HIGH-SPEED MELT-SPINNING OF PET

The high-speed spinning process of poly(ethylene terephthalate) (PET) was modified by introducing a liquid isothermal bath (LIB) which was k ept at a temperature of 155 degrees C and placed at a distance of 150 cm or 200 cm below the spinneret. The structure and mechanical propert ies of the as-spun fibers thus produced in the take-up speed range of 1 to 7 km/min were characterized The results showed that the introduct ion of the LIB significantly influences the structural development of the as -spun fibers. The fibers produced using the LIB in the spinline showed significantly higher birefringence and crystallinity compared to the fibers produced using a standard high-speed spinning process. A semi-quantitative numerical simulation was performed with the incorpo ration of the LIB in the spinline to understand the mechanism of fiber structure formation during the modified high -speed spinning process of PET. The results showed that the solidification stress is considera bly high when the solidification was assumed to occur at a position cl ose to the exit of the LIB. The enhancement of molecular orientation w as attributed to the increased frictional stress induced by the liquid layer whereas the spinline crystallization was found to be influenced strongly by the temperature of the liquid.