scholarly journals Compositions Based on PAN Solutions Containing Polydimethylsiloxane Additives: Morphology, Rheology, and Fiber Spinning

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 815
Author(s):  
Valery G. Kulichikhin ◽  
Ivan Y. Skvortsov ◽  
Lydia A. Varfolomeeva
Keyword(s):  
Phase Separation ◽  
Continuous Medium ◽  
Viscosity Ratio ◽  
Fiber Spinning ◽  
Wet Spinning ◽  
Diffusion Front ◽  
Molecular Weights ◽  
Effect Of Additives ◽  
Coalescence Rate ◽  
Spinning Process

The effect of additives of polydimethylsiloxanes (PDMS) with various molecular weights on the morphology and rheological behavior of polyacrylonitrile (PAN) solutions in dimethyl sulfoxide has been analyzed. It was shown that only partial compatibility of the PDMS with the lowest molecular weight member of the homologous series studied—hexamethyldisiloxane—with PAN solution takes place. All other PDMS samples form emulsions with PAN solutions. The coalescence rate of PDMS drops depends on the viscosity ratio of the disperse phase and the continuous medium, which determines both the duration of dispersion preparation and the conditions for processing emulsions into fibers and films. An anomalous change in viscosity for a series of emulsions with different concentrations of additives, associated with the slippage, was detected. The relaxation properties of emulsions “feel” macro-phase separation. Modeling of the wet spinning process has shown that the morphology of the deposited solution drop reflects the movement of the diffusion front, leading to the gathering droplets in the center of the deposited formulation drop or to their localization in a certain arrangement. It was shown that the emulsion jets upon stretching undergo phase separation.

Effect of the molecular weight and its distribution of polyvinylidene fluoride on the relationship between the spinning process, microstructure and properties of hollow fiber membranes via thermally induced phase separation

2018 ◽  
Vol 89 (7) ◽  
pp. 1311-1320 ◽  
Author(s):  
Nana Li ◽  
Zhe Chang ◽  
Qingchen Lu ◽  
Changfa Xiao ◽  
Junyi Wu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Polyvinylidene Fluoride ◽  
Crystallization Behavior ◽  
Water Flux ◽  
Thermally Induced Phase Separation ◽  
Thermally Induced ◽  
Molecular Weights ◽  
Spinning Process ◽  
The Relationship

Polyvinylidene fluoride (PVDF) is an important material in the preparation of ultrafiltration membranes via the thermally induced phase separation (TIPS) method. In this paper, four PVDF hollow fiber membranes with different molecular weights were prepared via the TIPS method by using dibutyl phthalate and dioctyl phthalate as a mixed diluent. The relationship between the molecular weight of PVDF and its distribution, phase separation, crystallization behavior and spinning process has been systematically studied. The effects of three factors on the microstructure and properties of the PVDF membrane have been analyzed. The flow behaviors of the PVDF/diluent and PVDF melt were tested by a capillary rheometer and a melt flow rate instrument, respectively. A phase diagram of the membrane solution was determined by thermal polarizing microscope and differential scanning calorimetry. The crystallization behavior and angle of orientation of the membrane were tested by using a differential scanning calorimeter and a sound velocity orientation measurement instrument. The microstructures, such as the pore structure and crystalline grain structure, were observed by field emission scanning electron microscopy. Meanwhile, the properties of the membrane were examined from the view of water flux, porosity and tensile testing. The results showed that changes in the polymer molecular weights affected not only the dynamics but also the thermodynamics of phase separation in membrane formation. As the PVDF molecular weight increased, the phase separation region increased, but the membrane structure became denser. A wide molecular weight distribution easily produced large pores. Then, the water flux decreased first and then increased.

scholarly journals New Approach to Preparation of Heat-Resistant “Lola-M” Fiber

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3490 ◽  
Author(s):  
Igor I. Ponomarev ◽  
Ivan Y. Skvortsov ◽  
Yulia A. Volkova ◽  
Ivan I. Ponomarev ◽  
Lydia A. Varfolomeeva ◽  
...  
Keyword(s):  
Energy Efficient ◽  
Ternary Mixture ◽  
Average Diameter ◽  
Fiber Spinning ◽  
Wet Spinning ◽  
New Approach ◽  
Elongation At Break ◽  
Heat Resistant ◽  
Polymer Reaction ◽  
Spinning Process

A new approach to the synthesis of polynaphthoylenebenzimidazoles and heat resistant fiber spinning has been developed using an environmentally friendly and energy efficient method, which operates with solutions of pre-polymers based on 3,3’,4,4’-tetraaminodiphenyl ether and 1,4,5,8-naphthalenetetracarboxylic acid dianhydride in N-methylpyrrolidone. Rheological properties of polymer reaction solutions and appropriate coagulant mixtures were investigated for further wet spinning process. The coagulation process was investigated through microscopic observation of solution droplets which imitate jet/fiber cross section surrounded with coagulants of different composition. For the case of the most optimal viscoelastic properties of dopes the best coagulant was found to be a ternary mixture ethanol/water/NMP (20/10/70). Fibers were prepared through the wet spinning from pre-polymers of various molecular weight characterized by intrinsic viscosity. As a result, complex yarns were spun, and their morphology was characterized and mechanical properties were measured. The strength of ~300 MPa and elastic modulus of ~2 GPa and elongation at break of ~20% were reached for the best fibers at average diameter of ~20 µm. After heat treatment “Lola-M” fibers do not burn and do not support combustion in open flame.

scholarly journals The effect of terminal globular domains on the response of recombinant mini-spidroins to fiber spinning triggers

