Meaning
Nonvolatile residues represent the mass of material extracted from a polymer substrate using hexane under specific temperature conditions. These hexane extractables define the quantity of low molecular weight components, such as oligomers, waxes, and processing aids, that leach from a material when in contact with solvents. The quantification process determines the compliance of plastic packaging with food contact regulations by ensuring that migration levels remain below established health safety limits.
Migration Risk
Excessive levels of these substances suggest a high potential for additive transfer into food products during thermal processing or long term storage. Polyolefin resins frequently exhibit these characteristics because their production involves catalysts that leave residual hydrocarbons within the polymer matrix. High concentrations cause surface tackiness on finished films and interfere with the adhesion of printing inks or laminate layers.
Regrind inclusion further complicates this profile by accumulating mobile species over multiple heating cycles. Moulders monitor these levels to prevent odour transfer and migration of restricted monomers into consumer goods.
Solvent Interaction
Hexane functions as a model solvent for nonpolar fatty foods during laboratory verification of polymer chemistry. The test procedure involves refluxing the sample in the solvent for a defined duration and subsequently evaporating the liquid to measure the remaining solid mass. Equilibrium between the polymer and the solvent determines the total mass transfer, which depends on the crystallinity and density of the resin grade.
Lower density materials typically yield higher extractable values due to the increased free volume between polymer chains.
Analytical Variance
Datasheet values provide a baseline for virgin material performance rather than the absolute performance of a moulded part. Part geometry and cooling rates during injection moulding alter the internal structure of the plastic, which dictates the amount of species available for extraction. Deviations from the baseline occur when the conversion process introduces thermal degradation or oxidation products that increase solubility.
Validation of the final component requires testing the exact material and geometry used in production to ensure the specific extractable profile meets safety criteria.
