Excluded volume theory of rigid plates in solution using continuous orientation distributions

Guenthner, A. J.; Kyu, Thein

doi:10.1002/1099-0488(20000915)38:18<2366::aid-polb40>3.0.co;2-q

Cited by 2 publications

(2 citation statements)

References 23 publications

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“…The development of skins on polymer fibers spun from polymer solutions is a well‐known phenomenon that has been observed in the manufacture of textile fibers from viscose and other polymers 20, 21. Mathematical models of the formation of skins were reviewed and extended by Guenthner and Kyu 22…”

Section: Resultsmentioning

confidence: 99%

Flat polymer ribbons and other shapes by electrospinning

Koombhongse¹,

Liu²,

Reneker³

2001

J Polym Sci B Polym Phys

755

507

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In addition to round nanofibers, electrospinning a polymer solution can produce thin fibers with a variety of cross-sectional shapes. Branched fibers, flat ribbons, ribbons with other shapes, and fibers that were split longitudinally from larger fibers were observed. The transverse dimensions of these asymmetric fibers were typically 1 or 2 m, measured in the widest direction. A correlation of the branches and bends, observed in high-frame-rate videography of the electrified jets of polymer solutions from which the ribbons and branched fibers were produced, suggest that these phenomena occur at scales ranging from around 1 mm to 1 m. The observation of fibers with these cross-sectional shapes from a number of different kinds of polymers and solvents indicates that fluid mechanical effects, electrical charge carried with the jet, and evaporation of the solvent all contributed to the formation of the fibers. The influence of a skin on the jets of polymer solutions accounts for a number of the observations. The observed shapes can be used as guides for the extension of mathematical or computer-generated models for the electrospinning process.

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Section: Resultsmentioning

confidence: 99%

Flat polymer ribbons and other shapes by electrospinning

Koombhongse¹,

Liu²,

Reneker³

2001

J Polym Sci B Polym Phys

755

507

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“…Both theoretically and experimentally, hard disc dispersions show a transition from an isotropic to nematic liquid crystalline phase at a volume fraction f I-N E 3(h/d). [77][78][79][80][81][82][83][84][85][86][87][88][89] Wu et al 88 have shown that addition of a spherical attractive square well potential at the centre of mass of the discs facilitates the formation of orientationally ordered phases.…”

Section: How Is /* Related To the Properties Of The Precipitated Wax ...mentioning

confidence: 99%

How polymer additives reduce the pour point of hydrocarbon solvents containing wax crystals

Binks

Fletcher

Roberts

et al. 2015

Phys. Chem. Chem. Phys.

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We have investigated how four different pour point depressant (PPD) polymers affect the pour point transition in mixtures of a single pure wax in a solvent. We used either n-eicosane (C20), CH3(CH2)18CH3, n-tetracosane (C24), CH3(CH2)22CH3 or n-hexatriacontane (C36), CH3(CH2)34CH3 as the wax component with either n-heptane or toluene as the solvent component. For all wax-solvent combinations, the measured variation of wax solubility with temperature is well predicted by ideal solution theory. The variation of pour point temperature as a function of the overall wax concentration is quantitatively modelled using the idea that, for each overall wax concentration, the pour point occurs at a temperature at which a critical volume fraction ϕ* of wax crystals has precipitated. Close to the pour point temperature, extraction and examination of the wax crystals show they consist of polydisperse, irregularly-shaped platelets with axial ratios (h/d, where h is the plate thickness and d is the plate long dimension) in the range 0.005-0.05. It is found that the measured ϕ* values corresponding to the pour point transitions are weakly correlated with the wax crystal axial ratios (h/d) for all wax-solvent-PPD polymer combinations. These results indicate that the pour point transition occurs at a volume fraction larger than the value at which the volumes of rotation of the platelet crystals overlap, i.e., 2.5(h/d) < ϕ* < 11(h/d). PPD polymers work, in part, by increasing the wax crystal axial ratio (h/d), thereby increasing ϕ* and reducing the pour point temperature. Since the PPD's ability to modify the wax crystal shape relies on its adsorption to the crystal-solution surface, it is anticipated and observed experimentally that optimum PPD efficacy is correlated with the difference between the wax and the polymer solubility boundary temperatures. This finding and the mechanistic insight gained here provide the basis for a simple and rapid screening test to identify candidate species likely to be effective PPDs for particular wax systems.

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Excluded volume theory of rigid plates in solution using continuous orientation distributions

Cited by 2 publications

References 23 publications

Flat polymer ribbons and other shapes by electrospinning

Flat polymer ribbons and other shapes by electrospinning

How polymer additives reduce the pour point of hydrocarbon solvents containing wax crystals

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