This study examined the spinning of polyurethane-based elastomeric fibers with the dry-jet-wet spinning method. The three important spinning variables that were chosen were the coagulation bath ratio (dimethylformamide/water), the bath temperature, and the stretch ratio. A three-variable factorial design method, proposed by Box and Behnken, was used to optimize these process parameters. The spinning process was further fine-tuned by the variation of the stretch ratio and the dope solid content. The effect of the dry-jet length on the fiber properties was also studied. The tenacity and elastic recovery properties of the fibers were found to be optimum at a bath ratio (dimethylformamide/water) of 60 : 40, a bath temperature of 15 C, and a stretch ratio of 2.5. The density and sonic modulus were measured to determine the effect of varying the process variables on structural parameters such as the density and orientation. The surface morphological features, as revealed by scanning electron microscopy, were correlated to the fiber properties.
Polyurethane/clay nanocomposite (PUCN) filaments were spun by the dry‐jet‐wet spinning method. To prepare the PUCN filaments, 0.25, 0.50 and 1% of nanoclay on the weight of polyurethane were incorporated in the polyurethane dope. The interaction between clay and polyurethane was analysed by attenuated total reflectance–Fourier Transform‐infrared (ATR‐FTIR) spectroscopy. The structure and morphology of the PUCN filaments were analysed by wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). Both the neat polyurethane and the PUCN filaments were dyed with different acid, basic and reactive dyes. The neat polyurethane filaments exhibited poor dyeability with all three classes of dyes. By contrast, the PUCN filaments showed a significantly higher dye uptake with all of the dyes used. Furthermore, the dye uptake increased significantly as the percentage of clay in the filaments increased, as indicated by the increase in the K/S values of the dyed filaments. The dyeing mechanism with all three dyes, as well as the increased dyeability of the PUNC filaments in comparison to those of the neat polyurethane filaments, was discussed.
This article reports a study on the spinnability of three different ester type thermoplastic polyurethanes (TPUs) with shore hardness 75A, 85A, 92A using the dry-jet-wet spinning method. The three grades have been analyzed by FTIR, GPC, and 1 H-NMR to establish the difference among them. FTIR indicated that all the three grades were chemically similar and GPC suggests that molecular weight increased with increase in shore hardness. Compositional analysis indicates that the hard segment content increases with increase in shore hardness. Shear viscosity of TPU dope solution increases with increase in shore hardness. Of the three different grades of TPUs studied, only the grades with shore hardness of 85A and 92A are spinnable under the experimental conditions. The fiber properties of three different grades have been compared. Fibers spun with the shore hardness of 85A have good elastomeric properties compared with the other two grades. Lab spun fibers have also been compared with the commercial spandex fibers. V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 843-851, 2010
This paper reports a study on liquid-liquid phase separation in an isothermal ternary system of segmented polyurethane/dimethylformamide/water system with and without the presence of nanoclay dispersion in the system. Isothermal ternary phase diagrams for three different grades with varying shore A hardness of thermoplastic polyurethane (TPU)/solvent/nonsolvent system were constructed based on the cloud point measurement that was carried out by the titration method. The effect of temperature on phase diagrams has also been studied. The binary interaction parameters between TPUs and water were estimated by water sorption experiments. The effect of organoclay dispersion concentration in the TPU solution on isothermal ternary phase diagrams has also been studied. This understanding of phase separation characteristics would be very helpful in correlating the final morphology developed in wet-spun TPU as well as polyurethane/clay nanocomposite fibres.
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