Determining Non Target Screening Thresholds for Recycled Polyolefins
Determining non target screening thresholds requires deriving analytical detection limits from toxicological thresholds divided by GC and LC response uncertainty factors.
Synthetic Antioxidants
Meaning
Manufactured chemical compounds blended into polymer resins inhibit the auto-oxidation process triggered by heat, light, and mechanical stress. Within the plastics industry, synthetic antioxidants extend the lifespan of thermoplastic materials by preventing polymer degradation during both processing and environmental exposure. These additives are classified into primary scavengers that neutralize radicals and secondary hydroperoxide decomposers.
Stabilization Mechanism
Melt processing of polymers at high temperatures generates reactive radicals that react with atmospheric oxygen to initiate chain scission or cross-linking. Compounders add synthetic antioxidants to interrupt these reactions, preserving the melt flow index and tensile properties of the raw material. During extrusion and injection moulding, the additives act as sacrificial agents that oxidize before the polymer chains are damaged.
This stabilization is necessary when incorporating post-consumer recycle or regrind, as previously processed resin has already consumed its original stabilizer package. A balanced blend of primary and secondary stabilizers prevents yellowing, surface cracking, and brittle behavior in the finished product.
Sourcing Balance
Selection of these additives involves a trade-off between thermal performance, cost, and regulatory approvals for food contact. Molders must ensure that the additive levels on the resin datasheet match the demands of their processing window.
Processing Defect
Depletion of these protective compounds leads to rapid resin degradation during recycling or moulding, causing severe melt fracture and black speck contamination. This depletion results in a loss of physical properties and mechanical failure in the field.