This work examines the PBT/PET sheath/core conjugated fiber, with reference to melt spinning, fiber properties and thermal bonding. Regarding the rheological behaviors in the conjugated spinning, PET and PBT show the smallest difference between their melt‐viscosity at temperatures of 290°C and 260°C respectively, which has been thought to represent optimal spinning conditions. The effect of processing parameters on the crystallinity of core material‐PET was observed and listed. In order of importance, these factors are the draw ratio, the heat‐set temperature, and the drawing temperature. The crystallinity of sheath material‐PBT, however, can be considered to be constant, independent of any processing parameters. The bulk orientation, rather than the crystallinity of PET core, dominates the tenacity of PBT/PET sheath/core fiber. Moreover, heat‐set treatment after drawing is recommended to yield a highly oriented conjugated fiber. With respect to thermal bonding, PBT/PET conjugated fibers processed via high draw ratio but low‐temperature heat setting can form optimal thermal bonds at a constant bonding temperature of 10°C above the Tm of PBT.
This study investigates melt spinnability of ethylene vinyl alcohol (EVOH) copolymers with various ethylene contents, which exhibits excellent biocompatibility but cannot easily undergo single-component fiber spinning. The chemical, thermal and rheological properties of EVOH were examined herein. Three EVOH copolymers, EV-32, 38 and 44, with different ratios of ethylene to vinyl alcohol (EV ratio), were used to evaluate the influence of the ratio on melt spinnability. The EV ratios of EV-32, EV-38 and EV-44 examined by nuclear magnetic resonance were 0.64, 0.82 and 1.0, respectively. The experimental results reveal that the melting temperature ( Tm) and crystallinity ( Xc) of EVOH decreased in the order EV-32 (178.9℃, 46.6 wt%) > EV-38 (171.9℃, 41.8 wt%) > EV-44 (166.0℃, 40.0 wt%). The thermal stability, however, increases in the order EV-32 < EV-38 < EV-44. The viscosity decreases in the order EV-32 > EV-38 > EV-44. EV-44 has much higher flow activation energy than EV-32 and EV-38, indicating that it has a temperature sensitivity higher than EV-32 and EV-38. The pellets of EV-32, EV-38 and EV-44 were melt spun. Three as-spun fibers, EV-32, EV-38 and EV-44 have cross-sectional diameters of 151.3, 150.9 and 154.1 µm and tensile stresses (strain (%) at breaking point) of 123.1 (205.2%), 121.4 (202.0%) and 131.1 MPa (180.2%), respectively. Most importantly, EV-44 can easily be spun at a relatively low temperature, 245℃, while the other two, EV-38 and EV-32, can hardly be made on condition that the spinning temperatures are higher than 255℃ and 265℃, respectively. Notably, once the spinning temperature of EVOH polymers was higher than 258℃, the degradation of vinyl alcohol segments would cause fuming and broken filaments to eventually terminate the entire spinning process. Ultimately, a brand new fiber, EVOH, with an EV ratio of 1.0, was successfully melt spun and mechanically characterized in this study.
A homogeneous mixture of poly(vinyl alcohol) (PVA), poly(ethylene-co-vinyl alcohol) (EVOH) and multi-walled carbon nanotubes (MWCNTs) was prepared. A nano-enabled composite fiber was continuously spun using this homogeneous mixture through a single-hole spinneret into a coagulation bath containing methanol. The physical properties and the intermolecular interactions of the fiber were studied by scanning electron microscopy, optical microscopy, thermal gravimetric analysis, and infrared spectroscopy. Fourier transform infrared analysis suggests that there is an interfacial interaction between PVA, EVOH, and MWCNT through the functional groups attached to them along the molecular chains of the fibers. Tensile strength was measured. The careful removal of a small amount of PVA produced a 20% increase in tensile strength.
Polycaproamide (PCA) polymer and cationic dyeable polycaproamide (CD-PCA) polymer were blended mechanically in the proportions of 75/25, 50/50, and 25/75 in a melt twin-screw extruder to prepare three PCA/CD-PCA polyblended polymers. Blends of PCA and CD-PCA were spun into filaments. The molar ratio of 5-sodium sulfonate dimethyl isophthalate (5-SSDMI) for CD-PCA polymer was 1.99%. This study investigated the physical properties of PCA/CD-PCA polyblended filaments using gel permeation chromatograph (GPC), nuclear magnetic resonance (NMR), gas chromatography (GC), potentiometer, thermogravimetric analysis (TGA), a rheometer, differential scanning calorimetry (DSC), the density gradient method, wide-angle X-ray diffraction (WAXD), extension stressstrain measurement, and scanning electron microscope (SEM). Flow behavior of PCA/CD-PCA polyblends exhibited positive-deviation blends (PDB), and the 50/50 blend of PCA/CD-PCA showed a maximum value of the melt viscosity. Experimental results of the DSC indicated PCA and CD-PCA molecules easily formed miscible domains. The crystallinities of PCA/CD-PCA polyblended filaments decreased as the 5-SSDMI content increased. Tenacities/densities of PCA/CD-PCA polyblended filaments were also found to decline as the 5-SSDMI content increased. The surface of PCA/CD-PCA polyblended filament exhibited a uniform morphology from the SEM data. PCA and CD-PCA polymers were proved to be a compatible system. The weight loss percentages of the PCA/CD-PCA polyblended filaments increased as the 5-SSDMI content increased in aqueous NaOH solution. The porous morphology of a larger size from 0.01 to 2 m in diameter was observed after alkali treatment of PCA/CD-PCA polyblended filament.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.