Meaning
Branched-chain saturated hydrocarbons containing twelve or more carbon atoms represent a distinct class of paraffinic compounds found in polymer lubricants and mineral oil residues. These branched structures, also known as long chain iso-alkanes, possess lower melting points and higher volatilities than their linear counterparts of equivalent molecular weight. They are commonly used as process aids or plasticizers in various polymer formulations to improve melt flow and processability.
Their presence in plastic packaging must be carefully monitored because they can migrate into packaged goods and affect product safety.
Chemical Property
The methyl branching along the hydrocarbon chain disrupts the crystal packing of these molecules, resulting in lower viscosity and greater fluidity. This structural characteristic makes them highly effective as external lubricants, reducing the friction between the polymer melt and the metal walls of the extruder. However, their branched nature also makes them more resistant to chemical and biological degradation than straight-chain alkanes.
This persistence necessitates rigorous testing of packaging materials to ensure that these compounds do not accumulate in the food simulant during migration studies.
Extraction Analysis
Quantifying these branched paraffins in polymer matrices requires extraction with non-polar solvents followed by gas chromatography analysis. Because of the numerous possible isomers, they often elute as a broad, unresolved hump in the chromatogram rather than as individual, sharp peaks. This complex mixture requires sophisticated integration techniques and the use of mass spectrometry to differentiate them from other hydrocarbon contaminants.
The use of specific diagnostic ions helps in identifying the branched structures within the complex chromatogram.
Migration Standard
Regulatory agencies establish specific migration limits for mineral oil saturated hydrocarbons, which include these branched alkanes, to protect consumer health. Importers and converters of plastic packaging must verify that the total migration of these substances remains below the accepted limits, typically set at a few milligrams per kilogram of foodstuff. Compliance is achieved by selecting high-purity polymer grades and optimizing the processing parameters to minimize the concentration of volatile hydrocarbons in the finished article.
This control ensures that the packaged product remains safe and untainted.
