Recycled Polyolefin Oligomer Identification for Food Contact Clearance
Clearing recycled polyolefins for food contact demands HPLC-GC-FID and GCxGC-MS identification of oligomeric fractions evaluated against TTC thresholds.
POSH Identification
Meaning
Chemical profiling detects the saturated hydrocarbon oligomers that migrate from polyethylene and polypropylene packaging into food simulants. Running POSH identification separates these polymer-derived compounds from external mineral oil contaminants during regulatory compliance testing. This distinction ensures that packaging materials are not falsely rejected due to non-harmful hydrocarbons that originate from the plastic matrix itself.
Oligomer Origin
Low molecular weight saturated hydrocarbons are inherent to the structure of manufactured polyolefins. During POSH identification, the analysis focuses on linear and branched alkanes with fewer than forty carbon atoms. These molecules migrate easily because their small size allows them to diffuse through the polymer network.
Measuring these compounds is essential for verifying the purity of virgin resins intended for sensitive packaging.
Analytical Separation
Advanced chromatographic methods are utilized to resolve these oligomers from other packaging components. Analysts employ techniques that separate the saturated hydrocarbons from aromatic and mono-unsaturated fractions. The resulting chromatogram displays a series of regularly spaced peaks that are characteristic of the polyolefin repeating units.
In contrast, mineral oils present a broad, unresolved peak shape that is easily distinguished from the polymer oligomer pattern. This analytical clarity prevents false positive results and confirms the safety of the plastic packaging.
Moulding Influence
High processing temperatures can increase the concentration of these mobile oligomers by promoting chain degradation. By optimizing injection velocity and cooling rates, moulders can minimize the formation of these low-weight molecules. This manufacturing control is vital for maintaining low migration values over long production runs.