One-step Dyeing and Durable Press Finishing of Cotton

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Title: One-step Dyeing and Durable Press Finishing of Cotton
Author: Li, Shiqi
Advisors: C. Brent Smith, Committee Member
Harold S. Freeman, Committee Chair
David Hinks, Committee Member
Peter Bloomfield , Committee Member
W. Gilbert O'Neal, Committee Member
Abstract: Cotton is one of the most commonly used fibers for textiles, as many garments are made from dyed and durable press (DP) finished cotton. Conventionally, cotton is dyed first, then finished with a crosslinking agent to obtain the desired color and DP properties. If the two steps could be merged, significant savings in energy, chemicals, water, labor, and machine occupation time would be achieved. Since the 1950s, many researchers have attempted to combine dyeing and DP finishing processes into one step. However, a commercially viable one step dyeing and DP finishing process has not been reported. The main challenge has been producing treated fabrics that have deep shades, good washfastness, and excellent DP performance simultaneously. In the present research, two new one step dyeing and DP finishing processes were developed. One of the methods was a one step steam-cure process that included padding, drying, steaming, curing, and washing. The second involved a one step batch-dry-cure process composed of padding, batching, drying, curing, and washing. These methods afforded deep fabric shades (K/S > 15) and dye fixation levels > 95%. Washfastness was as good as that from a conventional reactive dyeing method and fabric DP properties were comparable to those from a separate DP finishing process. It was shown that reactive, direct, and even acid dyes could be used for dyeing cotton in these one-step processes. The mechanism of dye fixation on fabrics dyed using these processes was studied. By 1) varying dyes, DP agent levels, and application conditions, 2) characterizing the chemistry that occurs between dyes and DP agents on glass plates under standard finishing conditions, and 3) conducting extractions of fabrics and their powdered forms following one-step dyed and DP finished, the basis for dye fixation was established. The results of these experiments showed that the key to effective one step dyeing and DP finishing is complete dye diffusion before curing occurs. After curing, the DP agent connects adjacent cellulose chains to entrap the dye inside the fiber, which results in high dye fixation and good washfastness. This mechanism for fixing a dye on cotton is different from conventional mechanisms, which involve covalent bonding of reactive dyes to cellulose, cellulose substantivity through secondary valency forces for direct dyes, and mechanical entrapment through dye insolubility for vat, sulfur, and azoic dyes. It was also found that formaldehyde-based and non-formaldehyde crosslinking agents are suitable for one-step dyeing and DP finishing of cotton. The resultant dyed and finished fabrics had similar properties when DMDHEU or BTCA was used as a DP agent.
Date: 2009-08-01
Degree: PhD
Discipline: Fiber and Polymer Science

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