Processing and characterization of nanographene platelets modified phenolic resin as a precursor to carbon/carbon composites (part II)

Nanocomposites were formed by curing the dispersion of carbon nanofillers—nanographene platelets and vapor grown carbon nanofibers—in resole type phenolic resin. X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, thermal expansion, and thermogravimetric and flexure testing were carried out to study the morphology and thermal and mechanical properties of the manufactured nanocomposites. The coefficient of thermal expansion decreased by 15.36% (73.83 µm/m℃) and 14.23% (74.81 µm/m℃) with 1.5 wt% nanographene platelets and 1.5 wt% vapor grown carbon nanofibers, respectively, compared with neat phenolic (87.23 µm/m℃) in the temperature range 60–80°. The flexure strength of neat phenolic resin increased by 31.62% (48.57 MPa) and flexure modulus by 42.23% (2.9 GPa) at 0.5 wt% nanographene platelets. Comparatively, vapor grown carbon nanofibers at 1.5 wt% increased the flexure strength by 14.3% and flexure modulus by 23.5%. Nanographene platelets and vapor grown carbon nanofibers increased the char content of neat phenolic resin. The char content increased by 200% at 800℃ in 5 wt% nanographene platelet nanocomposites, compared with 75% increase in 3 wt% vapor grown carbon nanofibers nanocomposite. Nanographene platelets were more effective than vapor grown carbon nanofibers in lowering the coefficient of thermal expansion of neat phenolic, in improving its flexure strength and modulus and in increasing the char yield. The results indicate that nanographene platelets can be effectively used as carbon nanofiller in the manufacture of carbon/carbon composites.