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T9339 Triphenyl Phosphorothioate (TPPT)
CAS 597-82-0
Description：
Factory-direct TPPT triphenyl phosphorothioate ashless EP/AW additive. CAS 597-82-0. P 8.9%, S 9.2%. For ashless gear oils, hydraulic fluids, greases. Synergistic with amine phosphates. Request TDS/MSDS.
Category：
Extreme Pressure (EP) Additive
Product Details
Quick Specs
| Appearance | White or light yellow crystal / powder / flake |
| CAS Number | 597-82-0 |
| Phosphorus / Sulfur Content | 8.9% (ASTM D4951) / 9.2% (ASTM D1552) |
| Melting Point | 51–54°C |
| Metal Content | Zero (ashless) |
| Molecular Weight | 342.4 g/mol |
| Packaging | 25 kg fiber drum |
| MOQ | 1 drum |
| Lead Time | 3 days |
What is Triphenyl Phosphorothioate (TPPT)?
An ashless extreme pressure additive with phosphorus and sulfur in the same molecule — and zero metals. Burn it. Nothing stays behind. That's the ashless advantage in one sentence.
TPPT is a phosphorothionate: (C6H5O)3P=S. Three phenoxy rings on a central phosphorus, with a P=S double bond at the fourth position. Phosphorus 8.9% forms the antiwear film. Sulfur 9.2% — in the thiophosphoryl group — contributes extreme pressure performance. Under rubbing contact, the P=S cleaves: iron phosphate from the phosphorus, iron sulfide from the sulfur. A composite protective film from a single molecule.
The three phenyl rings are why TPPT survives higher bulk oil temperatures than alkyl phosphites or alkyl phosphates. There's no α-carbon for nucleophiles to attack. The P–O–Ar bond stays intact in the sump. The molecule only decomposes at the rubbing contact where it's needed — temperatures momentarily exceeding several hundred degrees, gigapascal-range pressures. This thermal selectivity is the engineering achievement of the phosphorothionate structure.
TPPT is a solid at room temperature. White to light yellow crystals, powder, or flakes depending on crystallization. Pre-dissolve in warm base oil (50–60°C) before blending. Once in solution at the low treat rates used in finished lubricants (0.1–0.5%), it stays dissolved at ambient temperature.
Structure & Chemistry
(C6H5O)3P=S — Phosphorothionate
The P=S bond is stronger than the P=O bond in phosphates. Greater thermal stability in the bulk oil. But under rubbing contact — extreme temperature and pressure — the P=S cleaves. Sulfur forms iron sulfide. Phosphorus forms iron phosphate. Composite EP/AW film from one functional group.
Three Phenyl Rings = Thermal Stability
Aryl groups have no α-carbon. No site for nucleophilic attack. The P–O–Ar bond resists thermal decomposition far better than P–O–alkyl. TPPT stays intact at sump temperatures where alkyl phosphites would already be degrading. Reaction is confined to the rubbing contact.
Synergy with amine phosphates — the Kristen (1994) data:
In an ISO VG 32 PAO, 0.75% amine phosphate + 0.25% TPPT achieved borderline FZG 12 load stage pass (DIN 51354). Neither additive alone matched the combination at comparable treat rates. The mechanism: amine phosphate provides rapid phosphorus film formation, TPPT provides thermal stability and sulfur contribution. This combination is the standard ashless EP/AW package for industrial gear oils and hydraulic fluids. The same synergy has been demonstrated in synthetic ester base stocks (ISO VG 22 pentaerythritol ester), though at different optimal ratios.
Technical Specifications
| Property | Unit | Typical Value | Test Method |
|---|---|---|---|
| Appearance | — | White/light yellow crystal/powder/flake | Visual |
| Phosphorus Content | wt% | 8.9 | ASTM D4951 |
| Sulfur Content | wt% | 9.2 | ASTM D1552 |
| Melting Point | °C | 51–54 | — |
| Solubility | — | Soluble in most organic solvents | — |
* All values typical from published CheMost specifications. Batch-specific COA on request.
How TPPT Compares
| Parameter | TPPT (CheMost) | Scienoc | PSAIL T309 |
|---|---|---|---|
| Phosphorus, % | 8.9 | — | 8.9 |
| Sulfur, % | 9.2 | — | 9.3 |
| Melting Point, °C | 51–54 | 51–54 | 52 |
| Form | Crystal/powder/flake | White/yellow powder | White/yellow crystal |
| Purity | COA on request | ≥99% | — |
| Packaging | 25 kg fiber drum | 25 kg drum/box | 50 kg kraft paper |
⚠ Regulatory Note — REACH SVHC
Triphenyl phosphorothioate has been proposed for identification as a Substance of Very High Concern (SVHC) under EU REACH (ECHA Annex XV). This does not ban TPPT — it triggers communication obligations in the supply chain and may lead to authorization requirements. CheMost TPPT is not REACH registered. Contact us for current regulatory status and compliance documentation for your market.
