Toxicological Threshold Risk Scoring for Non-Intentionally Added Substances in Recycled Polymers
Toxicological threshold scoring maps unidentified polymer migrates to Cramer exposure limits, mandating genotoxic screening below 0.00015 mg/kg food.
Antioxidant Degradation Products
Meaning
Chemical residuals formed when stabilisers react with heat and oxygen to protect a polymer during processing. Antioxidant degradation products are the resulting molecules after primary or secondary antioxidants have performed their scavenging functions. The presence of these substances signals that the original additives have been partially or fully depleted.
Processing Impact
High melt temperatures during extrusion accelerate the formation of these compounds as the additives sacrifice themselves to prevent chain scission. Antioxidant degradation products can alter the rheology of the resin if the breakdown occurs too rapidly. Melt flow changes make the material either too fluid or too viscous for the intended mould.
Analytical Detection
Identification of these substances requires liquid chromatography paired with sensitive detection to distinguish them from the parent molecules. Antioxidant degradation products often show up as unknown peaks in a migration profile during food safety audits. These peaks must be quantified to ensure they fall below the safety thresholds defined for non-intentionally added substances.
Material Stability
Retention of physical properties in recycled resins depends heavily on the concentration of these remaining breakdown molecules. When antioxidant degradation products accumulate in regrind, they indicate a lower level of future protection against environmental aging. A high concentration suggests the material has undergone multiple heat cycles and may require the addition of virgin stabilisers to remain viable for structural parts.
These residuals act as markers for the thermal history of the polymer.