Meaning
Tris(2,4-di-tert-butylphenyl) phosphite operates as a secondary organophosphite antioxidant that decomposes hydroperoxides formed during the high-temperature melt processing of thermoplastic resins. In polymer compounding, irgafos 168 protects polyolefins, polyamides and polycarbonate from thermal degradation, crosslinking and molecular weight loss during extrusion and moulding. The additive functions primarily inside the molten polymer phase during melt processing cycles.
It stops providing primary radical scavenging during low-temperature, long-term solid-state service life where phenolic antioxidants are required.
Synergistic Stabilization
Secondary phosphites react stoichiometrically with active hydroperoxide molecules to convert them into stable, non-radical alcohol derivatives while oxidizing into organophosphates. Compounders combine irgafos 168 with hindered phenolic antioxidants like irganox 1010 to provide comprehensive processing and thermal stabilization. This binary antioxidant blend prevents melt flow index drift during repetitive plastic extrusion.
Virgin polyolefin producers dose the additive at concentrations between five hundred and two thousand parts per million. Stabilizer synergy maintains polymer chain length across extreme thermal conditions.
Regrind Economics
Reprocessing plastic sprues, runners and post-industrial scrap degrades uninhibited polymer chains through thermal-mechanical shear stress. Adding supplemental irgafos 168 during scrap regranulation halts oxidation chains and preserves base resin melt properties. Without secondary antioxidant protection, polypropylene regrind suffers chain scission that increases melt flow and causes part flash during moulding.
Polyethylene regrind undergoes radical crosslinking that generates insoluble gels and high injection pressures. Restabilization protects regrind value and allows high scrap blend ratios.
Hydrolytic Limitation
Moisture exposure during long-term warehouse storage causes solid phosphite additives to hydrolyze into acidic phosphate degradation products. Hydrolyzed irgafos 168 loses antioxidant potency and creates severe corrosion on chrome-plated injection tooling and extruder screws. Active phosphite powder requires dry, sealed storage conditions to prevent premature environmental moisture uptake.
Converters verify additive purity through liquid chromatography before compounding critical packaging grades. Preserving chemical stability ensures reliable melt protection during high-temperature injection moulding. Secondary phosphite protection safeguards thermoplastic processability across multiple recycling loops.