We report on the pilot scale synthesis and melt spinning of poly(ethylene furanoate) (PEF), a promising bio-based fiber polymer that can heave mechanical properties in the range of commercial poly(ethylene terephthalate) (PET) fibers. Catalyst optimization and solid state polycondensation (SSP) allowed for intrinsic viscosities of PEF of up to 0.85 dLꞏg−1. Melt-spun multifilament yarns reached a tensile strength of up to 65 cN.tex−1 with an elongation of 6% and a modulus of 1370 cN.tex−1. The crystallization behavior of PEF was investigated by differential scanning calorimetry (DSC) and XRD after each process step, i.e., after polymerization, SSP, melt spinning, drawing, and recycling. After SSP, the previously amorphous polymer showed a crystallinity of 47%, which was in accordance with literature. The corresponding XRD diffractograms showed signals attributable to α-PEF. Additional, clearly assignable signals at 2θ > 30° are discussed. A completely amorphous structure was observed by XRD for as-spun yarns, while a crystalline phase was detected on drawn yarns; however, it was less pronounced than for the granules and independent of the winding speed.
The idea of ”Nanoval technology“ origins in the metal injection molding for gas atomization of metal powders and the knowledge of spunbond technologies for the creation of thermoplastic nonwovens using the benefits of both techniques. In this study, we evaluated processing limits experimentally for the spinning of different types of polypropylene, further standard polymers, and polyphenylene sulfide, marked by defect-free fiber creation. A numerical simulation study of the turbulent air flow as well as filament motion in the process visualized that the turnover from uniaxial flow (initial stretching caused by the high air velocity directed at the spinning die) to turbulent viscoelastic behavior occurs significantly earlier than in the melt-blown process. Modeling of the whole process showed that additional guide plates below the spinneret reduce the turbulent air flow significantly by regulating the inflow of secondary process air. The corresponding melt flow index of processible polymer grades varied between 35 g·10min−1 up to 1200 g·10min−1 and thus covering the range of extrusion-type, spunbond-type, yarn-type, and meltblown-type polymers. Hence, mean fiber diameters were adjustable for PP between 0.8 and 39.3 μm without changing components of the process setup. This implies that the Nanoval process enables the flexibility to produce fiber diameters in the typical range achievable by the standard meltblown process (~1–7 μm) as well as in the coarseness of spunbond nonwovens (15–30 μm) and, moreover, operates in the gap between them.
An experimental setup used to measure the bending stiffness of polymer filaments based on existing cantilever approaches is presented. Additionally, it is utilized to evaluate the influence of molar mass and long-chain branching on filaments of poly(butylene terephthalate), modified with a multifunctional chain extender. Using shear rheological analysis process limits for extrusion of the modified material were revealed, indicated by a change of the curve shape of van Gurp-Palmen plots. For the processable modified materials, it was found that increasing molar mass and degree of long-chain branching, caused by the modification, raise the bending stiffness of filaments. Also the Young's modulus was found to increase with the amount of chain extender used, while no difference could be generated by using different linear molar grades of the polymer.
Um eine Basis für eine nachhaltigere Polymer- und Textilindustrie zu schaffen, sollen biobasierte Polymere, wie PEF (Polyethylenfuranoat) die bekannten erdölbasierten Kunststoffe künftig so weit wie möglich ersetzen können. Anwendungen liegen dabei z.B. in biobasierten Fasern für Bekleidung und technische Textilien, aber auch in Hochleistungsfasern, wie sie für Reifencord-Garne benötigt werden. Im Projekt PFIFFIG (Polymer-FIbers From bio-based Furanoates targeting Industrial Grade) forschen mehrere Institute und Industriepartner entlang der Wertschöpfungskette von PEF vom Pflanzenrohstoff bis zur technischen Endanwendung. An den DITF gelang dabei die Synthese und Ausspinnung von PEF zu Garnen, die die Anforderungen für textile, aber auch für Hochfestigkeitsanwendungen erfüllen.
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