Meaning
Signal processing techniques employed in automated titration calculate and remove the continuous background current generated by ambient moisture leaks in the reaction vessel. By utilizing coulometric baseline correction, moisture analyzers adjust the endpoint detection threshold based on the real-time drift of the titration cell. This method is restricted to closed reaction cells where the background drift remains relatively stable during the analysis period.
Measurement Integrity
The titration system measures the electrical current required to generate iodine, which reacts with water in the titration cell. Ambient moisture slowly leaking into the vessel creates a continuous background current that would falsely increase the apparent moisture of the resin. This baseline correction measures this background current just before sample introduction and subtracts it dynamically from the total current measured during the analysis.
This ensure that only the water released from the polymer sample is counted, yielding highly accurate moisture measurements.
Processing Impact
For high-performance polymers like polybutylene terephthalate, moisture levels must be held below a tight threshold to prevent degradation during molding. Using uncorrected titration data might lead a moulder to believe the resin is drier than it is, leading to processing failures. Accurate baseline corrections ensure that the measured moisture values are reliable, allowing for proper process control.
Drift Mitigation
Excessive background drift, often caused by degraded reagents or compromised seals, can overwhelm the correction capability of the instrument. Maintaining the titration cell by replacing the seals and reagent when the baseline drift exceeds a specified threshold ensures the correction remains accurate. This practice minimizes the risk of false positives and ensures the highest precision in resin moisture testing.
