Influence of Branching on the Structure and Properties of Poly(ethylene terephthalate) Fibers obtained by High-speed Melt Spinning
Chen Xu, Hiorshi Ito, Takeshi Kikutani
Tokyo Institute of Technology
Japan
Keywords: high-speed melt spinning, branched PET, orientation crystallization
Standard poly(ethylene terephthalate) (PET) and PETs modified by 0.1 wt% and 0.3 wt% of trimethyl trimellitate (TMTM) with respect to the amount of dimethyl terephthalate were used. The DSC and GPC-MALLS analyses were conducted to characterize the branching of polymers.
These polymers were subjected to the high-speed melt spinning process at the take-up velocity ranging from 1 to 7 km/min. On-line measurement of the filament diameter along the spinning
line was also carried out. By means of the measurements of birefringence, density and wide-angle X-ray diffraction (WAXD) pattern, the molecular orientation and the crystallization
behavior of the as-spun fibers were investigated. The mechanical properties of the as-spun fibers were also investigated by the tensile testing. As to the TMTM 0.1 wt% PET fiber, the position of the neck-like deformation was obviously closer to the spinneret in comparison with the standard PET. It is the indication of higher
crystallization temperature. The orientation increased with an increase in the take-up velocity, while the increase of the TMTM amount caused a significant drop in molecular orientation
especially at take-up velocities above 4 km/min. Although the maximum density of the branched PET fiber was lower than that of the standard PET fiber, at 4 and 5 km/min, the density of TMTM 0.1 wt% PET fiber was higher than that of the standard PET fiber. This result indicates that in the TMTM 0.1 wt% PET fiber, the orientation-induced crystallization started from lower take-up velocities despite of the suppression of ultimate crystallinity, which was caused by the
incorporation of the branching. Parameters representing the physical network structure in the as-spun fibers was analyzed based on the classical rubber elasticity theory to elucidate the mechanism of the enhancement of orientation-induced crystallization in the PET polymers with branching