Meaning
Analytical procedure determines the water content in plastics using a relative humidity sensor. The protocol for astm d6980 provides a non-chemical alternative to traditional titration methods by heating the specimen in a sealed chamber. Moisture evaporates from the resin and flows across a sensor that measures the change in air moisture.
Measurement Mechanism
Calculation of the final moisture percentage relies on the equilibrium reached between the sample and the carrier gas. A machine following astm d6980 heats the pellets to a temperature just below their melting point to release trapped water without degrading the polymer chains. Dry air or nitrogen transports the vapor to the detector where the relative humidity is converted into a mass-based water content reading.
Total test time usually spans ten to fifteen minutes depending on the sample size and initial moisture load.
Instrument Sensitivity
Detection limits for this method sit well within the requirements for processing engineering grade resins. Most equipment using astm d6980 can resolve moisture levels as low as 0.005 percent. This precision is necessary for materials like polyethylene terephthalate where slight variations in water content cause massive drops in intrinsic viscosity.
Field Comparison
Accuracy matches that of more complex laboratory tests while offering faster results on the production floor. Because astm d6980 avoids the use of hazardous reagents, the procedure is inherently safer than chemical titration methods.
