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Epoxy Curing Catalysts

Phosphonium Ionic Liquids - Uses As Epoxy Curing Catalysts

Epoxy resins are mainly used in coatings, electronics, composite materials and as additives in powder coatings. Epoxies must undergo curing, a process that typically requires catalysts, to satisfy process and application requirements. Selecting the proper epoxy curing catalysts can accelerate the curing process and helps ensure the epoxy resin system possesses necessary properties, such as: 

  • Long pot life
  • High chemical resistance
  • Excellent clarity
  • Superior electrical properties
  • High thermal stability 
  • Good mechanical properties


As an ionic liquid supplier, Syensqo offers a unique set of phosphonium salts that act as latent, soluble catalysts and curing agents for both neat epoxies and epoxy anhydride systems. CYPHOS® phosphonium salts deliver optimal performance to the epoxy resin system in heat-cured applications, such as pultrusion and filament winding. Our ionic liquids provide increased hydrophobicity in resin systems, and offer a cost-effective and safer alternative to traditional boron Lewis acids, imidazoles and dicyanamides (DICY).

Our Epoxy Anhydride Resin Solutions

CYPHOS® IL 169 is an ideal latent catalyst for two-component epoxy anhydride resin systems used in applications such as pultrusion, filament winding and high-power electric needs. This low-viscosity phosphonium salt has a wide liquid range and is non-volatile, allowing for easy handling and processing. Latent at room temperature when mixed with epoxides, unlike amines, CYPHOS® IL 169 supports premixing and storage of “pre-catalyzed” systems. Furthermore, it is soluble in most DGEBA resins. Epoxy anhydride systems catalyzed with CYPHOS® IL 169 have shown substantial clarity improvement compared to systems catalyzed with imidazole-based EMI24CN. In lab testing of cured resin systems, imidazole-based catalysts demonstrated significant yellowing when compared with CYPHOS® IL 169.


cyphos test data


Key advantages of CYPHOS® IL 169:

  • Latency (allowing premixing) 
  • Fast curing at elevated temperature 
  • High glass transition temperature (Tg) 
  • Cured epoxy resin systems with excellent clarity and increased hydrophobicity   
  • Continuous process compatibility 
  • Long period of stability (one year under normal conditions)


Syensqo is a large-scale ionic liquid supplier, providing a broad range of CYPHOS® phosphonium ionic liquids, which are effective for epoxy resin curing and as phase transfer catalysts for the advancement process. 


Typical properties of phosphonium ionic liquids

  1. Liquid at room temperature 
  2. Thermally and chemically stable
  3. Wide electrochemical window 
  4. Low vapor pressure
  5. Tunable hydrophobicity and inert to atmosphere 


Availability of Syensqo's epoxy curing catalysts

CYPHOS® IL 169 is commercially available from Syensqo for sampling and testing in applications. It is currently offered in drums (204 kgs) and pails (20 kgs). Smaller volumes can be requested.