Karl Fischer Titration Interference Mechanisms in Recycled Polyester Flake Qualification
Karl Fischer moisture testing of recycled PET flake requires thermal desorption at 170 C with methanol-free reagents to eliminate volatile interference.
Carrier Gas
Meaning
Purging medium used in headspace moisture analysis to sweep volatilized water from heated polymer resins into a titration vessel. Accurate trace moisture measurement depends on a carrier gas that is completely free of external humidity. This gas carries the released water vapour from the oven to the analytical cell without allowing any ambient moisture to contaminate the sample.
Moisture Transport
Dry nitrogen is the most common gas chosen for this analytical process. The carrier gas must flow at a steady rate to ensure complete moisture extraction from the polymer matrix. Any fluctuation in gas purity introduces external moisture, which inflates the measured water content of the resin.
This inflation leads to unnecessary drying cycles and higher energy costs for the processing plant.
Flow Control
Precise regulation of the gas stream prevents temperature drops in the sample vial. Handlers adjust the flow rate to match the heating cycle of the specific resin grade being tested. A slow stream fails to carry all the released water, while an excessive rate cools the sample too quickly.
Automated flow controllers maintain the optimum balance to achieve repeatable testing runs.
Quality Assurance
Consistent gas delivery prevents false dry readings that cause cosmetic surface defects like silver streaks on moulded parts. This clean transport system guarantees reliable material moisture data.