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a) b - École Polytechnique de Montréal

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Now, as the conductivity of HDPE, air, and PSS polyelectrolytes are very low, it is assumed that<br />

the entire sample, except the PANI network, is void. This implies that the HDPE substrate and<br />

PSS network are consi<strong>de</strong>red as porous parts in or<strong>de</strong>r to propose a mo<strong>de</strong>l to predict the<br />

conductivity of the PANI network. Thus, porosity of the sample, including HDPE, voids, and the<br />

PSS network can be calculated as follows:<br />

Equation A-2.3 Vvoid<br />

( 3.<br />

5 − 0.<br />

0076)<br />

Θ =<br />

V<br />

total<br />

=<br />

3.<br />

5<br />

Therefore, a total porosity of 99.78% for this sample is observed.<br />

=<br />

0.<br />

9978<br />

The ol<strong>de</strong>st and most well-known theory of low porosity levels was <strong>de</strong>vised by Maxwell and<br />

predicts the conductivity of CPPD as follows:<br />

Equation A-2.4<br />

⎛ 2 − 2Θ<br />

⎞<br />

σ = σ 0⎜<br />

⎟ = 0.<br />

00147σ<br />

0<br />

⎝ 2 + Θ ⎠<br />

where σ is the conductivity of the porous material, σ0 is the conductivity of the pure material, and<br />

Θ is value of porosity. The porosity of a porous system ranges from 0 to 1. Fricke (Fricke, 1924)<br />

in 1924 ad<strong>de</strong>d a shape factor due to the geometry of pores in the expression:<br />

Equation A-2.5<br />

⎛ 1−<br />

Θ ⎞ ⎛ 0.<br />

0022 ⎞<br />

σ = σ 0⎜<br />

⎟ = ⎜<br />

⎟σ<br />

0<br />

⎝1<br />

− ( 1−<br />

f ) Θ ⎠ ⎝ 0.<br />

0022+<br />

0.<br />

9978f<br />

⎠<br />

f varies from 1.5 for spherical pores to infinity for thin, disc-shaped pores. Koh (Koh & Fortini,<br />

1973) <strong>de</strong>veloped the following equation for highly porous materials with porosity ranging from<br />

0.38 to 0.9:<br />

Equation A-2.6 ⎛ 1 − Θ ⎞<br />

σ = σ 0 ⎜<br />

= 0.<br />

0002 σ<br />

2 ⎟<br />

0<br />

⎝ 1 + 10 Θ ⎠<br />

Skorokhod (Skorokhov, 1972) found that for porous bodies with wi<strong>de</strong> porosity, the equation<br />

would become:<br />

248

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