Determining Intrinsic Viscosity Loss in Polyethylene Terephthalate Processing
Intrinsic viscosity loss in PET processing is determined by measuring dilute solution flow time or capillary melt viscosity to quantify polymer chain cleavage.
Moisture Analysis
Meaning
Analytical procedure known as moisture analysis determines the amount of water present in a polymer resin before it is processed. This measurement is critical for materials that are sensitive to water-induced degradation during the melt phase. The process involves heating a sample and measuring either the weight loss or the specific chemical presence of water molecules.
Reliable results are necessary to verify that the drying equipment is functioning correctly and that the resin is in a state suitable for moulding or extrusion.
Thermogravimetric Method
Measuring the weight loss of a sample as it is heated is the most common way to perform moisture analysis in a production environment. A specialized balance, often called a moisture analyzer, heats the resin and tracks the decreasing weight until it stabilizes. This total weight loss is assumed to be water, although it can include other volatile substances like residual solvents or monomers.
This method is fast and easy to use on the factory floor for routine checks of drying bins.
Chemical Specificity
Distinguishing between water and other volatiles requires the use of the Karl Fischer titration. This method of moisture analysis uses a chemical reagent that only reacts with water, providing a much more accurate result for engineering resins. It is particularly important for polymers where even a few parts per million of water can cause significant hydrolysis.
High-precision labs use this technique to calibrate their less specific instruments and to troubleshoot quality issues.
Production Control
Consistent data from these tests allow the operator to adjust the drying time and temperature to match the incoming resin condition. If the moisture analysis shows that the resin is too wet, the moulding cycle should not be started, as it would lead to brittle parts and surface defects. These records provide a traceability trail that proves the material was processed according to the manufacturer’s recommendations.
Effective control of water content is the foundation of a stable and repeatable moulding process.
Coulometric Baseline Deconvolution for Recycled Polyethylene Terephthalate Sourcing Quality Control
Coulometric baseline deconvolution separates true matrix moisture from organic volatile interference in rPET, preventing false lot rejections and IV degradation.