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03 / 2003
KF_14_03_e
The determination of water in polyamide
The amount of water in two different plastics was determined by using the Karl-FischerTitrator AQUA 40.00. The Head-Space-Module was used for complete heating of the
plastics. In addition, ethylene glycol was used as a reference substance and analyzed
directly in the measuring cell of the AQUA 40.00.
The following displays the obtained results.
The complete heating procedure of polyamide at a temperature range of
30° C – 280° C
By using the temperature programmed complete heating, one can differentiate among the
different bonding types of the water. In addition, the ideal complete drying temperature can
be determined. The following figure shows a typical temperature programmed complete
heating curve of polyamide.
Temperature programmed complete heating of polyamide granular material: 30-280° C increasing by 3° C/min
The right diagram shows that the release of water from the polyamide granular material takes
place within a wide-spread temperature range of 50–260° C. Below 50° C, only the
adsorptive bonded surface water is desorbed. The ideal complete heating temperature of
polyamide therefore lies at approx. 280° C.
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Developed by: ECH Elektrochemie Halle GmbH, Weinbergweg 23, D-06120 Halle/S.
Telefon: 0345/5583-711, Telefax: 0345/5583-710, internet: http://www.ech.de, e-mail: [email protected]
03 / 2003
KF_14_03_e
The isothermal complete heating of polyamide at 280° C
The polyamide samples were completely heated at 280° C.
The following figure shows a typical measurement curve for each product. The time of
measurement lies between 5 and 10 min, the ideal weighed portion is approx. 300-400 mg.
The sample’s typical titration curve: component part from PA 6.6
The sample’s typical titration curve: granular material from PA 6
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Developed by: ECH Elektrochemie Halle GmbH, Weinbergweg 23, D-06120 Halle/S.
Telefon: 0345/5583-711, Telefax: 0345/5583-710, internet: http://www.ech.de, e-mail: [email protected]
03 / 2003
KF_14_03_e
The bulk of water from both plastic samples is desorbed very quickly (within 5 min) at 280° C.
The determination of water in ethylene glycol
The determination of water in ethylene glycol should demonstrate the high velocity of
titrations using the AQUA 40.00. Very short measurement periods (approx. 1-2 min) are
achieved.
A typical titration curve of ethylene glycol
Due to the fact that titration is done very quickly, the total complete heating process as well
as the resulting release of water from the sample can be described by using the oven. Thus,
it is possible to derive kinetic and/or thermodynamic substance specific data from the results
of the Karl-Fischer-Titration.
Summary of results
The following is a summary of the results. Determination was performed three times for each
sample. The reproducibility achieved is very high in the polyamides as well as in ethylene
glycol. The water content of the PA component is higher than that of the granular material.
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Developed by: ECH Elektrochemie Halle GmbH, Weinbergweg 23, D-06120 Halle/S.
Telefon: 0345/5583-711, Telefax: 0345/5583-710, internet: http://www.ech.de, e-mail: [email protected]
03 / 2003
KF_14_03_e
List of results (each sample tested three times)
Conclusion
The water content of polyamides can be determined exactly and absolutely reliable using the
Head-Space-Module for complete heating. One advantage in using the temperature
programmed complete heating is the possibility to make further predictions about the origin
and bonding tightness of the water. It is also possible to determine the rate at which water is
released. This is an important criteria, i.e., for enabling the emulation and optimization of the
drying course of technical processes in a laboratory. The AQUA 40.00’s comfortable
computer controlled-software gives you various possibilities for comparing results and
furthermore, for their interpretation.
Measurement technology
•
Karl-Fischer-Titrator AQUA 40.00 equipped with a Head-Space-Module
Add-on options:
• Autosampler for head-space- module
• Reagent changing module
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Developed by: ECH Elektrochemie Halle GmbH, Weinbergweg 23, D-06120 Halle/S.
Telefon: 0345/5583-711, Telefax: 0345/5583-710, internet: http://www.ech.de, e-mail: [email protected]