THE USE OF AQUEOUS ALKALINE-HYDROLYSIS TO REVEAL THE FINE-STRUCTURE OF POLY(ETHYLENE-TEREPHTHALATE) FIBERS

The fine structure and physical properties of bright and semidull poly(ethylene terephthalate) (PET) fibers were investigated as successive layers of the polymer were removed by hydrolysis using aqueous solutions of sodium hydroxide up to weight losses of 90 and 68%, respectively. For both types large changes in molecular weight distribution did not occur, although as weight loss increased, the density of the remaining fiber increased. Alterations in fine structure with weight loss were also observed by thermal analysis. Greater strength loss with decreasing weight occurred for the semidull fiber than for the bright sample. Larger pits formed on the surface of the hydrolyzed semidull fibers than on the surface of the bright products. This observation is attributed to the titanium oxide present in the semidull fibers. It was also noted that as the density of the bright PET samples was increased by heatsetting, the rate of hydrolysis decreased.