Meaning
Federal regulatory standard specifies chemical composition, extractable limits, melting point ranges, and density criteria for polyolefin polymers intended for food contact applications in the United States. Compliance under us fda 21 cfr 177 1520 requires polyethylene and polypropylene resins to pass specific hexane and xylene solubility limits based on end-use temperature conditions. Standard requirements stop at virgin olefin polymers and do not cover secondary additives or non-olefin structural layers.
Hexane Extractable Testing
Dissolving olefin samples in n-hexane at specified temperatures measures uncrosslinked low molecular weight fractions. Meeting the extractable limits set in us fda 21 cfr 177 1520 ensures that resin batches contain minimal soluble species that could migrate into fatty foods.
Xylene Soluble Fractioning
Non-crystalline polymer fractions are quantified by measuring xylene solubility at 25 degrees Celsius after full dissolution at elevated temperatures. Requirements in us fda 21 cfr 177 1520 restrict the amorphous content of polypropylene copolymers to preserve mechanical stiffness and thermal resistance in food packaging.
Resin Density Classification
Subparts of the regulation establish strict density ranges for low, medium, and high density polyethylenes. Testing resin density according to us fda 21 cfr 177 1520 dictates allowable food contact applications, temperature limitations, and maximum thickness specifications.
