Synthesis and Characterization of Carbon Spheres/Poly(Methyl Methacrylate) Composites with Enhanced Electrical Conductivity and Vickers Microhardness

Carbon spheres used as filler materials are ideal and promising nanostructures to obtain composites with enhanced electrical and mechanical properties. Solid carbon spheres synthesized previously in this research by chemical vapor deposition were incorporated in poly(methyl methacrylate) through solution mixing at different loads (5 wt.%, 7 wt.% and 9 wt.%). Scanning electron microscopy showed a uniform carbon sphere dispersion into the polymer matrices. The characteristic peaks of carbon spheres, D-band at 1321 cm−1 and G-band at 1593 cm−1, were observed in Raman spectroscopy. Fourier transform infrared spectroscopy determined the main functional groups of composites corresponding to C–H, C–O, C=O, CH2 and CH3 stretching. The composites were evaluated by the Vickers Microhardness (HV), the Van der Pauw and the two-point methods. The hardness and electrical conductivity were enhanced according to the carbon sphere loading increase. The maximum carbon sphere load (9 wt.%) in composites showed an important microhardness improvement (147%). Electrical conductivity values significantly increased until 1.66 × 10−3 S/cm (10 orders of magnitude of improvement) at 9 wt.% of carbon sphere composites.