Abstract
We conducted a preliminary study on fiber structural development in the high-speed melt spinning of environmentally friendly polyethylene terephthalate (Ti-PET) synthesized with 25 ppm of titanium-based catalyst, which was compared with conventional PET (Sb-PET) synthesized with 260 ppm of antimony-based catalyst. Gel permeation chromatography of Ti- and Sb-PET resins of intrinsic viscosity 0.63 confirmed that both resins have similar molecular weights and distributions. However, differential scanning calorimetry revealed that the Ti-PET resin exhibited a lower melt–crystallization peak and isothermal melt-crystallization rate than the Sb-PET resin. High-speed melt spinning of the Ti- and Sb-PET was possible up to a spinning velocity of 6 km/min. Two-dimensional wide-angle X-ray diffraction analyses showed that the molecular orientation of the obtained as-spun Ti- and Sb-PET fibers increased with spinning velocity, and a highly oriented, crystalline structure by orientation-induced crystallization started to appear from 5 km/min. Notably, Ti-PET fibers showed a lower degree of crystalline structural development and lower tensile strength compared with Sb-PET fibers under the high-speed spinning conditions. Our results suggest that the catalyst in PET resins can act as nucleating agents in thermal- and orientation-induced crystallization, and that differences in catalyst content can influence PET fiber structure development under extreme conditions in high-speed melt spinning.
Highlights
(ethylene terephthalate) (PET) is a thermoplastic polymer widely used in synthetic fibers and for various applications, such as films, bottles, and molded plastic parts [1,2,3]
Approximately 244 ppm of residual elemental Sb was detected in the Sb-PET resin, as shown in Table 2, while it was not detected (ND) in the Ti-PET resin
Ti-PET determined by gel permeation chromatography (GPC) showed similar values to those of Sb-PET. These results indicate that the Ti-based catalyst shows good performance for PET polymerization, despite its loading usage being approximately 10 times lower than that of the conventional Sb2 O3 catalyst
Summary
(ethylene terephthalate) (PET) is a thermoplastic polymer widely used in synthetic fibers and for various applications, such as films, bottles, and molded plastic parts [1,2,3]. Commercial PET resins are mostly produced via two-step polymerization, comprised of esterification and condensation using raw materials, such as ethylene glycol (EG) and terephthalic acid (TPA), or EG and dimethyl terephthalate (DMT). Titanium (Ti)-based catalysts are one of the most commercially available catalysts employed as Sb-based catalyst substitutes, and have attracted manufacturers’ attention due to their excellent performance resulting from their large surface area (due to their high porosities and particle sizes), environmental friendliness, and low cost compared to the other Sb-free catalysts [5,14,15]. Ti-based catalysts show good performance with relatively low catalyst loadings (TiO2 10–30 ppm) compared to those of Sb-based catalysts (Sb2 O3 150–300 ppm) in polymerization [16,17,18], and form fewer by-products, such as oligomers, during PET melt spinning than Sb-based catalysts, [5,19,20,21]
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