Melt Spinning Of Poly Research Articles

Production and Characterization of Melt-Spun Poly(3-hydroxybutyrate)/Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Blend Monofilaments.

We investigated the melt-spinning potential of a poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blend using a piston spinning machine with two different spinneret diameters (0.2 and 0.5 mm). Results from the differential scanning calorimetry, dynamic mechanical thermal analysis, and tensile testing showed distinct filament properties depending on the monofilaments' cross-sectional area. Finer filaments possessed different melting behaviors compared to the coarser filaments and the neat polymer, indicating the formation of a different type of polymer crystal. Additionally, the mechanical properties of the finer filament (tensile strength: 21.5 MPa and elongation at break: 341%) differed markedly from the coarser filament (tensile strength: 11.7 MPa, elongation at break: 12.3%). The hydrolytic stability of the filaments was evaluated for 7 weeks in a phosphate-buffered saline solution and showed a considerably reduced elongation at break of the thinner filaments. Overall, the results indicate considerable potential for further filament improvements to facilitate textile processing.

Poly(Ethylene Furanoate) along Its Life-Cycle from a Polycondensation Approach to High-Performance Yarn and Its Recyclate.

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 dL·g−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.

Elaborating Mechanisms behind the Durability of Tough Polylactide Monofilaments under Elevated Temperature and Humidity Conditions

Melt-spun poly(l-lactic acid) (PLA) monofilaments with excellent toughness have been subjected to environmental weathering under varying temperatures in the range of 50–70 °C, that is, below and close to the glass transition temperature Tg, and at 20–95% relative humidity in order to follow the evolution of their mechanical performance. Environmentally triggered structural changes and the hydrolytic degradation of the monofilaments have been evaluated by analysis of their thermal and mechanical properties as well as their long-term relaxation behavior using a self-developed model. Despite structural changes, the fibers demonstrate a long-term preservation of the toughness under environmental conditions of physical aging. The mechanisms behind the observed durability of the PLA material are attributed to the relaxation of the confined amorphous phase presumably as a result of the local chain scission. Conditions when hydrolytic degradation leads to mechanical failure correspond to an absolute humidity of 90 g/m3 independent of the temperature of the aging. Presented results reveal a persistence of the mechanical performance of PLA fibers upon aging under moderate conditions, thus offering possible design strategies toward tough and durable PLA materials for sustainable technologies.

Melt-Spun Poly(D,L-lactic acid) Monofilaments Containing N,N-Diethyl-3-methylbenzamide as Mosquito Repellent.

Malaria is still a major tropical disease, with Africa particularly burdened. It has been proposed that outdoor protection could aid substantially in reducing the malaria incidence rate in rural African communities. Recently, melt-spun polyolefin fibers containing mosquito repellents have been shown to be promising materials to this end. In this study, the incorporation of N,N‑Diethyl‑3‑methylbenzamide (DEET)—a popular and widely available mosquito repellent—in commercially available, amorphous poly(D,L-lactic acid) (PDLLA) is investigated with the aim of producing biodegradable mosquito-repelling filaments with a reduced environmental impact. It is shown to be possible to produce macroscopically stable PDLLA-DEET compounds containing up to 20 wt.-% DEET that can be melt-spun to produce filaments, albeit at relatively low take-up speeds. A critical DEET content allows for stress-induced crystallization during the spinning of the otherwise amorphous PDLLA, resulting in the formation of α-crystals. Although the mechanical integrity of the filaments is notably impacted by the incorporation of DEET, these filaments show potential as materials that can be used for Malaria vector control.

