ABSTRACT
Polycyanurates (PCN) posses a variety of excellent thermal and good mechanical properties, which determine their use in high performance technology (e.g. as matrixes for composites for highspeed electronic circuitry and transportation). For electronics market, attractive features ofPCN are low dielectric loss characteristics, dimensional stability at molten solder temperatures (220-270°C), high purity, inherent flame-inhibition (giving the potential to eliminate bromated flame retardants) and excellent adhesion to conductor metals at temperatures up to 250°C [I]. From the end of 1970s cyanate ester resins have been used with glass or aramid fibers in high-speed multilayer circuit boards and this remains their primary application. Several reviews [2-6] collecting the numerous publications (papers and patents) in the field of PCN synthesis, processing, characterization, modification and application appeared in 1990s. Additionally to this fact, as well as conventional .FR-4 diepoxides the cyanate ester laminates retain the desirable (ketone) solution processing characteristics and the ability to be drilled making possible employment of them in printed circuitboard manufacture. During the last two decades, aerospace composites were evolved into damage-tolerant primary and secondary structures utilizing both thermo-set and thermo-plastic resins. PCN homopolymers develop approximately twice fracture toughness of multifunctional epoxies while qualifying for service temperatures of at least 150°C, intermediate between epoxy and bismaleimides capabilities. PCN were flown in radomes prototype and high gain antennae with possible applications in primary and secondary structures of the High Speed Civil Transport (HSCT) and European Fighter Aircraft. PCN were also qualified for satellite truss and tube structures and cryogenic, radiation-resistant components in the Superconducting Supercollider [7]. This is indeed the problem to convince a traditionally conservative industry in the fact that the superior performance of PCN (which surpass the glas~ transition temperature and hydrophobicity of epoxies while matching their processability and are easily toughened) makes them worth of further investigation in spite of their price, which is currently higher than the price of the epoxies. PCN traditionally should be cured at high temperatures in order to achieve complete conversion, which increases manufacturing cost, but reactive modification of PCN allows decreasing the high temperature of PCN post-curing. However, the primary drawback of PCN which hinders more extensive application of the cured materials is low toughness at room temperature.
