Cyanic Esters
(Cyanate or Triazine Resins)

Properties and Applications

Cyanic esters (also called triazine or cyanate resins) are high performance thermosetting resins having reactive ring-forming cyanate groups (-O-C≡N). The cured resins form a 3D network of triazine rings and bisphenol. These so-called polycyanurates have a very high glass transition and decomposition temperature and are therefore, ideal for high temperature applications. Other useful properties include low water absorption, very little cure shrinkage, low dielectric properties, low flammability, and high tensile strength. On the downside, polycyanurates are very brittle, and thus need to be toughened. They are also rather expensive. To lower cost and to improve toughness, cyanic esters are often blended with (reactive) elastomers and other resins such as epoxies and novolacs. Well formulated Cyanic esters resin systems combine the toughness and adhesion properties of epoxies with the excellent thermal properties of toughened BMIs.

Cyanate ester resins are mainly used for high-performance structural composites and syntactic foams, mainly in the aerospace industry. They also find some uses in the electronic industry including electronic chip adhesives, encapsulants, and thermal interface materials. They are prefered over epoxy resins in demanding applications because they have greater thermal stability, superior dielectric properties, and much lower moisture absorption but are less frequently used due to their much higher price.

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