Polyolefin Low Molecular Weight Extraction and Migration Testing
Polyolefin migration compliance requires batch-specific testing for low molecular weight hydrocarbons using accredited simulants, exact temperatures, and GC-MS.
N-Hexane Extractables
Meaning
Non-polar solvent-soluble components represent the portion of a polymer that migrates into a specific liquid medium under defined temperature and time conditions. Measuring n-hexane extractables identifies the presence of low molecular weight species or additives that could leach from a finished part. This measurement is standard in the evaluation of polyolefins intended for contact with food or medical fluids.
Regulatory Compliance
Food safety authorities set strict limits on the mass percentage of material that can be removed by the solvent. If a resin exceeds the allowed level of n-hexane extractables, it cannot be used for thin film or container applications. This value acts as a gateway for material acceptance in high regulated markets.
Migration Profile
High levels of extractable content often indicate a broad molecular weight distribution or excessive lubricant use. These components can migrate to the surface of a part to cause tackiness or visual blooming. Monitoring this property helps maintain the aesthetic and functional quality of moulded products.
Material Assessment
Pellets or film samples are weighed before and after immersion in boiling n-hexane for a fixed duration. The difference in mass reveals the total extractable content as a weight percentage. Drying the sample to a constant weight is necessary to ensure all residual solvent has evaporated before the final measurement.
This step prevents errors where trapped solvent inflates the final mass and masks the true extent of material loss. Total extraction time typically ranges from two to several hours depending on the specific material thickness.