Tiangang® AO-168

What it is

Tiangang® AO-168 is a antioxidant. Antioxidants come in two roles. Primary antioxidants (hindered phenols) trap radicals and stop the chain; secondary antioxidants (phosphites) decompose hydroperoxides. Used together they cover both processing and service life. Product identifiers: chemical name Tris(2,4-di-tert-butylphenyl)phosphite; CAS 31570-04-4; molecular weight 647; melting point 185.

Technical data

Molecular weight around 647 — mid-range: a workable balance between diffusion speed and retention.Melting point 185 °C — the processing window needs to reach above it for uniform dispersion.

Where it is used, and at what loading

Polyolefins are the main field, followed by polyacetal, polyamide, polyester, PVC, polystyrene and elastomers. The higher the melt temperature and the longer the residence time, the more the system needs.

Figures above are typical industry ranges, not guaranteed values. The actual loading depends on wall thickness, design life and the other additives in the system, and should be established by a loading ladder on the real formulation.

Choosing between similar grades

Three things decide the choice for AO-168: molecular weight and volatility, basicity, and compatibility with the other components in the system. Grade 168 is the phosphite partner: it decomposes hydroperoxides and has no radical-scavenging action of its own, so it must be paired with a primary antioxidant.

Frequently asked questions

Do primary and secondary antioxidants have to be used together?

In most cases yes. The primary handles radicals, the secondary handles hydroperoxides; using only one leaves the other degradation path open. Blends such as B215, B225 and B277 pre-mix the two, which removes weighing error at the line.

Why does low initial colour matter?

Some phenolic antioxidants form quinoid structures during processing and yellow the part. Fibre, film and light-coloured articles are most sensitive. Low-colour grades suppress that side reaction at the source.

Can antioxidants and light stabilizers interfere?

Yes, mainly through acid-base conflict. Acidic components (some phosphites, halogenated flame retardants) deactivate highly basic HALS. We look at both sides of the balance and switch to a low-basicity HALS where needed.

The figures and guidance above follow Tiangang's published technical material and common industry practice. For a specific formulation, refer to the batch COA and the technical agreement between the parties.

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