Desiccant Dryer Operation and Basic Moisture Management in Hygroscopic Polymers
Maintaining desiccant dryers at -40°C dew point prevents hydrolytic degradation, preserving melt viscosity and mechanical performance in hygroscopic polymers.
Karl Fischer Titration ISO 15512 Method B
Meaning
Measuring the moisture content of engineering plastics by heating the sample and carrying the vapor to a reaction cell is a standardized test. This specific procedure, described in Karl Fischer titration ISO 15512 Method B, utilizes an oven to extract water from the polymer matrix without dissolving the sample. It is the primary method used to verify that nylon or polycarbonate resin is dry enough for injection molding.
Oven Extraction
The sample is placed in a sealed vial and heated in a specialized oven. This releases the moisture.
Chemical Reaction
A stream of dry carrier gas sweeps the released water vapor into the titration cell, where it reacts with iodine. The quantity of electric current needed to generate the iodine required to react with the water is measured. This coulometric measurement allows for the detection of water levels as low as a few micrograms.
Molding Quality
Knowing the precise water content before processing prevents hydrolytic degradation, which would otherwise reduce the molecular weight of the polymer. When moisture levels are held below the manufacturer’s specification, molded parts retain their full mechanical strength and do not exhibit splay or surface blemishes. This test is therefore critical for high-performance automotive and medical parts.