Technical Specifications
| Property | Unit | Typical Value | Test Method |
|---|---|---|---|
| Appearance | Light yellow liquid | Visual | |
| Density at 20 °C | kg/m³ | 910 | ASTM D4052 |
| Flash Point | °C | 130 | ASTM D93 |
| Free Phenol | % | 0.5 | GC |
| Freezing Point | °C | -30 | ASTM D97 |
* Typical values from batch production. Batch-specific COA available on request.
Technical content reviewed by the CheMost additives team · Specifications last reviewed
Molecular Structure
Composition · binary phenol blend
Blend: BHT C₁₅H₂₄O (CAS 128-37-0) + 2,6-di-tert-butylphenol C₁₄H₂₂O (CAS 128-39-2)
AO52 is a binary blend of two hindered phenols — 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,6-di-tert-butylphenol — kept liquid down to −30 °C for easy dosing.
What Is a Mixed Phenols Antioxidant (AO52)?
CheMost-AO52 is a liquid mixed phenolic antioxidant — a blend of two hindered phenols, 2,6-di-tert-butyl-4-methylphenol (BHT, CAS 128-37-0) and 2,6-di-tert-butylphenol (CAS 128-39-2). Because it is a deliberate mixture rather than a single compound, it has no single CAS number; the data sheet specifies it by composition and properties, and it is supplied as a pourable, pale-yellow-to-red liquid that mixes easily.
Both components are hindered-phenolic primary antioxidants — the phenolic –OH donates a hydrogen to a peroxy radical, breaking the oxidation chain. The reason for blending them is physical, not chemical: BHT on its own is a solid that must be melted or dissolved, while mixing it with liquid 2,6-di-tert-butylphenol depresses the freezing point to −30 °C. The result keeps the oxidation performance of BHT but in a form that pours and meters cleanly, even in cold blending.
The data sheet positions AO52 for low-end industrial oils — particularly turbine oils — to significantly improve oxidation resistance. For hotter or longer-drain duty, formulators step up to a high-molecular-weight phenol (AO135) or an aminic antioxidant (AO57).
How AO52 Works
Two hindered phenols, one mechanism
Both BHT and 2,6-di-tert-butylphenol scavenge free radicals by donating a hydrogen from the hindered phenolic –OH, halting the oxidation chain — the primary-antioxidant route.
Liquid down to −30 °C
Blending solid BHT with liquid 2,6-di-tert-butylphenol depresses the freezing point to −30 °C, so the antioxidant stays pourable and easy to dose in cold conditions — no melting step.
BHT-comparable protection
The data sheet reports antioxidant performance comparable to BHT, with the practical advantage of a liquid that meters cleanly into the blend.
Low free phenol
At 0.5% free phenol the blend is well-defined and consistent, suited to repeatable dosing in industrial-oil production.
Antioxidant Types Compared — Where AO52 Fits
Lubricant antioxidants split into aminic and phenolic primary types plus liquid/solid forms. The table places AO52 against CheMost’s other antioxidant grades so you can pick by temperature, form and handling. All figures are from each grade’s data sheet.
| Grade | Class | Form | Key spec | Temperature niche |
|---|---|---|---|---|
| AO52 (this page) | Phenolic (mixed blend) | Liquid | Free phenol 0.5% · freezes −30 °C | Low-end industrial / turbine |
| BHT | Phenolic (simple) | Solid | Purity 99.9% | Low–moderate temperature |
| AO135 | Phenolic ester (HMW) | Liquid | 100% active | High-temp, low-volatility |
| AO57 | Aminic (alkylated diphenylamine) | Liquid | N 4.58% · TBN 198 | High-temperature primary AO |
AO52 is essentially liquid BHT: choose it over solid BHT when pourable handling matters; step up to AO135 or AO57 for high-temperature service.
Applications
CheMost-AO52 is used as the pourable phenolic antioxidant in formulations targeting the duties below:
Turbine oils
The data sheet’s headline application — AO52 significantly improves the oxidation resistance of turbine oils, dosed as an easy-handling liquid.
Low-end industrial oils
Cost-effective oxidation protection for general and low-end industrial oils where a pourable phenolic is preferred over solid BHT.
