In the field of nylon and polyester fibers, there has been a tendency in recent years for the Direct Spin Draw (DSD) process to become the mainstream technology. However, in the case of Polypropylene (PP), fibers with high tenacity could not be obtained using the DSD process because PP fibers could not be drawn to high draw ratio. To solve this problem, a new DSD (I-DSD) process was developed. In this process, a contact-type cooling take-up roll was installed after the melt spinning stage and an as-spun fiber was drawn after it was force cooled. It was possible to effectively control the crystallinity of as-spun fibers and increase the maximum draw ratio of the fiber to as high as 9 even when drawing was carried out on an in-line basis. This high draw ratio was almost equal to that obtained in the Offline Drawing (OFD) process. In addition, it was found that as-spun fiber with lower crystallinity had a higher maximum draw ratio. A negative correlation coefficient between the crystallinity and the maximum draw ratio of as-spun fiber was found for the I-DSD process.

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In the field of nylon and polyester fibers, there has been a tendency in recent years for the Direct Spin Draw (DSD) process to become the mainstream technology. However, in the case of Polypropylene (PP), fibers with high tensile strength could not be obtained using the DSD process because as-spun fibers could not be drawn to high draw ratio.
To solve this problem, a new DSD (I-DSD) process was developed. In a previous paper, studies on the effect of installation of a cooling take-up roll on the structure and drawability of as-spun fibers were carried out. In this paper, the structure of fibers obtained in the following three processes was examined: (1) the I-DSD process, (2) the conventional-type DSD (C-DSD) process and (3) the offline drawing (OFD) process in which drawing is carried out on an offline basis. There was a large difference in the structure of fibers drawn to the same draw ratio in the C-DSD process and the other two processes. The fiber obtained by the C-DSD process was found to have higher crystallinity and higher birefringence values compared with the other two. On the other hand, the highest melting point of fiber was obtained in the OFD process, followed by the I-DSD process, and then by the C-DSD process. It was found that a fiber with a lower melting point had a shorter “long period”.
In addition, the tensile strength of fiber obtained by the C-DSD process was the highest among the fibers obtained by the three processes when compared at the same draw ratio. However, because the draw ratio could only be increased to about 3-4, its tensile strength could only be raised to around 0.30GPa. On the contrary, the draw ratio of fiber obtained in the I-DSD process, as in the OFD process, could be increased to about 9, so that it was possible to obtain fibers whose tensile strength was high or about 0.51GPa.

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An uneven thickness distribution can cause serious problems in practical applications. In this report the deformation and thickness behavior of poly (ethylene terephthalate) (PET) film during transverse stretching in a tenter is discussed. The experiments were performed in a pilot plant with extrusion, casting, machine direction (MD) stretching, transverse direction (TD) stretching and thermosetting and winding processes. The thickness distribution of the PET film was measured after uniaxial orientation (MD stretched) and again after biaxial orientation (TD stretched in the tenter). The thickness behavior during the transverse stretching in the tenter was calculated by a finite element method (FEM), assuming a rigid-plastic or elastic-plastic constitutive law with parameters determined from the tensile stress-strain measurements. The tensile stress-strain tests were performed on MD stretched film in the transverse stretching direction. The FEM analysis was carried out using the measured initial thickness distribution of the uniaxially oriented film (MD stretched). It was estimated from this analysis that the (TD) stretching of the film in the tenter initiated near the tenter clip (edge of film), spread to the center of the film and then finally moved from the center to the edge of the film under the experimental conditions of this study. Good agreement was obtained between the experimental and predicted FEM results for the final film thickness distribution after transverse stretching.

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Superstructural changes during uniaxial deformation of Thermoplastic Polyester Elastomer (TPEE) films having different composition ratios of poly (butylene terephthalate) (PBT) and poly (tetramethylene glycol) (PTMG) were studied. Evaluations were done using polarizing microscope, small-angle light scattering (SALS), thermal analysis, dynamic mechanical measurement, tensile test and infrared spectroscopic analysis. It was found that the spherulitic superstructure existed in all samples, and the optical axis in the spherulite depended on the basic composition of TPEE. In the case of large PBT composition, the crystal transition from α-form to β-form occurred due to elongation. It was thought that this was caused by the transmittance of external force to the PBT crystallite. Furthermore, spherulites having large PBT composition were collapsed by elongation. Those with small PBT compositions showed the elastic recoverable property on cyclic deformation. It can be called as spherulite eastomer.

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The energy balance on the laser drawing process of poly (ethylene terephthalate) was analyzed by the on-line fiber temperature measurement. The energy converting process from the external work for drawing to the thermal energy was quantitatively investigated by comparing the measured temperature profiles with the estimated temperature profiles using energy balance equations. From the result, it was shown that 9-24% of the applied work was stored as the elastic energy into the system just after the neck drawing point, and that the stored elastic energy was released as the thermal energy with the progress of orientation-induced-crystallization. It was also shown that the ratio of stored energy to the applied work tend to increase with the increase of fiber speed.

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