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Description and features

Catonium ETPI (Ethyltriphenylphosphonium Iodide) is a white to off-white crystalline powder, its chemical formula is C20H20P. ETPI is a quaternary phosphonium salt mainly used for the advancement and / or curing of phenolic based epoxy resins and thermosetting powder coatings. It can also be used in organic synthesis as a wittig reagent and as a phase transfer catalyst in the production of fluoroelastomers . This material is highly soluble in water and polarizable solvents.

Ethyltriphnylphosphonium Iodide is also known as ETPI, ETPPI and TPEP-I.

Compared to amines, imidazoles and quaternary ammonium salts CatOnium ETPI features considerable better latency and thermal stability. Further it offers a low odor, minimal color formation and controlled reactivity. It decreases or eliminates side reactions and creates longer, straighter chain epoxy molecules which have a sharp molecular weight distribution.


Europe and United States: Provided CatOnium ETPI is on stock in our local warehouses our lead time is about one week if delivered in 25 KG drums.

Canada,  South America,  South Africa and other markets can also be served, please contact our sales department for more details.

➔ Limited available in the European Union as this product has not been REACH registered (yet).

Product Identification

CAS number4736-60-1
EC number225-245-2
HS code2931 39 90


AppearanceWhite to off crystal powder
Assay≥ 99.00 %
Loss on drying≤0.20 %
Triphenyl phosphine≤ 0.50 %


CatOnium ETPI (Ethyltriphenylphosphonium Iodide) is being used in fluoroelastomers, thermosetting powder coatings and phenolic based epoxy resins.


Available packaging: 25 KG.
Special packaging is available on request.


Store Ethyltriphenylphosphonium Iodide in a cool, dry and well-ventilated area and in line with  legal requirements.

Keep ETPI away from heat sources and oxidizing agents.


A Material Safety Data Sheets (MSDS) is available for CatOnium ETPI and all other products supplied by Vesta Chemicals BV.

An MSDS describes the hazards of a product and explains how a product can be safely handled, used and stored. Besides it provides important regulatory and emergency response information for the purchased product.

Molecular and structural information

Molecular formulaC20H20IP
Molecular weight418.26 g/mol
Smiles notation [P+](c1ccccc1)(c1ccccc1)(c1ccccc1)CC.[IH-]
Chemical formula 4736-60-1 | Ethyltriphenylphosphonium Iodide

Physicochemical information

Boiling point> 360 ºC
Relative density @ 20 ºC 1.47 g/cm3
Flash pointNot tested
Melting point170 °C
Partition coefficient (log Pow)0.324 @ 25 ºC
Solubility in water7.84 g/L (20.1O ºC)
Vapor pressure 0 Pa @ 25 ºC

Ethyltriphenylphosphonium Iodide | CAS: 4736-60-1 | Disclaimer. This information is supplied solely for informational purposes and Vesta Chemicals bv makes no guarantees or warranties, either expressed or implied, with respect to the accuracy and use of this data. All product warranties and guarantees shall be governed by the Standard Terms of Sale. Nothing in this document is legal advice or is a substitute for competent legal advice.