Enhancement of dynamic mechanical properties and flame resistance of nanocomposites based on epoxy and nanosilica modified with KR-12 coupling agent

The epoxy/silica nanocomposites containing a wide range of isopropyltri[di(octyl) phosphate] titanate coupling agent (KR-12) modified nanosilica (m-nanosilica) loading (0–7 wt%) cured with tetrabutyl titanate hardener were prepared. Their morphology, thermal stability, thermal expansion, and mechanical properties including hardness, abrasion resistance were investigated. The wetting ability of epoxy-nanosilica systems on glass surface was assessed based on static contact angle. The obtained results showed that the contact angle of the nanocomposites containing m-nanosilica is slightly changed as compared to the contact angle of pure epoxy resin and lower than that of the nanocomposite containing unmodified nanosilica. The data of dynamic mechanical analysis of the nanocomposites using different nanosilica content indicated that the presence of m-nanosilica lowered the recovery energy of the nanocomposites to 41.62% as compared to neat epoxy. The limiting oxygen index (LOI) of the nanocomposites confirmed that the m-nanosilica increased the flame retardance of epoxy matrix. When using 7 wt% of m-nanosilca, the LOI value of the nanocomposite was 27.4 while this index of neat epoxy was 21.6. The scanning electron microscopic images of residual char combustion of the nanocompsites indicated a formation of nanosilica layer contributed to restrain combustion of the material.