TEP Flame-Retardant Plasticizer for Rigid PIR Foam
DOBO Technical R&D TeamUpdated 9 on Nov 2026Oct 26, 2026
TEP (CAS 78-40-0) in rigid PIR foam: phosphorus-based flame retardancy with plasticizing effects, dosage trade-offs versus density and thermal conductivity, and guidance for classification testing.
TEP Flame-Retardant Plasticizer for Rigid PIR Foam
Can a single additive both plasticize and enhance flame retardancy in rigid PIR foam?A phosphorus-containing additive achieves both effects, which is why TEP (CAS 78-40-0) is used in highly flame-retardant flexible and rigid polyurethane foams and other systems requiring flame retardancy. Performance depends on dosage and system density; we recommend testing against your target flame-retardant rating and applicable test standard.
How phosphorus works in rigid foam
Rigid PIR foam is a closed-cell material with low thermal conductivity. Its fire performance depends on the balance between the isocyanate index, blowing agent, and additive package. Phosphorus-based additives act primarily in the gas phase by interrupting radical chain reactions in the flame, which reduces heat release and promotes self-extinguishing. Since triethyl phosphate is a liquid with inherent plasticizing properties, it can be metered into the polyol component and disperses without introducing solid fillers.
| Function | How TEP contributes | Verification checklist |
|---|---|---|
| Flame retardancy | Phosphorus behavior in the gas phase | Classification test required for the application |
| Plasticizing effect | Liquid additive reduces polyol viscosity | Mixing and metering behavior |
| Foam structure | Liquid additive disperses evenly | Cell structure and density |
| Thermal conductivity | Neutral to mild effect | Foam conductivity measurement |
| Dimensional stability | Dependent on Additive | Aging and Dimensional Stability Test |
Set Dosage
Dosage is typically expressed as parts per hundred of polyol (PHP) and is determined by flame-retardancy requirements, foam density, and the blowing agent system. Two factors must be balanced: increasing the additive level improves fire performance, but excessive levels can soften the foam, alter cell structure, and affect thermal conductivity.
| Variable | Increasing the level tends to | Check |
|---|---|---|
| Additive dosage | Improve flame-retardant performance | Classification test |
| Foam density | Modify the additive requirement | Density measurement |
| Isocyanate index | Influence of Char and Fire Behavior | Formula consistency |
| Blowing agent | Influence on cell gas and fire behavior | Processing trials |
| Polyol viscosity | Decrease | Metering and mixing |
Testing against the applicable standard
Fire performance claims are based on classification standards, not laboratory observations. Rigid foam is typically evaluated using the classification method required in the target market, and testing must be performed on panels manufactured under the intended process conditions. Additive suppliers can indicate how dosage adjustments affect performance, but the final classification result applies to the complete system.
Frequently asked questions
Is TEP a flame retardant or a plasticizer?Both. It is a phosphorus-based flame retardant that also functions as a plasticizer, making it ideal for applications requiring both flame resistance and viscosity control.
Can TEP also be used in flexible foam?Suitable for highly flame-retardant flexible and rigid polyurethane foams, as well as adhesives and coatings. Dosage varies by system.
What determines the final dosage?The required flame-retardant rating, foam density, and blowing agent system shall be confirmed via a trial using the intended formulation.
Does it affect the foam's thermal conductivity?The effect varies by level and cell structure; measure the conductivity of the finished foam rather than assuming it.
Request a sample and recommendation
Send us your polyol system and target flame-retardant rating. Our team will provide a 1kg complimentary TEP testing sample with current technical data, shipped worldwide via DHL or FedEx. Trial order MOQ is 1 MT; bulk shipments are loaded as 23 MT flexitank containers from Ningbo or Shanghai.
Related grade
TEP · TEP Triethyl Phosphate Flame Retardant
CAS78-40-0
Regulatory and standards references
The links below lead to official EU, US, and ISO sources for the compliance frameworks discussed on this page. DOBO does not control third-party content; the official text and regulations of the buyer's market take precedence.
- ECHA — Understanding REACHEU registration, evaluation, authorisation and restriction of chemicals (REACH), including the Candidate List of substances of very high concern.
- EUR-Lex — Directive 2011/65/EU (RoHS 2)Restriction on the use of certain hazardous substances in electrical and electronic equipment; Annex II lists restricted substances and their maximum concentrations.
- eCFR — 21 CFR 175.300US FDA regulations for resinous and polymeric coatings intended for repeated use as food-contact surfaces, including extraction testing conditions.
- ASTM — Plastic and plasticizer standardsASTM International publishes the test methods referenced in our TDS, including plasticizer sampling and chemical analysis, tensile properties, and heat-aging procedures.
- ASTM — Plastic and Plasticizer Testing StandardsASTM International has published the test methods referenced in the TDS, covering sampling and chemical analysis of plasticizers, as well as tensile properties and thermal aging procedures.
- ISO — ISO 10993-1Biological evaluation of medical devices — Part 1: Evaluation and testing within a risk management process, establishing the foundation for biocompatibility programs.
Request a 1 kg Free Sample & Full COA/TDS
Test TEP using your own formulation. The request below is pre-filled with the grade discussed in this whitepaper, along with the specification, documentation, and sample shipping confirmation.
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