2020 ◽  
Author(s):  
William Finnigan ◽  
Aled D. Roberts ◽  
Nigel S. Scrutton ◽  
Rainer Breitling ◽  
Jonny J. Blaker ◽  
...  
Keyword(s):  
Spider Silk ◽  
Fiber Spinning ◽  
Fiber Formation ◽  
Wet Spinning ◽  
Salting Out ◽  
Essential Step ◽  
Spinning Process ◽  
Repetitive Protein ◽  
Terminal Domains

AbstractSpider silk spidroins consist of long repetitive protein strands, flanked by globular terminal domains. The globular domains are often omitted in recombinant spidroins, but are thought to be essential for the spiders’ natural spinning process. Mimicking this spinning process could be an essential step towards producing strong synthetic spider silk. Here we describe the production of a range of mini-spidroins with both terminal domains, and characterize their response to a number of biomimetic spinning triggers. Our results suggest that the inclusion of the terminal domains is needed to match the response to shear that native spidroins exhibit. Our results also suggest that a pH drop alone is insufficient to trigger assembly in a wet-spinning process, and must be combined with salting-out for effective fiber formation. With these insights, we applied these assembly triggers for relatively biomimetic wet spinning. This work adds to the foundation of literature for developing improved biomimetic spinning techniques, which ought to result in synthetic silk that more closely approximates the unique properties of native spider silk.

Theoretical and experimental investigation of the wet-spinning process for mechanically strong carbon nanotube fibers

2021 ◽  
Vol 412 ◽  
pp. 128650
Author(s):  
Hyeon Dam Jeong ◽  
Seo Gyun Kim ◽  
Gyeong Min Choi ◽  
Minji Park ◽  
Bon-Cheol Ku ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Carbon Nanotube ◽  
Wet Spinning ◽  
Spinning Process ◽  
Carbon Nanotube Fibers

scholarly journals Hierarchical spidroin micellar nanoparticles as the fundamental precursors of spider silks

2018 ◽  
Vol 115 (45) ◽  
pp. 11507-11512 ◽  
Author(s):  
Lucas R. Parent ◽  
David Onofrei ◽  
Dian Xu ◽  
Dillan Stengel ◽  
John D. Roehling ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Spider Silk ◽  
Fiber Spinning ◽  
Fiber Formation ◽  
Natural Material ◽  
Physical Form ◽  
Spinning Process ◽  
Black Widow Spiders ◽  
Spider Silks

Many natural silks produced by spiders and insects are unique materials in their exceptional toughness and tensile strength, while being lightweight and biodegradable–properties that are currently unparalleled in synthetic materials. Myriad approaches have been attempted to prepare artificial silks from recombinant spider silk spidroins but have each failed to achieve the advantageous properties of the natural material. This is because of an incomplete understanding of the in vivo spidroin-to-fiber spinning process and, particularly, because of a lack of knowledge of the true morphological nature of spidroin nanostructures in the precursor dope solution and the mechanisms by which these nanostructures transform into micrometer-scale silk fibers. Herein we determine the physical form of the natural spidroin precursor nanostructures stored within spider glands that seed the formation of their silks and reveal the fundamental structural transformations that occur during the initial stages of extrusion en route to fiber formation. Using a combination of solution phase diffusion NMR and cryogenic transmission electron microscopy (cryo-TEM), we reveal direct evidence that the concentrated spidroin proteins are stored in the silk glands of black widow spiders as complex, hierarchical nanoassemblies (∼300 nm diameter) that are composed of micellar subdomains, substructures that themselves are engaged in the initial nanoscale transformations that occur in response to shear. We find that the established micelle theory of silk fiber precursor storage is incomplete and that the first steps toward liquid crystalline organization during silk spinning involve the fibrillization of nanoscale hierarchical micelle subdomains.

scholarly journals Water vapor induced self-assembly of islands/honeycomb structure by secondary phase separation in polystyrene solution with bimodal molecular weight distribution

2021 ◽  
Author(s):  
Maciej Łojkowski ◽  
Adrian Chlanda ◽  
Emilia Choińska ◽  
Wojciech Swieszkowski
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Self Assembly ◽  
Secondary Phase ◽  
Honeycomb Structure ◽  
Polymer Chains ◽  
Molecular Weights ◽  
Secondary Phase Separation

<p>The formation of complex structures in thin films is of interest in many fields. Segregation of polymer chains of different molecular weights is a well-known process. However, here, polystyrene with bimodal molecular weight distribution, but no additional chemical modification was used. It was proven that at certain conditions, the phase separation occurred between two fractions of bimodal polystyrene/methyl ethyl ketone solution. The films were prepared by spin-coating, and the segregation between polystyrene phases was investigated by force spectroscopy. Next, water vapour induced secondary phase separation was investigated. The introduction of moist airflow induced the self-assembly of the lower molecular weight into islands and the heavier fraction into a honeycomb. As a result, an easy, fast, and effective method of obtaining island/honeycomb morphologies was demonstrated. The possible mechanisms of the formation of such structures were discussed.</p>

Tough synthetic spider-silk fibers obtained by titanium dioxide incorporation and formaldehyde cross-linking in a simple wet-spinning process

Biochimie ◽  
2020 ◽  
Vol 175 ◽  
pp. 77-84
Author(s):  
Hongnian Zhu ◽  
Yuan Sun ◽  
Tuo Yi ◽  
Suyang Wang ◽  
Junpeng Mi ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Spider Silk ◽  
Wet Spinning ◽  
Cross Linking ◽  
Silk Fibers ◽  
Spinning Process
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