Coulometric Titration Baseline Drift Calibration Methods
Drift calibration isolates cell background current from true sample moisture, preventing hydrolytic degradation and avoiding false incoming resin lot rejections.
Moisture Extraction
Meaning
Vapour phase separation removes water molecules from a polymer matrix before melt processing or laboratory analysis. This moisture extraction process is essential for resins that suffer from hydrolytic degradation when heated in the injection cylinder. For materials like nylon or polycarbonate, the rate of water removal determines the total drying cycle time.
Effective extraction ensures that the polymer melt remains stable and retains its molecular weight.
Thermal Desorption
Heating polymer pellets below their softening point increases the diffusion of water through the resin. This moisture extraction step occurs in a desiccant hopper or a laboratory oven connected to a titration cell. If the temperature is too low, the water remains trapped inside the pellet cores.
This incomplete release leads to faulty moisture measurements or brittle moulded parts.
Carrier Transport
Dry nitrogen gas sweeps the released vapour from the sample vial into the titration vessel. Efficient moisture extraction relies on a constant flow rate of this carrier gas to prevent condensation in the transfer lines. Cold spots in the flow path cause the water to recondense before it can be measured.
This transport failure leads to false low moisture readings.
Defect Prevention
Correct extraction prevents cosmetic splay and structural weakness in high-precision parts.