Analytical Techniques for Non Intentionally Added Substances in Recycled Plastics
Non-target HRMS screening combined with toxicological threshold evaluation provides the empirical basis for verifying recycled plastic safety before market entry.
Bht Quinone
Meaning
Antioxidant degradation product represents the oxidized form of butylated hydroxytoluene commonly found in polymer additives. When this yellow to brown substance develops within plastic resins, it indicates that the stabilizer package has reached its functional limit.
Resin Stability
Processing heat histories accelerate the conversion of phenolic stabilizers into this specific byproduct. High melt temperatures during extrusion force the migration of these species to the surface of the part. Discoloration manifests as yellowing or dark streaking within the molded component when the chemistry shifts.
Material Performance
Virgin resin suppliers maintain strict limits on residual antioxidant concentration to prevent premature aging. Moulders monitor color shifts as a proxy for the total thermal history of a batch. Regrind addition introduces existing quinone levels into fresh melt streams, effectively depleting the remaining active stabilizer pool.
Higher degradation thresholds allow for more passes through the injection unit before structural failure occurs.
Additive Calibration
Quantification of this molecule relies on liquid chromatography to measure the exact degree of stabilizer exhaustion. Precise dosing of fresh antioxidants counteracts the presence of established degradation products in secondary material streams. Calibration sets the allowable shift in the yellow index during extended machine downtime or heat soaking cycles.
Standard laboratory testing validates the effectiveness of the additive package against oxidative stress across varying shear intensities.