Fabrication of piezoelectric poly(l-lactic acid)/BaTiO3 fibre by the melt-spinning process

Poly(l-lactic acid) (PLLA) based piezoelectric polymers are gradually becoming the substitute for the conventional piezoelectric ceramic and polymeric materials due to their low cost and biodegradable, non-toxic, piezoelectric and non-pyroelectric nature. To improve the piezoelectric properties of melt-spun poly(l-lactic acid) (PLLA)/BaTiO3, we optimized the post-processing conditions to increase the proportion of the β crystalline phase. The α → β phase transition behaviour was determined by two-dimensional wide-angle x-ray diffraction and differential scanning calorimetry. The piezoelectric properties of PLLA/BaTiO3 fibres were characterised in their yarn and textile form through a tapping method. From these results, we confirmed that the crystalline phase transition of PLLA/BaTiO3 fibres was significantly enhanced under the optimised post-processing conditions at a draw ratio of 3 and temperature of 120 °C during the melt-spinning process. The results indicated that PLLA/BaTiO3 fibres could be a one of the material for organic-based piezoelectric sensors for application in textile-based wearable piezoelectric devices.

Properties, X-ray data and 2D WAXD fitting procedures of melt-spun poly(ɛ-caprolactone).

Rheological and thermal properties of the poly(ɛ-caprolactone) (PCL) polymer are presented in Section 1.1. Section 1.2 summarizes results of melt-spun PCL filaments. Specifically, we show the necking point stabilization during high-speed online drawing in Section 1.2.1, filament morphology in Section 1.2.2, wide-angle X-ray diffraction (WAXD) fitting results in Section 1.2.3, WAXD patterns of aged fibers in Section 1.2.4, crystallinity analysis in Section 1.2.5 and small-angle X-ray scattering (SAXS) analysis results in Section 1.2.6. Details about the materials, experimental and analytical methods are given in Section 2. Of particular interest may be the simulation and fitting procedures of 2D WAXD patterns, which are summarized in Section 2.7.2. For more information see the publication by Selli et al. 'Mesophase in melt-spun poly(ɛ-caprolactone) filaments: structure–mechanical property relationship' [1].

Mesophase in melt-spun poly(ϵ-caprolactone) filaments: Structure–mechanical property relationship

Fine poly(ϵ-caprolactone) (PCL) filaments (diameter: 59–92 μm) were successfully melt-spun with modified drawing setups to prevent draw instabilities. Depending on the production parameters, different mechanical properties were obtained (tensile strength: 302–456 MPa, elongation at break: 69–88%). These variations are related to subtle structural differences, which we have analyzed with wide-angle x-ray diffraction (WAXD) and small-angle x-ray scattering (SAXS). SAXS was used to determine crystal widths and the spacing between crystals along the filament axis. Additionally, 2D WAXD patterns were simulated and WAXD profiles were fitted. The detailed 2D WAXD analysis revealed that a highly-oriented non-crystalline mesophase is present in drawn PCL filaments, which is most-likely situated in-between PCL crystals. A large amount of this mesophase (>16%), combined with high crystalline orientation and perfect crystals, led to higher tensile strength values. We also confirmed that PCL chains pack with non-planar chain conformations in the unit cell.

Structural response of melt-spun poly(3-hydroxybutyrate) fibers to stress and temperature

We have investigated the structural response of melt-spun poly-3-hydroxybutyrate (P3HB) fibers to stress and temperature and its impact on the mechanical properties. Low-stress (≤1.6 MPa, 100–130 °C) annealed P3HB fibers showed a considerable viscoelastic behavior and remained ductile up to at least two months. Stress annealing with high weights (≥32 MPa), however, lead to fibers with a higher tensile strength (182 MPa) and with a lower elongation at break (22%). These significant differences in the tensile properties are closely related to structural changes, which we have studied with in-situ wide-angle x-ray diffraction (WAXD) and small-angle x-ray scattering (SAXS) experiments. A highly oriented non-crystalline mesophase (Pnc), which is located in-between orthorhombic α-crystals is growing during high-stress annealing but disappears during low-stress annealing. However, it is possible to restore the mesophase by post-drawing. The viscoelastic hysteresis behavior of low-stress annealed fibers is explained by a reversible transformation of α-crystals into mesophase and back.

