Phenyltrimethoxysilane treated silica (SiO2) nanoparticles filled high performance poly(etheretherketone) matrix nanocomposites were prepared using hot pressing. The experimental density of the nanocomposites containing 3vol.% SiO2 was very close to the theoretical density, while thereafter it decreased compared to theoretical density. Scanning electron microscopy showed uniform dispersion of SiO2 in the matrix. The addition of treated SiO2 did not change the crystal structure of the matrix. The coefficient of thermal expansion (CTE) of the nanocomposites decreased approximately 25% at 20vol.% SiO2 content. The values of CTE of the nanocomposites were lower than the values predicted from the rule of mixtures indicating good adhesion between the SiO2 and the matrix. The presence of SiO2 in the matrix did not affect significantly the melting point and the glass transition temperature of the matrix. The nanocomposites showed thermal stability better than 560°C. The dielectric constant and dissipation factor were reduced slightly for the nanocomposites compared to those of pure PEEK and untreated nanocomposites. The improvement in dimensional stability, dielectric properties and the better thermal stability of the nanocomposites make them promising candidates for the printed circuit boards or electronic substrates.
