CB in Multiphase Blends

It is known that in some polymers, addition of CB to levels above causes a decrease 

Both for reasons of economy and to minimize unwanted effects on mechanical behavior, it is desirable to use the minimum concentration of CB to achieve the required electrical properties. By employing polymer blends, it is possible to create morphologies in which the CB additive concentrates in one phase or, better, in the interphase. There the C B aggregates approach each other closely and the percolation threshold is low. Examples of systems [27-29] where such phase segregation can 

In a noncrystallizable polymer such as atactic polystyrene, is dose to 8wt%. In semicrystalline PE it is 5 wt%, presumably due to segregation of the CB to the noncrystalline phase or the phase boundaries in PE. This segregation is further enhanced in PE/PS blends when the composition allows for continuity of the PE phase and double percolation of the phases and conductive regions [27, 37]. This has been observed at a 45/55 ratio by weight of PE/PS in a melt-blended composition with more than 0.4 wt% (0.2 vol%) carbon black [27]. The effect seems to depend upon the relative interfacial tensions of the polymers and the CB in a manner consistent with the independent observations of Miyasaka et al. [38]. 

---