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Kiya-Oglu, V. N.; Serkov, A. T.

doi:10.1023/a:1004103607687

Fibre Chemistry

2000

DOI: 10.1023/a:1004103607687

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V. N. Kiya-Oglu

A. T. Serkov

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“…According to Troutons law, η = 3μ for maximally low velocity gradients, which can probably be extended over a wider range in a first approximation, or obey the same exponential law of both longitudinal flow and shear flow for different exponents q = n = 0.7 for LC solutions of PPTA corresponding to practical observations on resonance in drawing of jets [3].…”

mentioning

confidence: 92%

“…We evaluated the applicability of the FisherDenn model to jet flow of LC sulfuric-acid solutions of PPTA and compared this model with the model of flow proposed previously in [2,3].…”

mentioning

confidence: 99%

“…Since the normal stress varies over the length of the jet in conditions of extension from the spinneret channel outlet to the takeup device, the velocity gradient of longitudinal flow dυ/dx also includes the change in elastic deformation according to the equation [2] dx dõ QG…”

mentioning

confidence: 99%

“…Let us define longitudinal purely viscous flow as obeying an exponential law with the expression for the viscosity coefficient [2] .…”

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confidence: 99%

“…The corresponding constant value of the longitudinal stress τ′ max = η′ min (dυ/dx) max in the physical sense is the stress for the viscous constituents of the medium, and their viscosity only changes under its effect when infinitely large longitudinal stress τ acts on them. (For a Maxwell liquid with a constant viscosity, this stress is τ′ = 0, and for the model of flow in [2,3], it does not differ from the longitudinal stress of the medium responding to tensile force.) The physical element of this model is difficult to represent.…”

mentioning

confidence: 99%

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Modeling of jet flow of poly-(p-phenylene terephthalamide) solution

Petrova

Kiya-Oglu

2007

Fibre Chem

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The limited applicability of the FisherDenn model of a viscoelastic liquid for describing jet flow of LC sulfuric acid solutions of poly-(p-phenylene terephthalamide) in dry-wet fibre spinning is demonstrated. Jet flow of polymers is an important stage in spinning fibres. Their physicomechanical properties are usually dependent on the conductions of conducting jet flow. High-strength fibres made of poly-(p-phenylene terephthalamide) (PPTA) and copolymers with a predominant content of PPTA units are made by dry-wet spinning through an air gap 5-15 mm in size with a fibre takeup speed of 70-400 m/min and higher. In conditions of flow in 5-8-fold drafting of the jet in the air gap, 19-20% liquid-crystalline (LC) sulfuric-acid solutions of PPTA (with a viscosity of 100-200 Pa⋅sec, temperature of 80°C) exhibit viscoelastic properties, since their residence time in the air gap is brief and does not exceed 0.01 sec, which is commensurate with the stress relaxation time in the solution. FisherDenn jet flow of viscoelastic was described with a generalized Maxwell model of a liquid with one relaxation time, an exponential law of viscous flow, and a constant modulus of hyperelasticity [1]. We evaluated the applicability of the FisherDenn model to jet flow of LC sulfuric-acid solutions of PPTA and compared this model with the model of flow proposed previously in [2, 3].The system of differential equations of the rheological state of a viscoelastic medium is significantly simplified in the FisherDenn model in the hypothesis of the absence of comprehensive compression of the medium in jet flow a steady-state process of isothermal spinning. This approximation is very widespread, since it only introduces a small error [4,5], but allows significantly simplifying the calculations and finding analytical solutions of the equations. As a result, one rheological state equation of the following form is obtained

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mentioning

confidence: 92%

“…We evaluated the applicability of the FisherDenn model to jet flow of LC sulfuric-acid solutions of PPTA and compared this model with the model of flow proposed previously in [2,3].…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…Let us define longitudinal purely viscous flow as obeying an exponential law with the expression for the viscosity coefficient [2] .…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Modeling of jet flow of poly-(p-phenylene terephthalamide) solution

Petrova

Kiya-Oglu

2007

Fibre Chem

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High-strength, high-modulus fibres based on linear polymers: principles of production, structure, properties, use

Perepelkin

2010

Fibre Chem

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The evolution of modern technology, transportation, sports, and tourism is greatly determined by the use of new materials, especially materials capable of withstanding limiting mechanical loads. Materials with high specifi c mechanical characteristics that allow creating highly reliable articles and structures of minimum weight are promising [1][2][3][4][5][6][7][8]. The highstrength and high-modulus fi bres used for this purpose belong to the low-and medium-tonnage group. They are manufactured from different kinds of aromatic and some aliphatic polymers. The highly oriented structure, which makes it possible to attain extremal mechanical properties in highly loaded textile items and high-strength composites, is a distinctive feature of these fi bres.The basic kinds of high-strength, high-modulus fi bres used on large scales are fi bres made from aromatic p-polyamides. They were created in the 1970s at almost the same time in the USA and Russia [3][4][5][6][7]. As a result of conducting extensive research on synthesis of new fi bre-forming polymers, creating the corresponding technologies, and investigating the structure and properties of these types of fi bres, development was basically of several kinds: -high-strength and high-modulus para-aramid fi bres based on poly-p-phenylene terephthalamide (PPTA -Twaron, Netherlands, and Kevlar, USA) with a dynamic deformation modulus of 90 to 160 GPa and a mechanical deformation modulus of 70 to 120 GPa; -high-modulus para-aramid fi bres made from heterocyclic p-polyamides and the close copolyamides (SVM, Rusar, and Armos, Russia) with a dynamic deformation modulus of 120 to 160 GPa and a mechanical deformation modulus of 95 to 120 GPa. SVM fi bres (historically, the fi rst kind of high-modulus heterocyclic aromatic fi bres) have been based on polyamidobenzimidazole synthesized from heterocyclic p-diamine and terephthalochloride. The copolymeric heterocyclic para-aromatic fi bres Armos and Rusar are based on the same components, with incorporation of p-phenylenediamine as the third comonomer.Other kinds of high-strength and high-modulus fi bres have also been created: -fi bres made from a copolymer close in composition to poly-p-phenylene terephthalamide with a 5-15% aromatic comonomer content (Terlon, Russia). These fi bres differ little in composition and properties from PPTA fi bres;-high-strength fi bres based on para/meta-polyaramid synthesized from p-phenylenediamine, para/metadiaminodiphenyl oxide, and terephthalic acid with a dynamic deformation modulus of 90 to 110 GPa, mechanical deformation modulus of 60 to 80 GPa for high-strength textile articles and reinforcement of elastomeric composites, primarily rubbertextile items (Technora, Japan). 2

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Cited by 2 publications

References 2 publications

Modeling of jet flow of poly-(p-phenylene terephthalamide) solution

Modeling of jet flow of poly-(p-phenylene terephthalamide) solution

High-strength, high-modulus fibres based on linear polymers: principles of production, structure, properties, use

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