scholarly journals Shear Force Fiber Spinning: Process Parameter and Polymer Solution Property Considerations

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 294 ◽  
Author(s):  
Arzan Dotivala ◽  
Kavya Puthuveetil ◽  
Christina Tang

For application of polymer nanofibers (e.g., sensors, and scaffolds to study cell behavior) it is important to control the spatial orientation of the fibers. We compare the ability to align and pattern fibers using shear force fiber spinning, i.e. contacting a drop of polymer solution with a rotating collector to mechanically draw a fiber, with electrospinning onto a rotating drum. Using polystyrene as a model system, we observe that the fiber spacing using shear force fiber spinning was more uniform than electrospinning with the rotating drum with relative standard deviations of 18% and 39%, respectively. Importantly, the approaches are complementary as the fiber spacing achieved using electrospinning with the rotating drum was ~10 microns while fiber spacing achieved using shear force fiber spinning was ~250 microns. To expand to additional polymer systems, we use polymer entanglement and capillary number. Solution properties that favor large capillary numbers (>50) prevent droplet breakup to facilitate fiber formation. Draw-down ratio was useful for determining appropriate process conditions (flow rate, rotational speed of the collector) to achieve continuous formation of fibers. These rules of thumb for considering the polymer solution properties and process parameters are expected to expand use of this platform for creating hierarchical structures of multiple fiber layers for cell scaffolds and additional applications.

2018 ◽  
Vol 115 (45) ◽  
pp. 11507-11512 ◽  
Author(s):  
Lucas R. Parent ◽  
David Onofrei ◽  
Dian Xu ◽  
Dillan Stengel ◽  
John D. Roehling ◽  
...  

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.


2021 ◽  
pp. 33-33
Author(s):  
Yan-Ping Liu ◽  
Chun-Chun Wang ◽  
Shi-Jie Li

The Langmuir kinetic equation is analyzed by the variational iteration method, its solution property is revealed analytically. The effects of desorption time and adsorption coefficient on the solution properties are also discussed, and a fractal modification of Langmuir kinetic equation is suggested.


2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Alok Dhungana ◽  
Prabir Basu ◽  
Animesh Dutta

Torrefied biomass is a green alternative to coal, and thus the interest in the torrefaction process is rising fast. Different manufacturers are offering different patented designs of torrefier with data on varying operating and process conditions each claiming their superiority over others. The choice of torrefaction technology has become exceptionally difficult because of a near absence of a comparative assessment of different types of reactors on a common base. This work attempts to fill this important knowledge gap in torrefaction technology by reviewing available types of reactors, and comparing their torrefaction performance common basis and examining the commercial implication of reactor choice. After reviewing available patent and technologies offered, torrefiers are classified broadly under two generic groups: indirectly heated and directly heated. Four generic types of reactors, convective heating, fluidized bed, rotating drum and microwave reactor were studied in this research. Convective and fluidized beds have direct heating, rotating reactors has indirect heating while microwave involves a volumetric heating (a subgroup of direct heating) mechanism. A standard sample of biomass (25 mm diameter × 64 mm long poplar wood) was torrefied in each of these types of reactors under identical conditions. The mass yield, energy density and energy yield of the wood after torrefaction were measured and compared. Rotating drum achieved lowest mass yield but highest energy density. The difference between two direct heating, convective heating and fluidized beds was small. Microwave provided only localized torrefaction in this series of tests. Indirectly heated reactors might be suitable for a plant near the biomass source while directly heated plant would give better value at the user end.


2000 ◽  
Vol 33 (7) ◽  
pp. 579-586 ◽  
Author(s):  
Stephan Jampen ◽  
Ian J Britt ◽  
Marvin A Tung

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