Circulating & cold-blend operations
Its −30 °C freezing point keeps the antioxidant fluid for circulating oils and for blending plants operating in cold conditions.
Finished-oil performance approvals belong to the fully formulated oil, not to an individual antioxidant component.
Treat Rate
The data sheet specifies the product but not a per-application dosage, so the figures below are indicative, derived from the chemistry and our formulating experience — confirm the final level.
First-order estimate. As a liquid phenolic antioxidant, AO52 is used at roughly 0.05–1% (like BHT), dosed to the oxidation target. The liquid form meters cleanly at ambient temperature and stays fluid to −30 °C, so there is no melting or dissolving step.
For broader temperature coverage AO52 can be paired with an aminic antioxidant such as AO57 (heterosynergism); where higher-temperature persistence is needed, a high-molecular-weight phenol such as AO135 supplements it. The exact level depends on the oxidation target, the base oil and the rest of the package.
Treat rates are indicative, not fixed dosages. CheMost can provide formulation and treat-rate support on request.
Formulating With AO52 — Complementary Additives
Solid BHT
AO52 is the liquid counterpart of BHT; the two share the same phenolic chemistry, so the choice between them is handling (pourable liquid vs solid granules) and cost, not mechanism.
Aminic antioxidant (AO57)
Adding an aminic gives heterosynergism — phenol and amine trap radicals by different routes and regenerate one another, extending protection to higher temperature than the phenols reach alone.
Rust inhibitors
Turbine and circulating oils combine the antioxidant with a rust inhibitor to protect ferrous surfaces — the two are the backbone of a long-life industrial-oil package.
Metal deactivator (BTA)
A metal deactivator passivates copper and yellow metals that would otherwise catalyse oxidation, sparing the phenolic reserve.
Documentation, Qualification & Regulatory Support
Standard documentation — Certificate of Analysis (COA, per shipment), Technical Data Sheet (TDS) and Safety Data Sheet (SDS, GHS/CLP) — is provided. The full TDS is available on request rather than as a public download. Additional support is available on request:
Regulatory documentation
REACH, TSCA and country-specific market-registration documentation support available on request.
Third-party inspection
SGS / Intertek / BV pre-shipment inspection can be arranged on request.
Custom grades & packaging
Custom packaging and grades on request.
Formulation support
Antioxidant-system and treat-rate guidance from our technical team.
Packaging & Supply
CheMost-AO52 is stocked and shipped worldwide, with a typical lead time of 1–15 days and a 36-month shelf life at ambient temperature. Samples and quotations are answered within 12 hours.
Packaging
190 kg metal drum · 900 kg IBC tank.
Minimum order
1 drum / 1 IBC — contact us for your quantity.
Incoterms
FOB · CIF · EXW, to suit your freight arrangement.
Loading ports
All major Chinese ports.
Frequently Asked Questions
What is a mixed phenols antioxidant?
AO52 is a liquid blend of two hindered phenols — 2,6-di-tert-butyl-4-methylphenol (BHT, CAS 128-37-0) and 2,6-di-tert-butylphenol (CAS 128-39-2). Both scavenge free radicals; blending them gives a pourable liquid (freezes at −30 °C) with oxidation performance comparable to BHT but easier to handle.
Does AO52 have a single CAS number?
No. Because it is a deliberate mixture of two distinct phenols, it has no single CAS number — the components are CAS 128-37-0 (BHT) and CAS 128-39-2 (2,6-di-tert-butylphenol). It is specified by composition and properties on the data sheet.
Is AO52 just liquid BHT?
Effectively, yes — it delivers BHT-comparable phenolic antioxidancy but stays liquid down to −30 °C, so it meters cleanly without melting solid BHT. If you prefer the solid, see CheMost-BHT.
What treat rate should I use?
As a liquid phenolic antioxidant it is typically used at about 0.05–1% (like BHT), dosed to the oxidation target, and can be paired with an aminic such as AO57 for broader temperature coverage. The exact level depends on the base oil and the rest of the package; our technical team can assist.
How is it supplied, and how fast can I get a sample?
It is supplied as a pale-yellow liquid in 190 kg metal drums and 900 kg IBC tanks with a 36-month shelf life, and shipped worldwide. As a manufacturer and sourcing partner (Est. 2013), CheMost answers sample and quotation requests within 12 hours.