Method for Modifying Mechanical Properties of Carbon Nano-fiber Polymeric Composites

Composites consisting of different quantities of vapor grown carbon nano-fibers (untreated and oxygen plasma treated) in a polypropylene matrix have been prepared using extrusion and injection molding technique. In order to increase the adhesion between fibers and polymer matrix, oxygen plasma treatment onto the carbon nano-fiber surface is applied. The graphitization degree, the electrical resistivity, the water contact angle, the surface energy, the morphology, and the structure of the carbon nano-fibers are characterized. The fiber—matrix interface and the fiber orientation and distribution in the composite are determined by scanning electron microscopy. Measurements of the mechanical properties show that the composites containing 5 wt% oxygen plasma treated fibers have a better tensile strength compared with composites containing 5 wt. % even 10 wt. % untreated fibers.