a) b - École Polytechnique de Montréal

2.3.1.1 Conducting Polymer Composite Materials (CPCM)
The development of efficient conductive polymer composites materials(CPCMs) remains an
important endeavor in light of growing energy concerns. Conductive and anti-static compounds
have been commercially prepared for more than 80 years. A CPCM consists of a random
distribution of conducting filler throughout an insulating polymer; this is of interest for several
application fields. It is crucial to choose a suitable filler-polymer pair in the production of
CPCM. A good balance between filler-polymer and filler-filler interactions can lead to the
formation of a continuous network, but filler particles tend to stick together if the filler-filler
interactions dominate and aggregates rather than forming network of particle-contacting chains.
On the other hand, a good adhesion between polymer and filler results in an insulating layer
around the filler particles and prevents formation of current-conducting chains. Many conductive
polymer composites exhibit percolation characteristics(Chung, Sabo, & Pica, 1982; Flandin,
Bréchet, & Cavaillé, 2001).
The most universal conducting filler for this purpose is carbon black, because dispersion of
conducting carbon black particles in synthetic polymers is a very efficient way of providing them
with semi-conductive and antistatic properties. From the economical and technical viewpoint,
decreasing the carbon black percolation threshold as much as possible in the blend is desirable.
Consequently, the percolation theory is the most adequate for modelling conductivity of CPCM.
It has been observed that insulator-conductor transition in polymer-filler composites depend on
the aggregation(Masao Sumita, Kayaki, & Miyasaka, 1986), size, size distribution, structure and
porosity of the conducting particles(Verhelst, Wolthuis, Voet, Ehrburger, & Donnet, 1977), on
rheological properties of polymer components(Miyasaka et al., 1982b), and on processing
conditions.
The curve of conductivity versus filler concentration is S-shaped (Figure 2-18), which clearly
demonstrates a relatively narrow filler loading range during which a small increase in loading
will result in a drastic increase in conductivity. This change implies some sudden changes in the
dispersing state of conductive particles at a critical point (percolation threshold), i.e. the
coagulation of particles to form networks which facilitates the electrical conduction through the
composites. Figure 2-18 shows the conductivity of a thermoset system of multiwall-nanotube/
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