Cyanate Ester/ TriSilanolPhenyl-POSS Nanocomposites

Kaiwen Liang, Hossein Toghiani, and Charles U. Pittman Jr. Dave C. Swalm School of Chemical Engineering, Mississippi State University, MS 39762. Department of Chemistry, Mississippi State University, MS 39762. Carbon-carbon materials are traditionally designed for high temperature applications. Carbon-carbon materials are composites formed by impregnating continuous carbon fiber cloths or preforms with an organic thermoset resin (usually a phenolic resin) and curing the resin. High temperature pyrolysis is then employed to carbonize the matrix resin. Outgassing during pyrolysis creates porous carbon, which is reimpregnated with additional resin and then repyrolyzed. This process is repeated to densify the structure. Under inert atmospheric conditions, carbon-carbon composites have very high use temperatures. However, they exhibit thermo-oxidative instability at ~ 400 C without oxidation protection [1]. Cyanate esters are also good candidates for carbon-carbon composites. The term “cyanate ester resin” is used to describe both prepolymers and final cured resins, based on the cyanate ester functionality. The prepolymer contains reactive ring-forming cyanate (-O-C≡N) functional groups [2-3]. Cyanate ester monomers and their oligomers are – OCN-functionalized bisphenols. During curing, these monomers cyclotrimerize to substituted triazine rings by heating. Figure 1 shows the cure reaction for a bisphenolderived cyanate ester used in this work (PT-15 from Lonza). This reaction can be catalyzed by metal ions or phenolic hydroxyls, or it can simply be thermally polymerized at temperatures of 140 oC or higher. Cyanate esters are being studied in our group as