EFFECT OF HEAT-SETTING TEMPERATURE ON ALKALI HYDROLYSIS OF POLY(ETHYLENE-TEREPHTHALATE) FIBERS

Poly(ethylene terephthalate) (PET) fiber was heat set at 100 to 220-de grees-C and then hydrolyzed with 10% aqueous sodium hydroxide solution at 90-degrees-C for 60 and 120 minutes. Weight loss from the alkali h ydrolysis initially decreased with increased heat-setting temperature up to 140-degrees-C and then increased at temperatures above 140-degre es-C. This phenomenon is similar to those with hydrazine treatment and with disperse dyeing of heat-set PET fibers and can be attributed to changes in the fine structure, especially in the amorphous regions of the fiber, caused by heat-setting treatment at different temperatures. Crystallinity and disperse dye uptake for the hydrolyzed PET fiber in creased with hydrolysis, indicating differences in the fine structure from the outer to the inner regions of the fiber.