid sealed in a transparent shell, bound to the fibers of the fabric.
When it is cold the mixture in the capsule is solid and the carbon molecules in the leuco dye are attached to each other in a ring shape. When the capsule experiences a rise in temperature the molecules change shape, just like liquid crystals. They break open the carbon ring. This change means that the dyes absorb and release light differently, and the colour we see is different.
The liquid is a leuco form of a dye (in this case crystal violet lactone), a weak acid (benzotriazole), and a quaternary ammonium salt of a fatty acid (myristylammonium oleate) dissolved in a solvent (1-dodecanol). At low temperatures, the weak acid forms a colored complex with the leuco dye, interrupting the lactone ring. At high temperatures, above 24-27 °C, the solvent melts and the salt dissociates, reversibly reacts with the weak acid and increases the pH. The pH change leads to closing of the lactone ring of the dye, which then regains its colorless (leuco) form.
Therefore at the low temperature the colour of the shirt is the combination of the color of the microcapsules with the color of the dyed fabric, while at higher temperatures the capsules become colorless and the color of the fabric prevails.
[edit] External links
- HowStuffWorks "Thermochromic Fabric Displays"
- "Generra's hypercolor line heats up" - Daily News Record, May 1991
- "Hypercolor is hot again" - L.A. Times, July 6, 2008
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[edit] duvets
Colour change can also be used in children's duvets to show whether they are too hot or too cold. This then stops the need for thermometers.
