The Research Of Dielectric Properties On Cyanate Ester Composites

In the last decades, cyanate ester resin has become established as one of the most important high performance thermosetting resins and its polymeric composites have attracted more and more attentions for their advantages in mechanical properties, lightweight and easy processing. The unique chemical characteristic of cyanate ester monomer endow them excellent properties, such as good mechanical properties, high thermal properties, outstanding dielectric properties and low moisture absorption and so on. They have been widely used in aerospace structures, dielectrics, adhesives and encapsulants in recently years.Cyanate resin is a family of organic compounds which have two or even more cyanate groups. Its general formula is N=C-0. Ar-O-ON. It was developed since1980s, with sound comprehensive properties. CE has comparative lower Dielectric Constant (ε=2.8-3.2), lower Dielectric loss (tan δ=2.0×10-3～8.0×10-3), lower moisture absorption<1.5%) and higher decompose temperature(>350℃). The CE can be dissolved in general organic solvent and has good infiltration properties, adhesive properties, coating properties with reinforcement such as carbon fiber, glass fiber and PA fiber. It can be adapted into several technical methods.Bisphenol A-cyanate ester (BACy) is a unique type of cyanate ester that is under investigation for use as the matrix material for adhesives with enhanced ambient temperature processability. BACy monomer has a low viscosity at room temperature and excellent storage characteristics and the cured polymer has a high glass transition temperature and excellent mechanical properties. The disadvantage of the BACy is its electric property.In this dissertation, bisphenol A cyanate ester resin with carbon nano-tubes and nano-SiO2composites has been prepared. Their electrochemistry, mechanical, dielectric, thermal properties were all studied. The properties of composites which composed by bisphenol A cyanate ester resin with1%-2%carbon nano-tube and1%-5%nano-SiO2were also studied; the reaction principles of the modification resin system were also mentioned in a primary level and technical were all studied. The results shows that:The composites of bisphenol A cyanate ester with1%-5%nano-SiO2dielectric constant and dielectric loss remain in a lower range between (ε=2.88～2.95) and between (tan5=3.72×10-3-3.38×10-3); the modified resin composites (1%-2%carbon nano-tube) has nice thermal properties that its thermal decomposition temperature is above360℃and has conductivity (It was around5×10-7S/cm). To additional, cyanate ester of novolac was synthesized. The cyanate ester of novolac, has lower content of impurity, higher char yield (when novolac is5%, char yield is over34.4%)and good processability, which is suitable for use as the matrix of high performance ablative material.