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a) b - École Polytechnique de Montréal

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Omonov et al. found double percolated structures for ternary 40PA6/30PP/30PS (Figure 2-8a)<br />

and 40PA6/(25/5)(PP/PP–MA2)/(25/5)(PS/SMA2) (Figure 2-8b) blends. In this work, the<br />

observed results were opposite to the prediction of spreading theory, which is partial wetting.<br />

They found that <strong>de</strong>spite the negative values of spreading coefficients, a complete wetting case<br />

with PA6 phase at the interface is observed. The gravimetric measurements for all phases<br />

showed that for 40PA6/30PP/30PS, all phases have more than 97% continuity while PA6<br />

separates the PP and PS phases. Figure 2-8b shows that addition of a compatibilizing agent to the<br />

sample does not change the location of phases. It only reduces phase sizes, but PA6 still remains<br />

at the interface of the two other phases.<br />

a) b)<br />

Figure 2-8. Scanning electron micrograph of a) 40PA6/30PP/30PS; formic acid extracted<br />

surfaces, and b) 40PA6/(25/5)(PP/PP–MA2)/(25/5)(PS/SMA2); formic acid extracted surfaces<br />

(Harrats, et al., 2005)<br />

One of the most important applications of double-percolated structures is the preparation of<br />

conductive polymer blends. Since locating the conductive phase at the interface <strong>de</strong>creases the<br />

percolation threshold of continuity of the middle phase, it is predicted that the percolation<br />

threshold of conductivity of the blend is reduced significantly. Narkis et al.(Narkis et al., 2000b;<br />

Zilberman, Siegmann, & Narkis, 1998, 2000a, 2000b) studied various polymer blends consisting<br />

of two immiscible thermoplastic polymers and PANI and tried to locate PANI at the interface of<br />

two other polymers, but they were not successful. They showed that for CoPA/LLDPE/PANI<br />

(Figure 2-9) and (PS/DOP)/LLDPE/PANI (Figure 2-10), changing the concentration of the<br />

31

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