The water content in plastics, also known as moisture content, is a crucial quality parameter that significantly influences both the properties and processability of certain plastics. Elevated water content can result in degradation through hydrolysis or lead to surface imperfections. Furthermore, it can adversely impact the physical properties of some plastics.
Image Credit: Metrohm Middle East FZC
For the study presented in this article, the water content determination of polycarbonate pellets was determined using the 885 Compact Oven Sample Changer and 899 Coulometer.
The oven technique was employed as volatile compounds within the plastic interfered with the direct determination of water content via coulometric Karl Fischer titration.
Sample
- Plastic pellets (polycarbonate)
Sample Preparation
Approximately 3 g of sample was weighed into a sample vial, tightly closed with a cap, and placed on the rack of the 885 Compact Oven Sample Changer.
Configuration
Source: Metrohm Middle East FZC
| . |
. |
| 885 Compact Oven Sample Changer |
2.885.0010 |
| 899 Coulometer |
2.899.0010 |
| Remote cable |
6.2141.390 |
| Double Pt-wire electrode |
6.0341.100 |
| Generator electrode without diaphragm |
6.0345.100 |
Analysis
All measurements reported in this study were carried out at the same temperature with the same parameters.
After starting the sample series, the Sample Changer was moved to the conditioning vial. The needle then pierced the septum, the gas flow was initiated, and the titration vessel was conditioned.
A determination using an empty sample vial was then carried out to prepare the system and rinse all tubing.
Following system preparation, three blank values (empty sample vials) were determined, and the mean value of the blank was saved as a common variable. This value was then subtracted from the EP of the sample determination.
Subsequently, the water content of the samples was determined, and the titration vessel was reconditioned between each sample measurement.
Parameters 899 Coulometer
Source: Metrohm Middle East FZC
| . |
. |
| Conditioning |
on |
| Start drift |
10 μg/min |
| Drift correction |
auto |
| Automatic start |
off |
| Stabilizing time |
10 s |
| Cond. stop time |
off |
| Pause |
0 s |
| Endpoint at |
50 mV |
| Titration rate |
optimal |
| Stop criterion |
rel. drift |
| Relative stop drift |
10 μg/min |
| Extraction time |
120 s |
| Generator electrod |
without diaphragm |
| Generator current |
400 mA |
| Stirring rate |
15 |
| I(pol) |
10 μA |
| Temperature |
25 °C |
| Stop time |
off |
Parameters 885 Compact Oven Sample Changer
Source: Metrohm Middle East FZC
| . |
. |
| Temperature |
250 °C |
| Flow rate |
50 mL/min |
| Gas supply |
valve |
| Gas type |
nitrogen |
| End of series |
conditioning |
Results
Source: Metrohm Middle East FZC
| . |
. |
| Mean (n = 10) [μg/g] |
RSD [%] |
| 766.7 |
0.55 |
This information has been sourced, reviewed and adapted from materials provided by Metrohm Middle East FZC.
For more information on this source, please visit Metrohm Middle East FZC.