- ▸ Halogen-free flame retardant and viscosity depressant for unsaturated polyester resins and PU foams
- ▸ Reactive solvent and catalyst carrier in polymer and coating systems
- ▸ Flame-resistance additive for cellulosic and resin formulations
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
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Triethyl phosphate (TEP) is a low-viscosity, halogen-free trialkyl phosphate ester that doubles as a flame retardant, a viscosity-reducing reactive diluent, a solvent and a chemical intermediate. Its low viscosity and high phosphorus content make it a go-to halogen-free phosphorus source for unsaturated polyester and polyurethane systems. Identity: PubChem / CAS 78-40-0.
What it is
Triethyl phosphate (CAS 78-40-0) is a clear, low-viscosity liquid trialkyl phosphate. It is fully halogen-free and widely used wherever a mobile, high-phosphorus liquid is needed — as a flame retardant, a viscosity cutter, a solvent and a building block.
How it performs in fire
As a phosphorus-based flame retardant it acts mainly in the condensed phase, promoting char that shields the polymer, with some vapor-phase activity. Because it is so low in viscosity, it lowers the viscosity of the resin at the same time, which is valued in unsaturated polyester (UPR) and casting systems where a separate diluent would otherwise be needed.
Applications
TEP is used as a halogen-free flame retardant and viscosity reducer in unsaturated polyester resins, polyurethane foam and intumescent coatings, and separately as a solvent and a chemical intermediate (it is a building block and catalyst/curing component in several processes). For higher-temperature or solid-FR needs compare TPP and TMP.
Forms, grades and handling
TEP is supplied as a clear, low-viscosity liquid in drums, IBCs and bulk. Properties are typical reference values; the Certificate of Analysis (CoA) for the lot you buy governs. Handle per the current Safety Data Sheet (SDS), and confirm regulatory status and restrictions for your market and end use — flame-retardant regulation evolves. Each lot ships with CoA, TDS and SDS.
Bulk supply and RFQ
RawSource sources Triethyl Phosphate direct from producers in bulk, with CoA, TDS and SDS per lot. Tell us your polymer or system, the fire test you must pass, your maximum loading, and whether the application must be halogen-free, and we will quote the right grade. See the full range and selection logic in the flame retardants guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical / class | Flame retardant / viscosity reducer / solvent (trialkyl phosphate) |
| Flame-retardant type | Halogen-free trialkyl phosphate |
| Role in fire performance | Vapor/condensed phase; phosphorus source |
| CAS Number | 78-40-0 |
| Molecular Formula | C6H15O4P |
| Molecular Weight | 182.15 g/mol |
| Handling | Refer to the current SDS |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU):
- EC number: 201-114-5
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is triethyl phosphate (TEP) used for?
Triethyl phosphate (CAS 78-40-0) is a halogen-free trialkyl phosphate used as a flame retardant and viscosity reducer in unsaturated polyester resins, polyurethane foam and intumescent coatings, and separately as a solvent and chemical intermediate. Its low viscosity and high phosphorus content make it a versatile halogen-free phosphorus source.
Is triethyl phosphate a halogen-free flame retardant?
Yes — TEP contains no bromine or chlorine. It is a phosphorus-based, halogen-free flame retardant that works mainly by promoting char in the condensed phase.
What is the CAS number and formula of TEP?
Triethyl phosphate is CAS 78-40-0, molecular formula C6H15O4P, molecular weight 182.15 g/mol (PubChem CID 6535). The CoA documents the grade.
How is bulk triethyl phosphate supplied and quoted?
RawSource supplies triethyl phosphate in bulk with CoA, TDS and SDS per lot. Pricing is quote-based on grade and volume; submit an RFQ with your target quantity, polymer/system and the fire test you must pass.
What is the REACH and TSCA regulatory status of Triethyl Phosphate (TEP)?
Triethyl Phosphate (TEP) (CAS 78-40-0) is subject to U.S. TSCA Inventory requirements; supplying it into the EU requires valid REACH registration ((EC) No 1907/2006). RawSource cannot verify a third-party supplier's registrations — buyers should require documented TSCA and REACH compliance for their jurisdiction and volume (EC 201-114-5).