EFFECT OF SELECTED CHLORINATED SOLVENTS ON THE PHYSICOCHEMICAL PROPERTIES AND DYEABILITY OF POLYESTER FIBRE

Abstract

The effect of chemical treatments on the structure and properties of polyethylene terephthalate fibre have been studied. Polyethylene terephthalate (PET) fibres were isothermally treated at room temperature with four chlorinated solvents: perchloroethylene (PCE), trichloroethylene (PCE), 1,1-Dichloroethylene (1,1-DCE) and tetrachloromethane (TCM) for 30, 60, 150, 300, 450, 600, 750, 900 and 1800 secs respectively. The treatment was found to influence the morphology and properties of the polymer to an extent which depends not only on the time of treatment but also on the nature of the liquid and the forces of interaction in the PET: liquid pair being considered. The treatments have been found to induce considerable shrinkage of the fibre in the following order: 1,1-DCE > PCE > TCE > TCM. This trend was found to be contrary to that of the percentage crystallinity (calculated from the CDT values) of the order: TCM > TCE > 1,1-DCE > PCE. The observed changes in the morphology of the treated polyester have been related to improvement in some end use properties such as mechanical and dyeing properties of the polymer. There is a fall in the modulus (MPa) of the treated fibres compared to the control ones due to the reduction in stiffness of the phenyl residue on the terephthalate group while increase in tenacity (MPa) and extension at break (mm) of the treated fibres was ascribed to the stability conferred on the fibre by the solvent treatments. Increase in the dye uptake was observed in all the treated fibres. The TCE pretreated fibres gave the highest value of dye uptake at the expense of 1,1-DCE with the highest shrinkage and liquid retention values which could be explained in terms of high amount of oligomer loss as well as greater scissions observed on the surface of TCE treated fibres. The dyeing of treated and control polyester fibres in trichloroethylene at 40 oC and 60 oC was also carried out. An improvement in the dye uptake observed in the solvent dyeing compared to the aqueous one was found to be temperature dependent. Study on the surface morphology of the pretreated fibres using the scanning electron microscope (SEM) showed surface roughening and scissions compared to the smooth surface on the control fibre, these surface roughening and scissions are required for better deposition of the dye. The x-ray diffractographs also revealed reduction in the peaks which is an indication of increase in the amorphous percentile of the treated fibres over the control sample. Studies on the surface dye wash or (stripping) which is commonly referred to as reduction clearing of the dyed fibre in textile processing was done. From the results, the four chlorinated solvents showed a good tendency of being used as levelling agent to correct an unevenly dyed fabric and to remove excess dye from the fibre surface. Generally, the results of this research work revealed that the chlorinated solvents have been able to modify the surface morphology of the polymer with an improvement in some other end use properties. TCM as a solvent showed an improved ability to induce better dimensional stability of textile materials during processing, use and dry cleaning stages.