| Composite materials are heterogeneous systems where a filler is used to reinforce a matrix. In recent years, the use of nano-scale fillers has become increasingly popular for composite systems. Carbon nanotubes have been used as nano-fillers because they are extremely stiff and strong, and conduct electricity and heat, but are very expensive. Exfoliated graphite has the same mechanical properties as carbon nanotubes, but has platelet morphology. It is much less expensive than carbon nanotubes ({dollar}5/lb. compared to {dollar}50–500/g). The interfacial area of exfoliated graphite is very high, and the interfacial adhesion is critical to the success of its implementation as a nano-filler. The surface energy of exfoliated graphite has not been extensively studied. It is the focus of this work to characterize the surface chemistry of exfoliated graphite, modify it by various techniques and study its effect on the physical properties of exfoliated graphite nanocomposites. X-ray photoelectron spectroscopy and a surface energy study utilizing capillary wicking (a procedure for which was developed specifically for this study) were used to characterize the surface. Plasma treatments and polymer grafting were used to modify the surface. Flexural testing was used to determine mechanical properties and scanning electron microscopy was used to study the dispersion morphology on fracture surfaces. Extrusion mixing improved the mechanical properties, but chemical modification did not improve these properties. |
