For accommodating the enhanced frictional stress experi-enced by the running filament due to the presence of the liquid layer, it was assumed that the force due to liquid friction is 100 times larger than that of the air. This assumption was made on the basis of the data obtained from the on line measurement of the tension in a high-speed melt spinning line modified with a water bath [2]. Since liquid media are highly efficient in transferring the heat, it was assumed that the filament instantaneously attains the liquid temperature as it enters the liquid layer. Simple Newtonian viscous flow with the Arrhenius type temperature dependence was assumed above the glass transition temperature (Tg). The effect of crystallization was incorporated by making an assumption that the filament abruptly solidifies at a crystallization temperature which should be higher than the Tg of PET. The predicted temperature and diameter profiles at a take-up velocity of 4 km/min are presented in Figs. 10 and 11, respectively. In the simulation it was assumed that filament deforms until it cools down to Tg. As mentioned earlier, if the LIB is set at 150 cm the temperature of filament is almost the same as that of the liquid whereas when the LIB is set at 200 cm the filament temperature rises about 40°C when it enters the liquid. From the diameter profile it can be seen that the defor-mation of the filament above the LIB is much smaller as compared to the standard spinning. However, below the liquid surface, the filament attenuates rapidly apparently due to the enhanced frictional stress experienced by the running filament due to the presence of the liquid. Fig. 6 (left). Tenacity of as-spun fibers as a function of take-up velocity Fig. 7 (right). Young's modulus of as-spun fibers as a function of take-up velocity Fig. 8 (left). Plot of Young’s modulus vs birefringence for as-spun fibers Fig. 9 (right). Elongation at break of as- spun fibers as a function of take-up velocity International Polymer Processing downloaded fro