Meaning
Low molecular weight saturated hydrocarbons derived from the polymer backbone itself constitute a distinct fraction of potential migrants in plastic packaging. These polyolefin oligomeric hydrocarbons or pooh are created during the polymerization process or through thermal degradation. They are chemically similar to the mineral oil saturated hydrocarbons found in external contaminants.
Distinguishing these internal migrants from external oils is necessary for accurate source tracking.
Molecular Origin
Side reactions during the manufacture of polyethylene or polypropylene produce short-chain molecules. Because pooh are formed from the same monomers as the bulk plastic, they are integrated into the resin.
Extraction Method
Strong solvents are used to dissolve the polymer and release the oligomeric fraction. During the analysis of pooh, liquid chromatography separates these saturated molecules from any aromatic additives. The resulting extract is then analyzed using gas chromatography to determine the molecular weight distribution.
This profile helps identify whether the hydrocarbons come from the resin itself or from processing lubricants. Labs use this data to confirm the quality of virgin materials.
Safety Profile
Small molecules move through the plastic matrix and can reach the surface of a moulded part. While pooh are generally considered to have low toxicity, their total concentration is often regulated in food contact applications. Reducing the formation of these oligomers during resin production improves the purity of the final product.