Fabrication, characterization and modelling of triple hierarchic PET/CB/TPU composite fibres for strain sensing

In this study, a triple-layered coaxial fibre structure was fabricated for strain sensor applications. The core consisted of melt-spun poly (ethylene terephthalate) (PET) where in a subsequent step carbon black (CB) particles were coated onto the surface of the PET fibre to build the conductive pathways by a dissolving-coating method. For the outer protective sheath, a thermoplastic polyurethane (TPU) with a thickness of about 7 μm was generated using a layer-by-layer assembly technique. Compared with other investigated CB-coated fibres, the novel triple hierarchic PET/CB/TPU composite fibres exhibit a high Young’s modulus and tensile strength, as well as a doubled sensing range. The fabrication process can be directly used in the textile industry for the production of wearable and flexible sensors due to its efficacy and low cost. Moreover, a model based on tunnelling theory utilizing only two adjustable parameters was modified based on the actual experimental data, which could precisely describe the relative change of resistance upon the applied strain. Meanwhile, an empirical equation was first proposed and this model offers an effective but simple approach towards quantitative analysis of strain sensors.

Effect of Polycondensation Catalyst on Fiber Structure Development in High-Speed Melt Spinning of Poly (Ethylene Terephthalate).

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.

Rheological Behaviors and Properties of Poly (Ether Ether Ketone) In-Situ Blends: Effect of Chemical Structure of Added Thermotropic Liquid Crystalline Polyarylates

Two kinds of thermotropic liquid crystalline polyesters (TLCP) with different chemical structures were used as flow modifiers during the melt spinning of poly (ether ether ketone). One of TLCPs, named PAT-S, was a kind of aromatic polyester synthesized from 4-acetoxybenzoicacid and 6-hydroxy-naphthoic acid, and the other one named, PEEKAR, was a block copolymer based on poly (ether ether ketene) (PEEK) oligomers and PAT-S oligomers. The effects of the chemical structures of the prepared TLCPs on the rheological behavior of the TLCP/PEEK blends were measured by rheological measurements, and then the structure and properties of the TLCP/PEEK in-situ blend fibers were studied by a series of methods, including differential scanning calorimetry (DSC), wide angle X-ray diffraction (WRXD), optical microscopy (OM), scanning electron microscopy (SEM), orientation degree tests, mechanical properties tests, etc. The results showed that the melt viscosity of PEEK could be effectively reduced by nearly 20% by adding a small amount of PEEKAR or PAT-S with the viscosity reducing effect of PEEKAR on PEEK being greater than that of PAT-S; this was mainly caused by the better compatibility between PEEK and PEEKAR because of the similar segment structures. The crystallinity of the PEEK fibers increased by nearly 50% with addition of both TLCPs, indicating that both the PEEKAR and PAT-S could serve as nucleating agent as well. The results from the morphology analysis clearly proved that PEEKAR had a better compatibility with the PEEK resin compared with PAT-S. The tensile strength of the PEEK fibers could be improved to some extent by adding PEEKAR, while it was obviously reduced after adding PAT-S.

Tensile study of melt-spun poly(3-hydroxybutyrate) P3HB fibers: Reversible transformation of a highly oriented phase

Poly-3-hydroxybutyrate (P3HB) typically crystallizes into the orthorhombic α-form. The additional intense and rather broad equatorial reflection in wide-angle X-ray diffraction (WAXD) patterns seen in our melt-spun P3HB fibers cannot be attributed to the α-form crystals. We propose that a non-crystalline mesophase, which consists of disordered but highly oriented and stretched molecules located between α-crystals, leads to the observed broad equatorial reflection. We show that the transformation of this mesophase from and into the α-form phase is partially reversible under cyclic tensile loading. Structure factor calculations, which are based on atomic positions from molecular dynamics simulations of a set of stretched P3HB molecules, support this model. The WAXD patterns were analyzed with azimuthal, radial, equatorial and meridional scans and the changes in the crystal orientation, changes in the percentages of individual phases and changes in the α-crystal lattice spacings were analyzed as a function of the applied tension. Changes in long spacings, crystal sizes and coherence lengths under cyclic loading were determined with small-angle X-ray scattering (SAXS) measurements. The long spacing between α-crystals increases when tensile stress is applied and it snaps back to the original spacing when the tensile stress is released.

