Meaning
Analytical test method used to measure the moisture content of polymer materials by water evaporation and titration. Processing engineering relies on ISO 15512 Method C to verify that hygroscopic resins have been dried to the low levels required for high quality injection moulding.
Evaporation Mechanism
A solid polymer sample is heated in an oven to drive off any trapped water without melting or decomposing the plastic itself. Dry carrier gas flows through the oven to transport the released water vapour into the detection cell. This method separates the moisture from the polymer matrix to prevent chemical interferences during the test.
Coulometric Measurement
The water vapour enters a Karl Fischer titration cell where it reacts with iodine in the presence of an anode. An electric current is used to generate the iodine required for the reaction, and the total charge consumed is measured to calculate the water mass. This coulometric technique provides high accuracy even for minute water amounts down to a few parts per million.
Industrial Application
Moulding shops use this method to audit the performance of their resin dryers before starting a production run. While loss on drying methods can mistake volatile additives for moisture, the selectivity of ISO 15512 Method C provides a true water value. Using this standard prevents cosmetic surface defects and mechanical failures in high-performance polycarbonate and polyamide components.
