Meaning
Electrolytic measurement of electrical charge provides the basis for determining low-level water concentration in hygroscopic polymers. A microampere coulometer uses the Karl Fischer reaction to quantify moisture content in resins like nylon or polycarbonate. Testing with this equipment ensures that material has been dried sufficiently to prevent hydrolytic degradation during processing.
The device operates by measuring the total current required to reach an electrochemical endpoint.
Titration Chemistry
Reagents inside the glass cell react with the water extracted from a heated resin sample. Iodine is generated at the anode in proportion to the electric current passed through the solution. This process continues until all available water is consumed.
Moisture Sensitivity
Processing resins with excess moisture leads to permanent loss of molecular weight and mechanical strength. Water acts as a catalyst for chain scission at high temperatures, which turns a tough engineering plastic into a brittle component. Even small amounts of water, measured in parts per million, can cause visible surface defects like splay or internal bubbling.
A coulometric test provides much higher resolution than loss-on-drying scales. This precision is necessary for polymers that have a very narrow window for processing.
Drying Verification
Laboratory technicians use the instrument to audit the efficiency of desiccant dryers on the production floor. Regular testing prevents the use of under-dried material that would result in part failure. Successful results confirm that the drying time and temperature were sufficient for the specific resin batch.
