Doctoral Dissertations

Hageun Suh

Date of Award

5-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Human Ecology

Major Professor

Kermit Duckett

Committee Members

Gajanan Bhat, Larry Wadsworth, Spiro Alexandratos

Abstract

A possible candidate as an environmentally friendly nonwoven fabric is one which can be formed from the thermal calendering of a cotton/cellulose acetate blend. The results presented have focused on biodegradable properties of the fibers, physical properties of the fabric, and process optimization of the thermal calendering. Cotton, which is a comfortable, absorbent and biodegradable fiber was the base fiber in the nonwovens. Cellulose acetate (CA), which is a thermoplastic, hydrophilic, modified cellulosic fiber was used for the binder fiber. Biodegradation of cellulose has been intensively studied, and cellulose is believed to be readily biodegraded by many microorganisms due to the activity of cellulase enzymes catalyzing the hydrolysis and/or oxidation of cellulose. However, the biodegradability of CA is less than certain. To determine a semi-quantitative measure of the biodegradation of CA fibers, the standard test method of AATCC 30-1988 was selected. After a 12-week soil burial test, evidence of microbial attack on CA fabric was obtained on the basis of 27% strength loss. As a more reliable method for monitoring the activity of aerobic microorganisms, the ASTM test method D5209-91 was adopted. From the aerobic sludge test, the amount of CO2 evolved from the decomposition of CA, cotton and the fibers in the blend was measured. The biodegradability of CA fibers, with a degree of substitution of 2.5, was confirmed by showing carbon dioxide evolution. In addition, the synergistic effects of multienzyme systems between cellulase and esterase were suggested based on the increased biodegradation rates in fiber blends. Opening, blending, carding, and thermal calendering processes were used in the fabrication of the nonwovens. Pretreatment with solvent vapors was introduced for modifying the softening temperatures of CA and for lowering the calendering temperatures required otherwise. The success of the solvent-assisted thermal calendering is demonstrated in enhanced tensile strengths of the nonwoven. In addition, modification of tensile properties by solvent vapor pretreatment shows how enhanced strength can be obtained with lower calendering temperatures. Process optimization in thermal calendering is a necessary procedure to understand the bonding behavior of raw materials and to obtain the adequate properties of the resulting nonwoven fabrics. The experiment was designed for a 3-way factorial design (3x3x8) with the following factors: bonding temperature, blend ratio and solvent treatment time. The effects of the factors on a total number of 18 physical properties were determined by analysis of variance, least-square-means comparison, regression and correlation techniques. The results indicated that all the physical properties were significantly influenced by the bonding temperatures and the solvent treatment times. In addition, for optimal conditions, four responses were selected for stronger, softer, more extensible and more breathable nonwoven fabrics. The optimal processing conditions in a given blend ratio were suggested by a response surface technique based on multivariate-multiresponse analysis, and distance and desirability functions.

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