Thermomechanical properties of graphite nanofibers/poly(methyl methacrylate) composites

Aligned chemical vapor deposition (CVD)-grown graphite nanofibers (GNFs) were used as a conductive filler in a poly(methyl methacrylate) (PMMA) system to investigate the effect of GNF content on the thermo-mechanical properties of GNFs/PMMA composites. In the result, an electrical percolation threshold for the composites was formed between 1 and 2 wt% GNF contents, which depended on high aspect ratio and good electrical conductivity of GNFs enabling them to percolate systems at low volume fraction. All of the composites contained individually dispersed GNFs after initial shear-intensive stirring. Negative surface charges on the GNFs led to charge-stabilized dispersions. Above the melting temperature of PMMA, the GNFs re-aggregated on application of elevated temperatures and/or modest shear forces. Additionally, the composites exhibited higher thermal and impact properties and lower thermal shrinkage compared with those of the neat PMMA. Consequently, it was demonstrated that GNFs had positive impacts on the thermo-mechanical properties of polymer composites and that they had the potential to be effectively utilized to enhance the structural performance of composites. (C) 2009 Elsevier B.V. All rights reserved.