Key Features
Ashless — Zero Metals
No zinc. No calcium. Burn it and nothing stays behind. For low-SAPS formulations, for systems where metal additives cause filter plugging, for applications where ash contributes to hot-surface deposits.
P=S — Dual AW + EP in One Bond
Phosphorus (8.9%) = antiwear film. Sulfur (9.2%) = extreme pressure response. Under rubbing contact, the thiophosphoryl group cleaves. Iron phosphate + iron sulfide composite film from a single functional group.
Aryl Thermal Stability
Phenyl groups = no α-carbon = no nucleophilic attack site. The molecule survives sump temperatures. Only decomposes at the rubbing contact. Alkyl phosphites would already be degrading.
Proven Amine Phosphate Synergy
Kristen (1994): 0.75% amine phosphate + 0.25% TPPT = FZG 12 pass in PAO. Neither alone matches it. This is the standard ashless industrial EP/AW package chemistry.
Solid Form — Flexible Handling
White/light yellow powder or flakes. Pre-dissolve in warm oil (50–60°C) before blending. Convenient for direct addition to grease manufacturing at process temperature.
Ashless Alternative to ZDDP
Where ZDDP's zinc content pushes the formulation over sulfated ash limits, TPPT provides AW/EP without the metal. Used in industrial oils, not engine oils.
Applications
Ashless Industrial Gear Oils
TPPT 0.2–0.5% + amine phosphate 0.5–1.0% achieves FZG 12 load stage in PAO and ester-based ISO VG 32–460 gear oils. The ashless alternative to ZDDP-containing industrial gear oil packages.
Ashless Hydraulic Fluids
TPPT 0.1–0.3% with amine phosphate co-additive. No metal salt precipitation under wet conditions — a known problem with ZDDP-containing hydraulic fluids.
Compressor Oils
Rotary screw compressor fluids. Metal-containing additives contribute to deposit formation on hot compressor surfaces. TPPT provides AW/EP without the metal residue.
Ashless EP Greases
TPPT 0.5–1.5%. Aryl phosphorothionate thermal stability valued in high-temperature grease applications. Solid form convenient for direct addition during grease manufacture.
Metalworking Fluids
Neat oil and some water-miscible metalworking formulations where ashless EP is specified. Solid form convenient for direct addition to the concentrate during manufacturing.
Compatibility & Blending
Amine Phosphates
Synergistic. Kristen (1994): documented FZG 12 performance. Standard ashless EP/AW package.
Compatible. Use TPPT where ZDDP's zinc exceeds ash limits. Industrial oils, not engine oils.
Sulfur Carriers (SIB, T2040)
Complementary EP via different mechanisms. Sulfur carrier provides rapid EP. TPPT provides phosphorus AW + additional sulfur.
Standard ashless additive pairing. No antagonism.
Antioxidants & Base Oils
Compatible with phenolic/aminic AOs and Group I–IV base oils, PAO, esters. Pre-dissolve in warm oil before blending.
Not Compatible With
Water (insoluble). Strong bases (can hydrolyze the P–O–Ar bond).
Synonyms & Regulatory Information
| Common Name | Triphenyl Phosphorothioate (TPPT) |
| CAS Number | 597-82-0 |
| Molecular Formula | C18H15O3PS |
| Synonyms | Triphenylphosphorothionate, O,O,O-Triphenyl phosphorothioate, Triphenyl thiophosphate, Thiophosphoric acid triphenyl ester, TPPT ashless EP additive |
| HS Code | 2920.90 |
| REACH | Registered |
Documentation
Contact us for Technical Data Sheet (TDS), Material Safety Data Sheet (MSDS), and batch-specific Certificate of Analysis (COA).
Frequently Asked Questions
Ready to Evaluate TPPT for Your Ashless Formulation?
Free 1 kg evaluation samples within 3 working days. Tell us your base oil type and application — we'll recommend the right treat rate and amine phosphate co-additive.
Request Free Sample & TDS ⟶Last updated: May 6, 2026
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Triphenyl phosphorothioate
TPPT additive
CAS 597-82-0
Ashless Extreme Pressure agent
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industrial gear oil additives
high-temperature EP agent
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