Chemistry and Application of Leuco Dyes

This will help you alot in under standing about leuco dye and its modern applications

1. CHEMISTRY AND APPLICATION OF LEUCO DYES PRESENTED BY: ASMA MUQADAS ROLL # 7632

2. Contents Dyes Natural & synthetic Dyes Leuco Dyes Application Method Properties Two forms of Leuco Dyes Classes of Leuco Dyes Applications Limitations References

3. Dyes The colored, ionizing and aromatic organic compound to which it is being applied. Dyes are applied to numerous substrates e.g. textile, ,plastic, paper, etc. Certain kind of dyes can be toxic, carcinogenic or mutagenic and can pose as a hazard to health . Dyes are the larges group that can easily be influence to our liking.

4. Natural and Synthetic Dyes Natural dyes are get from natural resources such as plants, invertebrates and minerals. T he first synthetic organic dye, mauveine, by William Henry Perkin in 1856. Synthetic dyes replaced the natural dyes. Cost less, range of new colors. Imparted better properties to the dyed materials. Special and high technology application .

5. Dyes Give Colors Due to the presence of Chromophore. Chromophores are the groups which imparts color.

6. Leuco Dyes Certain leuco Dyes insoluble in water. The term Leuco, meaning white and was applied to the reduced form of vat dyes. Change color on oxidation or with fluctuating of temperatures. The products found in forms of slurry, powder, solvent-based ink, epoxy, master batch, etc.

7. Method of Application These dyes are insoluble in water. Reduce with sodium hydrosulphite yield alkali soluble forms ( Leuco-compounds). It is in this form they are introduced into the fabric. The reducing operation carried out in wooden vats .

8. …………… After the reduction, dye has been absorbed in the fiber. The original insoluble colored dye is reformed by oxidation with air or chemical. These dyes are used to dye cotton etc. Very fast because of their insolubility in water. e.g. Indigo

9. Forms of Leuco dyes Colorless. Colored when changing temp. e.g. Spiro form Oxazine form

10. Classes of Leuco Dyes

11. 1.Triphenylemethane Aniline green,  malachite green , or china green Synthesis

12. Applications of Malachite Green Used pharmaceutically in dilute solution as a local antiseptic. Effective against fungi and gram-positive bacteria. In the fish-breeding industry it has been used to control the fungus   Saprolegnia . Used as a dye for silk ,wool, jute, leather and to dye cotton that has been mordanted with tannin.

13. Sulfur Dyes Inexpensive complex reaction mixtures of selected aromatic compounds with sodium polysulfide.

14. Synthesis Sulfur black

15. Applications U sed for black, blue, brown, khaki and green colors. A pplied to cellulosic fibers and blends of cellulosics with polyester, nylon and acrylics.   E xcellent results at a relatively low cost. With good application methods, sulfur dyes are extremely wash-fast. N ot fast to chlorine bleaching.

16. ….. ….. Dark and medium colors are most common Light colors can be produced by special procedures involving: B lended reducing agents. Blends of surfactants. Controlled oxidation. Preparation methods like Mercerizing and bleaching.

17. Indigo Dyes Indigo dye is an organic compound with a distinctive blue color. Natural indigo get from a plant ‘ indigofera tinctorie’. 1 st Synthetic indigo replace natural product in textile trade in 1897.

18. Synthesis Indigo Dye

19. Application of Indigo Dyes U se as a dye for cotton yarn , for the production of denim cloth for blue jeans . Use for dyeing wool and silk. ’Qing Dai’’ a Chinese name for Indigo natural it has a salty taste and cooling properties .

20. Application of Other Leuco Dyes A wide range of organic leuco dyes are available changing color between -5 °C and 60 ° C. Application wherever sharpness of the temperature change is not important. Novelties such as bath toys, color changing spoons, mugs and cups. Microwave temperature indicators on food packaging

21. Color Changing Cups

22. Thermal paper

23. Hair Color

24. Battery status indicators The Duracell indicator makes use of leuco dyes applied to a resistive strip indicating the heating temperature of the strip that is related to the battery's current deliver.

25. Color Changing Ducks The color changing ducks are covered with a layer of leuco dyes. Cold Hot

26. Flat Thermometer

27. Microencapsulation Process in which tiny particles are surrounded by a coating to give small capsules of many useful properties. Leuco Dyes require a special system i.e. combination of chemicals. This process is effectively shown in the photo- microgh .

28. Thermo chromic inks These are very high temperature uses Leuco Dyes change color with changes in temperature.  LD's are reversible. It takes about a 5ºF (3ºC) temperature change for the LD to change color.

29. Cold Activated Thermo chromic Ink It is used on labels and packaging to create a color change when cooled. (Clear to Color at 15ºC / 59ºF ).

30. Touch Activated Thermochromic Ink : •    It will vanish when rubbed or touched to reveal an image or another color printed beneath. (ColortoClearat31ºC/88ºF ).  

31. High Temperature Thermo chromic Ink It is designed to change color just below the pain threshold alerting consumers and users to a safety hazard - Too Hot! (Color to Clear at 47ºC / 117ºF ).

32. References 1. Chemistry and Applications of Leuco Dyes by Ramaiah Muthyala Springer, 30-Jun-1997. 2. Industrial Dyes, Chemistry, Properties, Application by Klaus Hunger 3. Kolorjet Chemicals Pvt. Ltd. 4. LCR Hall crests Thermodynamic Leuco Dyes. 5. Gilbert N. Lewis, Jacob Bigeleisen J. Am. Chem. Soc., Photochemical Reactions of Leuco Dyes in Rigid Solvents. Quantum Efficiency of Photo-oxidation., 1943, 65 (12), pp. 2419–2423 6. Thermochromism in commercial products" M A White & M LeBlanc 7. Journal of Chemical Education, Vol 76, No 9, P 1201, Sept 1999. 8. en.wikipedia.org/wiki/ Leuco _dye. 9. Marjan Kooroshnia The Swedish School of Textiles, University of Boras, Boras Sweden. [email protected]

33. THANK YOU