Desiccant Dryer Dew Point Calibration and Karl Fischer Titration Verification
Dew point monitoring alone fails to guarantee dry resin; coulometric Karl Fischer titration per ISO 15512 Method B is mandatory to prevent hydrolytic scission.
Reagent Titer Calibration
Meaning
Analytical chemistry routines establish the strength and reactivity of the titrant used to measure moisture content in polymer samples. In Karl Fischer titration of plastic pellets, reagent titer calibration determines the exact amount of water that corresponds to a given volume of reagent. This calibration accounts for the slow degradation of the reagent over time due to exposure to air and temperature changes.
It must be performed regularly to ensure the accuracy of trace moisture measurements.
Measurement Calibration
Standard water samples with a known moisture content are injected into the titration cell to perform the test. Measuring the reaction of the reagent against these standards allows the software to calculate the correction factor, which is the reagent titer calibration value. If this value is incorrect, all subsequent moisture readings for the dried resin will be offset.
High Precision
Accurate titer values are necessary when measuring trace moisture in engineering plastics like polyamide or polyester. These materials must be dried to very low limits, so even a small error in the calibration can lead to a false pass. Molders rely on this step to verify that their drying processes are meeting the required specifications.
Technical Schedule
Titrant strength decreases over time as it absorbs moisture from the surroundings. Most laboratories run this calibration at the start of each shift or after changing the reagent bottle.