Meaning
Analytical chemistry methods determining trace moisture content in solid or liquid samples by quantitatively reacting water with an iodine-based reagent solution. Performing Karl Fischer titration governs moisture testing for hygroscopic engineering polymers prior to melt processing. It does not apply to surface moisture measurement on non-porous metal or glass surfaces.
Chemical Reaction
Sample ovens vaporize internal water from resin pellets, sweeping moisture vapor into a sealed titration cell via dry nitrogen carrier gas. Conducting Karl Fischer titration uses an electrochemical cell to generate iodine that neutralizes water until an endpoint sensor detects zero remaining moisture. Precise titration prevents processing defects like hydrolytic degradation.
Measurement Audit
Quality control protocols validate laboratory testing equipment using certified water standards before analyzing production polymer lots. Running Karl Fischer titration to confirm moisture readings below two hundred parts per million ensures proper resin drying prior to molding. Waiving moisture testing on engineering plastics to speed up production release leads to structural embrittlement and splay defects in finished parts.
Operational Boundary
Volatile additives in specialized polymer formulations interfere with iodine reactions inside the titration cell. Matrix interference in Karl Fischer titration requires carrier gas temperature settings to remain below resin melting points to avoid releasing non-water decomposition products. Evaporation profiles optimize moisture extraction.
