MWNTs were first used as electrically conductive
fillers in plastics, taking advantage of their
high aspect ratio to form a percolation network
at concentrations as low as 0.01 weight percent
(wt %). Disordered MWNT-polymer composites
reach conductivities as high as 10,000 S m–1 at
10 wt % loading (34). In the automotive industry,
conductive CNT plastics have enabled
electrostatic-assisted painting of mirror housings,
as well as fuel lines and filters that dissipate electrostatic
charge. Other products include electromagnetic
interference (EMI)–shielding packages
and wafer carriers for the microelectronics industry.
For load-bearing applications, CNT powders
mixed with polymers or precursor resins can increase
stiffness, strength, and toughness (35). Adding
~1 wt % MWNT to epoxy resin enhances
stiffness and fracture toughness by 6 and 23%, respectively,
without compromising other mechanical
properties (36). These enhancements depend
on CNT diameter, aspect ratio, alignment, dispersion,
and interfacial interaction with the matrix.