Pentaerythritol phosphate (PEPA), CAS 5301-78-0, is a white powder phosphorus-based char former for halogen-free intumescent flame-retardant (IFR) systems. With a phosphorus content of 16-17.2% and a melting range of 195-210 deg C, PEPA combines an acid source and a carbon skeleton in one molecule, so it replaces part of the pentaerythritol or dipentaerythritol in a classical ammonium polyphosphate / melamine / polyol package while improving water resistance and char yield. PolyBlueChem supplies PEPA as a fine white powder with per-batch COA and SDS.
Specifications
| Property | Specification |
|---|---|
| Appearance | White powder |
| Phosphorus content (%, as P) | 16.0 – 17.2 |
| Melting point (deg C) | 195 – 210 |
| Loss on drying (%) | Max 0.5 |
| Packaging | 25 kg net, inner PE liner; 500-1000 kg jumbo bags on request |
Basic Information
| Chemical name | Pentaerythritol phosphate (phosphate ester of pentaerythritol) |
| Abbreviation | PEPA |
| CAS number | 5301-78-0 |
| Functional class | Phosphorus char former / acid source for intumescent systems |
| Appearance | White powder |
| Phosphorus content | 16 – 17.2% |
| Melting range | 195 – 210 deg C |
| Moisture | Max 0.5% (loss on drying) |
| Halogen content | None added – suitable for halogen-free formulations |
How It Works
On heating, PEPA releases phosphoric and polyphosphoric acid species that dehydrate the polymer and the co-additives into a carbonaceous char. Because the phosphorus unit is bonded to a pentaerythritol backbone, the same molecule supplies both the acid catalyst and part of the carbon framework, which is why PEPA raises char yield and reduces dripping at lower total additive loading than a phosphate-plus-polyol combination. The expanding char layer acts as a heat sink and a mass barrier, cutting heat release rate and smoke in the flame zone.
Compared with pentaerythritol and dipentaerythritol, PEPA is far less water-soluble. That matters in humid or outdoor service and in water-borne coatings, where a soluble polyol can migrate, bloom or be extracted, leaving the coating unable to intumesce after ageing.
Typical Applications
- Halogen-free intumescent flame retardants for PP, PE, TPO and glass-fibre composites – as the char former in an APP / melamine / PEPA package.
- Low-smoke zero-halogen (LSZH) cable compounds – cable sheathing and insulation where acid gas and smoke density are restricted.
- Intumescent fire-retardant coatings for structural steel, wood and cable trays, in both solvent-borne and water-borne systems.
- Rigid and flexible PU foams – phosphorus char promotion with reduced halogen demand.
- Coatings crosslinking and adhesion – phosphate ester groups improve adhesion to metal substrates and act as a cure catalyst in stoving systems.
- Metal surface treatment – phosphate-ester based corrosion and paint-adhesion promoters.
Formulation Notes
| Point | Guidance |
|---|---|
| Role in the package | Char former plus acid source; normally used together with ammonium polyphosphate and a nitrogen source such as melamine |
| Starting loadings | Typically 3 – 10 phr within a 20 – 30 phr intumescent package – confirm by cone calorimeter or UL-94 trial in your own system |
| Drying | Dry before compounding when loss on drying approaches the 0.5% limit; moisture hydrolyses phosphate esters and reduces char quality |
| Processing window | Compound below the decomposition range; standard twin-screw profiles for PP/PE filled compounds are suitable |
| Co-additives | Zinc borate, talc or zeolite-type synergists can be used to tune char strength and smoke |
Packaging, Storage and Documentation
Supplied in 25 kg net bags with an inner PE liner, or 500-1000 kg jumbo bags for compounders. Store in a dry, ventilated area: the material is hygroscopic and caking is the main storage risk, not thermal hazard. Each batch ships with a certificate of analysis covering appearance, phosphorus content, melting range and loss on drying; SDS is available in English. Export packing, palletisation and shipping documents are arranged per order.
Related reading
- Pentaerythritol phosphate (PEPA): properties, production and applications
- PEPA in intumescent fire-retardant coatings
- PEPA vs dipentaerythritol vs ammonium polyphosphate
- Melamine in flame retardants and intumescent systems
FAQ
What is the CAS number of pentaerythritol phosphate? CAS 5301-78-0.
Can PEPA replace pentaerythritol in an IFR system? In many PP and PE systems it can replace part or all of the polyol char former; because it carries both acid and carbon functions, the APP level is usually re-balanced. Confirm the ratio by a cone calorimeter or UL-94 trial.
Is PEPA halogen-free? Yes – it is a phosphorus-based char former with no halogen added, which is why it is used in halogen-free and LSZH formulations.
How is PEPA supplied? White powder in 25 kg bags with an inner liner, or jumbo bags on request, each batch with COA and SDS.
Contact PolyBlueChem for specifications, samples and quotations.
