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Angaben zur Quelle [Bearbeiten]

Autor     A. K. Gupta
Titel    Characterization of polymers and fibres
Sammlung    Manufactured Fibre Technology
Herausgeber    V. B. Gupta, V. K. Kothari
Verlag    Springer
Jahr    1997
Seiten    203-247
ISBN    978-94-010-6473-6
DOI    10.1007/978-94-011-5854-1
URL    http://link.springer.com/book/10.1007%2F978-94-011-5854-1

Literaturverz.   

yes
Fußnoten    yes
Fragmente    3


Fragmente der Quelle:
[1.] Mrs/Fragment 064 03 - Diskussion
Zuletzt bearbeitet: 2015-05-16 19:17:23 WiseWoman
Fragment, Gesichtet, Gupta 1997, Mrs, SMWFragment, Schutzlevel sysop, Verschleierung

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Quelle: Gupta 1997
Seite(n): 238, Zeilen: 15-17
5.5. Thermal characterization [242-244]

Thermoanalytical techniques are used for characterization of glass transition and melting temperature, thermal stability and other properties as a function of temperature of polymers and fibers.


[242] A. Turi, Thermal characterization of polymeric materials / ed. by Edith 2 London : Academic Press, 1997

[243] Höhne, Günther, Differential scanning calorimetry : with 19 tables., Berlin : Springer, 2003

[244] E. A. Turi, thermal analysis of polymers, Academic press, New York1982 [sic]

10.4 THERMAL CHARACTERIZATION

Thermoanalytical techniques are used for characterization of glass transition and melting temperatures, thermal stability and other properties as a function of temperature of polymers and fibres [22].


22. Turi, E.A. (1982) Thermal Analysis of Polymers, Academic Press, New York

Anmerkungen

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Sichter
(Klgn), (Hindemith), WiseWoman

[2.] Mrs/Fragment 070 04 - Diskussion
Zuletzt bearbeitet: 2015-04-19 19:11:19 WiseWoman
Fragment, Gesichtet, Gupta 1997, Mrs, SMWFragment, Schutzlevel sysop, Verschleierung

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Polymer solutions show very high viscosity which varies not only with concentration but also with molecular weight. This property of polymers has been used as a method of determining the molecular weight of polymers. A parameter called intrinsic viscosity [η] is strongly dependent on the molecular dimensions of the solute particles. Since molecular dimensions depend on molecular weight, suitable calibration curves have been developed which led to well-known relation called the Mark-Houwink equation:

Mrs 070a diss.png

Where k and a are constants and M is the molecular weight of the polymer. M may represent Mn or Mw, depending on the molecular weight average used in the calibration curve. The intrinsic viscosity [η] is defined as follow:

Mrs 070b diss.png

Where η and η0 are the viscosities of the solution and the solvent, respectively, and c is the concentration. The last expression on the right-hand side is simply to define the symbol ηsp (specific viscosity) in subsequent discussion. The intrinsic viscosity is therefore determined by plotting ηsp/c against c and extrapolating the plot to zero concentration, as shown in Figure 5.5

Polymer solutions show very high viscosity which varies not only with concentration but also with molecular weight. This property of polymers has been used as a method of determining the molecular weight of polymers.

A parameter called 'intrinsic viscosity' (also called 'limiting viscosity number' in modern nomenclature), denoted with brackets as [η], is strongly dependent on the molecular dimensions of the solute particles. Since molecular dimensions depend on molecular weight, suitable calibration curves have been developed which lead to a well-known relation called the Mark-Houwink equation:

Mrs 070a source.png

where K and a are constants and M is the molecular weight of the polymer. M may represent Mn or Mw, depending on the molecular weight average used in the calibration curve.

The intrinsic viscosity [η] is defined as follows:

Mrs 070b source.png

where η and η0 are the viscosities of the solution and the solvent, respectively, and c is the concentration. The last expression on the right-hand side is simply to define the symbol ηsp (specific viscosity) in subsequent discussion. The intrinsic viscosity is therefore determined by plotting ηsp/c against c and extrapolating the plot to zero concentration, as shown in Fig. 10.8.

Anmerkungen

The source is not mentioned.

Sichter
(Hindemith), SleepyHollow02

[3.] Mrs/Fragment 074 01 - Diskussion
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Fragment, Gesichtet, Gupta 1997, Mrs, SMWFragment, Schutzlevel sysop, Verschleierung

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Quelle: Gupta 1997
Seite(n): 215, 216, Zeilen: 215: last paragraph; 216: 1 ff.
5.6.3. Gel permeation chromatography (GPC)

Gel permeation chromatography (GPC) is quite useful for routine estimate of molecular weight, owing to its convenience and the possibility of simultaneous evaluation of various averages of molecular weight, thus providing information about the molecular weight distribution. The GPC technique is based on the separation of solute molecules according to their size by passing the polymer solution through a column packed with microporous gel particles. A known small volume of polymer solution is injected into an already stabilized current of the solvent through the column, and then the out flowing liquid from the column is analyzed for the concentration of the solute as a function of time. Separations of molecules occur by their preferential penetration into the pores of the gel filled in the column, depending on their sizes. Small molecules penetrate more easily than the larger one, while the very large ones may either partially penetrate or not penetrate at all. Thus, during the passage of the solution through the column the largest molecules will take the shortest time while the smallest one will take the longest time to elute from the column. The eluting liquid passing through the detector is measured for its solute concentration through its refractive index or optical density. The detector signal, which is proportional to the solute concentration, thus gives a trace as a function of time or elution volume, as shown in Figure 5.6 for a polydisperse polymer sample.

Mrs 074a diss.png

Figure 5.6 Typical GPC curve for a polydisperse polymer sample.

(e) Gel permeation chromatography

Gel permeation chromatography (GPC) is quite useful for routine estimate of molecular weight, owing to its convenience and the possibility of simultaneous evaluation of various averages of molecular weight, thus providing information about the molecular weight distribution.

[page 216]

Mrs 074a source.png

Fig. 10.9 Typical GPC curve for a polydisperse polymer sample.

The GPC technique is based on the separation of solute molecules according to their sizes by passing the polymer solution through a column packed with microporous gel particles. A known small volume of polymer solution is injected into an already stabilized current of the solvent through the column, and then the out-flowing liquid from the column is analysed for the concentration of the solute as a function of time. Separation of molecules occurs by their preferential penetration into the pores of the gel filled in the column, depending on their sizes. Small molecules penetrate more easily than the larger ones, while the very large ones may either partially penetrate or not penetrate at all. Thus, during the passage of the solution through the column the largest molecules will take the shortest time while the smallest ones will take the longest time to elute from the column. The eluting liquid passing through a detector is measured for its solute concentration through its refractive index or optical density. The detector signal, which is proportional to the solute concentration, thus gives a trace as a function of time or elution volume, as shown in Fig. 10.9 for a polydisperse polymer sample.

Anmerkungen

The source is not mentioned. The two figures are similar, but not identical.

Sichter
(Hindemith), SleepyHollow02

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