Karl Fischer Titration Interference Mechanisms in Recycled Polyester Flake Qualification
Karl Fischer moisture testing of recycled PET flake requires thermal desorption at 170 C with methanol-free reagents to eliminate volatile interference.
Dry Nitrogen
Meaning
Gaseous medium processed to remove virtually all moisture content for use in sensitive material drying and analytical testing. Moisture determination of engineering plastics uses dry nitrogen to sweep released moisture from heated resin samples into the detection chamber without adding ambient humidity. This inert gas provides a moisture-free atmosphere that prevents atmospheric water from skewing the titration results.
Moisture Extraction
Karl Fischer oven systems depend on a steady supply of this gas to carry water vapour from the sample vial. Using dry nitrogen avoids the introduction of outside moisture during high-temperature testing. The gas must have a dew point below minus forty degrees Celsius to ensure that no moisture is added to the measurement stream.
This high level of dryness is necessary for verifying the moisture levels of resins like PET or polycarbonate before moulding.
Thermal Preservation
Standard air can cause oxidation when heated to the high temperatures needed for polymer moisture extraction. These high temperatures can trigger oxidation when standard air is present. The inert properties of the gas prevent these oxidative side reactions during the heating cycle.
This protection ensures that the instrument measures only the actual water content of the plastic.
Material Protection
Purging hopper driers with this dry gas prevents oxidation and premature polymer degradation during the heating cycle. This inert atmosphere maintains the resin’s molecular weight during long holding times.