The effect of gamma-irradiation on morphology and properties of melt-spun poly (lactic acid)/cellulose fibers

The effect of gamma irradiation on both morphology and properties of neat poly(lactic acid) (PLA), PLA/microcrystalline cellulose (MCC) and PLA/cellulose nanowhiskers (CNW) fibers loaded at 1 wt% filler content was investigated in presence of PLA-grafted maleic anhydride (PLA-g-MA) used as the compatibilizer. Multifilament yarns were prepared by a melt-spinning process and subjected to gamma irradiation at various doses from 5 to 30 kGy keeping the dose rate at 1.92 kGy/h under ambient conditions. Chemical structure, morphology and property changes induced by gamma irradiation on the samples were evaluated by several techniques considering the filler aspect ratio effect. The results showed a dose-related increase in the scission index (SI) of the irradiated samples whatever the filler size, while thermal and tensile properties significantly decreased. However, the incorporation of cellulosic fillers in PLA fibers, in particular MCC, was found to hinder the radiolytic degradation process of the irradiated samples.

Structural response of melt-spun poly(3-hydroxybutyrate) fibers to heat and stress investigated by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS)

Structural response of melt-spun poly(3-hydroxybutyrate) fibers to heat and stress investigated by wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS)

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

The influence of solid-state drawing on the morphology of melt-spun poly(l-lactic acid) (PLLA) tapes, and the accompanying changes in mechanical and degradation behaviour have been studied. Mechanical properties are found to be strongly dependent on both applied draw ratio and drawing temperature. Moduli of these highly oriented tapes are significantly increased compared to as-extruded tapes at both ambient and elevated temperatures. Interestingly, drawing leads to a significant increase in elongation to break (~3 times) and toughness (~13 times) compared to as-extruded tapes. Structural and morphological characterization indicates strain-induced crystallization as well as an increase in orientation of the crystalline phase at small strains. Upon further stretching, an “overdrawing” regime is observed, with decreased crystalline orientation due to the breakage of existing crystals. For fixed draw ratios, a significant increase in Young’s modulus and tensile strength is observed with increasing drawing temperature, due to a higher crystallinity and orientation obtained for tapes drawn at higher temperatures. FT-IR results indicate no crystal transformation after drawing, with the α-form being observed in all tapes. Hydrolytic degradability of PLLA was significantly reduced by solid-state drawing.

Molecular orientation in melt-spun poly(3-hydroxybutyrate) fibers: Effect of additives, drawing and stress-annealing

Bacterial poly-3-hydroxybutyrate (P3HB) is a thermoplastic polyester with perfectly isotactic structure; it has the potential of being melt-spun to fibers, and it is thus interesting for textile applications. Aiming at developing an upscalable melt-spinning method to produce high-strength fibers, we have investigated P3HB as native polymer with the additives tri-n-butyl citrate (TBC) as plasticizer, and boron nitride (BN) as nucleating agent, to evaluate their effect on the melt-spinning performance of P3HB. In addition, the draw-off unit has been modified in order to enhance primary crystallization to the extent that secondary crystallization is suppressed. The such drawn fibers are dominated by longitudinally oriented lamellae rather than spherulitic structures. This allows obtaining P3HB fibers which contain domains of highly oriented molecules between crystallites, exhibiting promising tensile strengths up to 215MPa. The wide-angle X-ray diffraction (WAXD) data suggest that besides the oriented crystalline α-phase, a highly oriented amorphous phase is present.

