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.
Bunsen Reaction
Meaning
Chemical oxidation of sulfur dioxide by iodine in the presence of water and a buffering base. Analytical testing of resin moisture content relies on the bunsen reaction to quantify trace water before melt processing. This reaction proceeds stoichiometrically, meaning that one mole of iodine is consumed for each mole of water present in the polymer sample.
Reagent Chemistry
Coulometric titration generates the iodine needed for the reaction directly in the test cell. An automated system measures the electric current required to produce this iodine, providing an exact measure of moisture in resin pellets. The bunsen reaction occurs rapidly when the pH of the solution remains within the ideal range.
This reaction must be fully completed to prevent inaccurate moisture calculations that could lead to processing wet nylon or polyester.
Analytical Calibration
Standard calibration runs verify the efficiency of the reaction using known water standards. This step ensures that the instrument reports correct moisture levels for difficult-to-dry engineering resins. Moulders run these tests to establish the baseline performance of their analytical equipment.
Consistent reaction performance prevents the introduction of uncalibrated errors into the daily production cycle.
Moulding Protection
Accurate reaction tracking prevents the hydrolysis of polymer chains during high-temperature injection moulding. This chemistry safeguards mechanical properties in the final product.