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Investigation of Dye-Fiber Reactions in SC-CO 2

Investigation of Dye-Fiber Reactions in SC-CO 2

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Investigation of Dye-Fiber Reactions in SC-CO 2

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  1. Investigation of Dye-Fiber Reactions in SC-CO2 NSF Green Processing Summer Research Experience for Undergraduates Faculty Mentors: Dr. David Hinks and Dr. Gerardo Montero Graduate Student Mentor: Mr. Ahmed El-Shafei North Carolina State University, College of Textiles Undergraduate Student: Nneka C. Ubaka-Adams Bennett College and North Carolina Agricultural and Technical State University

  2. Objectives • To demonstrate and quantify dye-fiber covalent bond formation between selected dyes and nylon, wool and cotton fibers in a supercritical carbon dioxide medium • To optimize reaction conditions (temperature, pressure and time) • To conduct a literature review

  3. Background • Conventional dye-fiber reactions use water as a transport medium, and result in: • Low reaction efficiency due to the competing hydrolysis reaction with hydroxyl ions in water (hydrolyzed dye cannot react w/fiber) • Environmental problems due to residual, unreacted/hydrolyzed dye present in effluent • Replacing water with supercritical fluids (SCF) as a transport medium can result in: • Eliminating toxic waste (no hydrolyzed by-product) • Lower costs for the entire dyeing process

  4. Conventional aqueous-based dye-fiber reaction Polyamide (nylon 6.6.)

  5. Dye-Fiber Reaction in SC CO2 Polyamide (nylon 6.6.) no hydrolyzed by-products

  6. Sulfonyl-azo-dyes

  7. Dyeing Procedure • Add fiber and dye to vessel • Pressurize system (with CO2) up to 800 psi and stir at approximately 850 rpm • Heat to required temperature (100 -180 ºC) • Pressurize to 3500 psi; hold for 2 hours • Release pressure, remove fabric

  8. Testing Dye-Fiber Reaction • Measure color strength (K/S) of each dyed fiber • Wash fiber with acetone (remove surface dye) • Conduct soxhlet extraction using ethyl acetate (to remove unreacted dye) • Compare effect of vinylsulfone reactive group on dye fixation

  9. Results

  10. Results

  11. Comparison of Dyed Fabrics

  12. Initial Conclusions • Color depth improved with increasing temperature • Strong evidence for dye-fiber bond formation using vinylsulfone-based dye on nylon and wool • ES-dyeing on wool fibers showed extremely low color yields after extraction (no reaction) • 94% fixation at 180 oC/ 3500 psi on wool

  13. Acknowledgements This research was conducted with the support of the NSF Green Processing Undergraduate Research Program with a grant from the National Science Foundation, Award Number, EEC-9912339.