| Polyethylene terephthalate (Polyester) has been one of the most popular synthetic fibers in textile industry for more than twenty years. However, the hydrophobic character of polyester results in certain problems. The purpose of this study is to improve the hydrophilicity as well as dyeability of polyester.; Microwave heating was used as the energy source of this study because of its potential energy savings and uniform rapid heating of the solvent media. Polar aprotic solvents capable of absorbing microwave energy and swelling the polyester structure, such as N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO), as well as water were used. In order to level off the treatment temperature to about 100(DEGREES)C, DMF/H(,2)O and DMSO/H(,2)O mixtures at 1:1 volume ratio were used instead of pure nonaqueous solvent, and a five minute period as the treatment time was used. To improve the hydrophilicity of polyester, two bases, e.g. sodium hydroxide and triethanolamine were added into the solvent systems.; The effect of nonaqueous solvents and water treatments on polyester was examined in the presence and absence of the alkaline additives. The treated polyesters were examined and characterized by measurement of density, intrinsic viscosity, dyeing characteristics, thermal properties, hydrophilicity, tensile properties, and crystallinity. The surface morphology of the treated fibers was also examined through scanning electron microscopy. The changes in surface morphology and properties of the treated polysters are examined in light of the chemical and physical processes induced by solvent-assisted treatments.; It is found that the polar aprotic (nonaqueous) solvents, e.g. DMF and DMSO penetrate the polyster and force oligomers to the surface of polymer more readily than the polar protic solvent, e.g. water. The effect of the nonaqueous solvent treatments are more significant than those of water treatment alone in most properties including weight uptake, dimensional change, density, dyeing properties and in the drop absorbency test for DMSO/H(,2)O. Scanning electron micrographs also show that the treatments with the nonaqueous solvent systems generate more particles of larger size in irregular crystal form on the fiber surface and a very small number of cracks on the fiber surface are observed. From all these changes it is apparent that microstructural changes do occur in the polyester although atomic scale structural changes are not detected by x-ray diffraction.; The alkaline additives hydrolyze the polyester fiber, cause weight loss, and interfere with solvent-induced shrinkage. The dye affinity of dibasic and amphoteric anthraquinone dyes for polyester are markedly increased by the base treatments while the affinity of the diacid dye, 1,4-dihydroxyanthraquinone on the treated polyester does not increase due to the combined effect of shrinkage and an increase in acid end groups of the hydrolyzed polyester. The hydrophilicity of polyester is improved, particularly in H(,2)O and DMSO/H(,2)O with 0.1% NaOH. Base additives have little additional effect on tensile properties and differential thermal analysis curves of polyester compared to the solvent treatments alone. The surface morphology is significantly changed by the base additives however. The base treatments generate pits and cracks on the surface of the polyester fiber. The DMSO/H(,2)O system enhances basic hydrolysis more than the DMF/H(,2)O system; and 0.1% NaOH causes a higher rate of hydrolysis than 1% triethanolamine. Triethanolamine may cause internal hydrolysis evidenced by the fibrillar texture on the surface of the fiber. The texture is particularly obvious in DMF/H(,2)O system which is prone to extract and precipitate polymer particles and oligomers on the surface instead of removing them.(, )... |
