Multiwall carbon nanotubes enhance the fatigue performance of physiologically maintained methyl methacrylate-styrene copolymer

The introduction of multiwall carbon nanotube (MWCNT)-polymer composites ushered in fresh opportunities for engineering new materials with high performance capabilities. The nanoscale dimensions and extraordinary properties of MWCNTs directly address the sub-micron damage mechanisms (such as crazing) that culminate during the fatigue failure of most polymers. The large traditional graphite fibers commonly used in composite materials do little to address these microscopic mechanisms of cyclic deformation; thus, MWCNTs offer new promise for improving the fatigue performance of polymer systems where the previous successes of traditional graphite fibers were limited. To test this theory, small amounts (0-10 wt%) of MWCNTs were added to methyl methacrylate-styrene copolymer (MMA-co-Sty), a chief component of commercial bone cement. The resulting nanocomposites were tested to failure in fully reversed tension-compression fatigue in a 37 degrees C saline environment. Testing at 20 MPa peak stress showed that adding 2 wt% and 5 wt% MWCNTs enhanced the fatigue performance of MMA-co-Sty by 565% and 592%, respectively. These results clearly demonstrate that MWCNTs can substantially enhance the fatigue performance of this polymer. Furthermore, a comparison of these results with the literature shows that MWCNTs are better candidates than traditional graphite fibers for improving the fatigue performance of polymer systems. (c) 2007 Elsevier Ltd. All rights reserved.