Polytetrafluoroethylene Paste Extrusion: A Fibrillation Model and Its Relation to Mechanical Properties

Ardakani, Hesam Anvari; Mitsoulis, Evan; Hatzikiriakos, Savvas G.

doi:10.3139/217.2744

Cited by 15 publications

(5 citation statements)

References 14 publications

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“…3 a: in region I, the stress grows rapidly, in region II it remains relatively stable at strains from 50 % to 250 % which is called the plateau region 30, and in region III it slowly declined with increasing strain. A similar stress‐stain curve was also reported by Ardakani et al 31. It has been confirmed by a mechanical model that the tensile change is due to elastic deformation and plastic deformation during stretching 30, 32.…”

Section: Resultssupporting

confidence: 88%

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Effect of Stretching Parameters on Structure and Properties of Polytetrafluoroethylene Hollow‐Fiber Membranes

2016

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Polytetrafluoroethylene (PTFE) porous hollow-fiber membranes were prepared by a method involving billet preform, paste extrusion, stretching, and sintering. The influence of stretching parameters including stretching ratio, temperature, and speed was systematically investigated. The structure and properties of these membranes were characterized by field emission scanning electron microscopy, filtration performance, and mechanical strength test. The results indicate that the stretching ratio is the most significant influencing factor for the formation of various regions in the stress-strain curve. With increasing stretching ratio, the porosity, maximum pore size, and ethanol flux increase remarkably while bovine serum albumin rejection is reduced. These findings have the potential to facilitate PTFE membrane fabrication with finely tuned microporous structure for various application processes.

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Section: Resultssupporting

confidence: 88%

“…It is generally known that PTFE is a hydrophobic material with a water contact angle of 108° 31, 38. With the increase of the stretching ratio from 0 to 3.0, the water contact angles also enlarge from 107° to 122°.…”

Section: Resultsmentioning

confidence: 99%

Effect of Stretching Parameters on Structure and Properties of Polytetrafluoroethylene Hollow‐Fiber Membranes

2016

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“…The procedure we chose to prepare our membranes (see Section 2.2) consists of promoting fibrillation of the PTFE resin particles, which are, on average, 1-2 µm in diameter, to ensure their cohesion. These are the fibers that appear in some of the SEM images in Figure 5a, and are even clearer in Figure 8, adapted from the work of Ardakani et al [53]. The appearance of these fibers and the mechanical compression during the shaping of the membranes considerably reduced the free interstices for the passage of the different molecules, such as water molecules.…”

Section: Determination Of Pore Diametersmentioning

confidence: 80%

Synthesis and Evaluation of Asymmetric Mesoporous PTFE/Clay Composite Membranes for Textile Wastewater Treatment

et al. 2021

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Asymmetric mesoporous composite PTFE membranes wit 40, 50, and 85 wt.% of a clay (kaolin) were fabricated and characterized using a scanning electron microscope equipped with EDX for morphology and elemental analysis. The surface chemistry of the membranes was checked using Fourier transform infrared spectroscopy. The effect of incorporating the clay on the hydrophilicity, permeability, morphology, and antifouling properties of the fabricated membranes was investigated. It was observed that incorporating kaolin particles improved the mechanical properties but decreased the contact angle of the membranes, thereby resulting in an improvement in the membrane permeability. The performance of the three composite UF membranes was evaluated through the treatment of a real textile effluent sample containing indigo dye. The results confirmed that these membranes are effective in the removal of COD, color, and turbidity. Indeed, at a transmembrane pressure of 2.5 bar, almost total removal of the turbidity, COD removal > 85%, and color removal > 97% were attained. Furthermore, membrane A85 (with 85% clay) showed the best performance, with a water flux of 659.1 L·h−1·m−2·bar−1. This study highlights the potential of incorporating low-cost clay material for the enhancement of the performance of mixed organic/inorganic matrix membranes, which can be applied to textile wastewater treatment.

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“…During extrusion, crystallites at the PTFE surface became interlocked, and then as the particles continued to slide past one another, the crystallites "unwound" to form long fibrils. Fibrillation of PTFE only powders has also been suggested to require a combination of compression and shear deformation (Ardakani et al, 2013).…”

Section: Microstructurementioning

confidence: 99%

Solvent-free NMC electrodes for Li-ion batteries: unravelling the microstructure and formation of the PTFE nano-fibril network

Matthews,

Wheeler,

Ramírez-González

et al. 2024

Front. Energy Res.

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The microstructure and electrochemical performance of solvent-free processed and slurry cast Li(Ni0.6Co0.2Mn0.2)O2 (NMC622) based electrodes for Li-ion batteries has been investigated. In contrast to a moss-like PVDF-based carbon binder domain in slurry cast electrodes, the PTFE binder in solvent-free electrodes had a hierarchical morphology composed of primary fibrils of a few µm in diameter and 100’s µm in length that branched into secondary and then ever finer fibrils, down to diameters of 10s nm or below. A mechanism for the formation of the branch-like morphology observed in PTFE-based solvent-free electrodes is also presented. Even the finest fibrils were confirmed to survive typical cathode cycling conditions. The solvent-free electrodes showed progressive improvement in capacity with increasing charge-discharge rate (up to 150% at 2C) compared with slurry cast equivalents. The capacity of solvent-free electrodes faded 40% slower over 200 cycles at C/3. Impedance analysis showed the solvent-free microstructure enabled reduced charge transfer resistance and ionic resistance, arising from minimal obscuration of the active material surface and no pore blockage.

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Polytetrafluoroethylene Paste Extrusion: A Fibrillation Model and Its Relation to Mechanical Properties

Cited by 15 publications

References 14 publications

Effect of Stretching Parameters on Structure and Properties of Polytetrafluoroethylene Hollow‐Fiber Membranes

Effect of Stretching Parameters on Structure and Properties of Polytetrafluoroethylene Hollow‐Fiber Membranes

Synthesis and Evaluation of Asymmetric Mesoporous PTFE/Clay Composite Membranes for Textile Wastewater Treatment

Solvent-free NMC electrodes for Li-ion batteries: unravelling the microstructure and formation of the PTFE nano-fibril network

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