Studies on novel cyanate esters gel blends and composites

Abstract

Cyanate ester resins have recently attracted increasing attention as next-generation thermosetting polymer matrices because of their high thermal stability, excellent mechanical properties flame resistance, low outgassing, and radiation resistance. Applications of cyanate ester include structural aerospace, electronic, microwave-transparent composites, encapsulates, and adhesives. The aim of the present research work is to synthesize novel cyanate esters with different linking backbones that are expected to achieve good thermal and mechanical properties. In order to achieve the goal of the research, different types of cyanate ester monomers with keto-ene group, aliphatic group with different chain length, azomethine, azo, imide, and azomethine and imide oligomers have been prepared. A study of the cure behavior of epoxy, BADCy, epoxy-cyanate ester/BADCy-cyanate ester blends and epoxy-cyanate ester-MWCNT/BADCy-cyanate ester-MWCNT formulations by DSC reveals that the peak curing temperature of the epoxy / cyanate ester blends are higher compared to neat epoxy; in BADCy /cyanate ester blends peak curing temperature is shifted to a lower value compared to neat BADCy; on addition of MWCNT in epoxy-cyanate and BADCy-cyanate ester the peak cure temperature decreases with increase in MWCNT content. The SEM image of BADCy-VCy2 blend reveals a smooth homogeneous morphology, indicating complete miscibility between the two components; while that of BADCy-VIICy2-MWCNT nanocomposite reveals a rough morphology. The epoxy-cyanate ester blends have better moisture resistance compared to neat epoxy system and BADCy-cyanate ester blends have lower moisture resistance compared to neat BADCy due to aliphatic ester, imide, azo and azomethine groups, which have good affinity for water. The I and II series cyanate ester have the best thermal stability and comparable mechanical properties. Incorporation of POSS-Cy enhances the thermal stability and mechanical properties of neat epoxy resin. newline newline newline