Production and characterization of melt-spun Poly(Ether Ether Ketone) fibers for biomedical applications

Melt-spun Poly (Ether Ether Ketone) (PEEK) fibers were produced on a custom built melt-spinning system. Fibers of two different grades were spun at two different draw-down ratios, with one of three possible post-spinning treatments: as-spun, annealed, or hot drawn. Fibers were characterized with SEM, DSC, WAXS, and tensile testing. Hot drawn fibers had the highest degree of crystalline orientation (S = 0.81). Modulus, strength, and yield stress, were found to be 1.7 GPa, 175 MPa, and 45 MPa, respectively for as-spun fibers. As-spun fibers had strains-to-failure as high as 215%, which decreased to about 25% after hot drawing. Annealed and drawn fibers had similar crystallinity and crystalline orientation, but drawn fibers had significantly higher moduli of 2.8 GPa and 5.2 GPa, and strength of 195 MPa and 480 MPa, respectively. Fiber properties were found to be tunable to a number of combinations, with potential for numerous applications as novel biomaterials.

Melt Spinning of Poly(lactic acid) and Hydroxyapatite Composite Fibers: Influence of the Filler Content on the Fiber Properties

Composite fibers from poly(lactic acid) (PLA) and hydroxyapatite (HA) particles were prepared using melt spinning. Different loading concentrations of HA particles (i.e., 5, 10, 15, and 20 wt %) in the PLA fibers and solid-state draw ratios (SSDRs) were evaluated in order to investigate their influence on the fibers' morphology and thermal and mechanical properties. A scanning electron microscopy investigation indicated that the HA particles were homogeneously distributed in the PLA fibers. It was also revealed by atomic force microscopy and Fourier transform infrared spectroscopy that HA particles were located on the fiber surface, which is of importance for their intended application in biomedical textiles. Our results also suggest that the mechanical properties were independent of the loading concentration of the HA particles and that the SSDR played an important role in improving the mechanical properties of the composite fibers.

The effect of process variables on the properties of melt-spun poly(lactic acid) fibres for potential use as scaffold matrix materials

Biodegradable materials in the form of fibres and yarns have attracted increasing attention due to a large surface area and various geometric possibilities in three-dimensional polymeric scaffolds for tissue engineering applications. In this study, poly(lactic acid) fibres were produced by melt spinning and subsequent solid-state drawing in order to serve as matrix materials for fibre-based scaffold architectures. The processing of both monofilament and multifilament fibres as well as draw ratios and temperatures were investigated to analyze the effect of process variables on the properties. Two different polylactides with different molecular weight were studied and characterized in terms of their tensile and thermal properties and morphology. The relevance of fibre formation, solid-state drawing and drawing temperatures was clearly supported by the results, and it was shown that the physical properties, such as crystallinity, mechanical strength and ductility can be controlled largely by the drawing process. The obtained fibres demonstrated great potential to be further processed into biotextiles (woven, knitted, or nonwoven scaffolds) using the textile technologies.

CFD modeling of the melt spinning of poly (ethylene terepthalate) at low take-up velocities

In this study, a model was formulated to describe the melt spinning of Poly (ethylene terepthalate) (PET) at different quench air speeds and temperatures, mass throughputs and a low range of take-up velocities. The constitutive equations of the Newtonian model were used for modeling, which assumed the flow of polymer was viscous. To simulate the influence of the process parameters on the melt spinning process, a fiber model was used and coupled with computational fluid dynamics (CFD) calculations of the quench air flow. In the fiber model, energy, momentum and mass balance were solved for the polymer mass flow. The formulation was implemented in the Fluent Continuous Fiber Model. Numerical predictions of the model were compared with experimental data reported in the literature for PET. The take up speed, mass throughput and the temperature of melt spinning were the primary parameters of final fiber properties for both simulation and experimental results. In the simulation results, the effects of take-up speed and mass throughputs were clearly different at high take-up velocities and low mass throughputs because of viscoelastic behavior of polymers in the melt spinning. The Newtonian model was more reasonable for lower take-up speeds and higher mass throughputs. Key words: Melt spinning, poly (ethylene terepthalate), modeling, process parameters.