Preparative TREF and Size Exclusion Characterization of Olefin Oligomers
Preparative TREF combined with high-temperature SEC isolates and quantifies migrating sub-1000 Da polyolefin oligomers to verify food contact safety compliance.
Universal Calibration
Meaning
Liquid chromatography calibration methods establish a relationship between retention volume and molecular size for polymers of varying chemical compositions. Gel permeation chromatography relies on universal calibration to determine the absolute molecular weight distribution of unknown resin batches. This approach eliminates the need for chemispecific polymer standards by using the hydrodynamic volume as the unifying parameter.
Viscosity and retention time measurements are combined to plot the calibration curve.
Chromatography Principle
Intrinsic viscosity multiplied by molecular weight yields the hydrodynamic volume, which is identical for all polymer chains at a given elution volume. Viscometric detectors connected in series with refractive index detectors measure these properties directly. Plotting this product against retention volume creates a single calibration curve.
Molecular Characterisation
Determining the true molecular weight distribution is necessary when evaluating recycled polymer blends. Impurities or blended fractions alter the molecular weight, affecting the melt flow index of the recycled plastic. Accurate distributions help molders predict how the material will behave during injection.
Moulding Application
Predicting polymer melt flow characteristics based on absolute molecular weight prevents unexpected viscosity changes in the injection mold. Lots with low molecular weight fractions may experience flash, whereas high molecular weights cause short shots. High repeatability during molding runs is achieved by screening incoming raw materials.