HIGH-PERFORMANCE POLY(ETHYLENE-TEREPHTHALATE) FIBER PROPERTIES ACHIEVED VIA HIGH-SPEED SPINNING WITH A MODIFIED LIQUID ISOTHERMAL BATH PROCESS

A liquid isothermal bath (LIE) was used in the spinline to produce hig h performance poly(ethylene terephthalate) (PET) fibres at high speed melt spinning in a one step process. The take-up stress was measured u nder various spinning conditions. It was found that maximum applicable take-up stress was determined by the state or morphology of the filam ent before entering the liquid bath. To render the filament more amena ble to a preferred morphological texture prior to its entry into the l iquid bath, a small amount of hot liquid was applied to the running fi lament at a position upstream of the liquid bath. The results show tha t rapid cooling leads to a non-uniform fibre structure and the loss of subsequent filament deformability. However, the prolongation of atten uation, attendant the heating of the filament before entering the liqu id bath, induced uniform radial structure and an increase of deformabi lity. Then the maximum operable liquid depth within the LIE could be a ttained. Furthermore, the delay of attenuation in the upper portion of the liquid bath and the attendant increase of stress within the liqui d bath also resulted in an increase of the tensile properties. The mod ified LIE process was suggested as a further control of the temperatur e profile upstream of the liquid bath. High tenacity (9.7 g d(-1)), hi gh modulus (>120 g(-1)) and high load at a specified elongation of 5% (LASE-5) (>4 g d(-1)) PET of as-spun fibres are achievable using the m odified LIE one step process. The as-spun fibres produced with the mod ified LIE process have high amorphous orientation, low crystallinity a nd relatively large crystallite size. After drawing and annealing, the fibres exhibit desirable characteristics of high tenacity (>11 g d(-1 )), high modulus (>140 g d(-1)), high LASE-5 (5.8 g d(-1)), and low sh rinkage (<6%). (C) 1997 Elsevier Science Ltd.