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Abstract:
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American consumers generate more than 30 billion pounds of plastic wastes each
year. These plastics eventually break down into harmless products, but only after several
hundred years. Polylactic acid (PLA) fibers are produced from renewable resources, such
as corn. These biodegradable fibers can be used in applications such as apparel,
industrial, and institutional fabrics. The fibers have the same strength and elongation as
PET, but are lighter and softer than PET.
The objectives of this research were to study the effect of disperse dye structure
on dyeing behavior of PLA fabric, optimize dyeing conditions, evaluate colorfastness of
dyed PLA fabric, study the adsorption isotherm behavior of disperse dyes, and evaluate
the effect of fiber morphology on dye uptake and mechanical properties of PLA. Dyebath
temperature was varied from 70 to 130°C at 10°C intervals, pH from 4 to 8, and at a
holding time of 90 minutes. Although dye exhaustion was higher at 110°C compared to
100°C for most dyes, tensile strength and elongation losses were also significantly
higher at 110°C. At 130 DC, PLA filament yarns lost 100% of their tensile strength and
elongation. Mechanical property losses were the minimum at pH 5. Near maximum dye
exhaustion was observed in 20 to 30 minutes. High-energy azo and nitro diphenylamine
dyes exhibited high levels of exhaustion. Anthraquinone, methine, and quinoline dyes
had poor exhaustion. Overall, PET had better colorfastness properties and significantly
higher dye uptake compared to PLA fabric. The PLA fabric from a second source had
exhaustion similar to that of PET; however, losses of tensile strength and elongation were
significantly higher than for the previous PLA. Disperse dyes followed Langmuir and
Freundlich isotherms. A Nernst isotherm had a poor fit for all disperse dyes studied.
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