What is the Carbon black (CB) ?

Carbon black was chosen as one of the components of the hybrid system. It is electrically conducting and widely used in polymer matrix composites for different applications [17]. It exists in the form of aciniform aggregates (the smallest dispersible unit) formed of spheroidal particles of elemental carbon [17], [18]. The size of the particles varies between 15 and 75 nm whereas for the aggregates it varies from 50 to 400 nm. Furthermore aggregates tend to collapse in agglomerates with a size between 100 and 1000 nm [19]. Figure 4 shows agglomerates of the carbon black used in this work. The particles' microstructure however is not well understood. Paracrystalline domains where planes of graphite lay in a turbostratic* stacking have been found [20]. For the graphitic structures, graphite plates with an interplane distance deviating from the expected have been observed by X-Ray diffraction [17]. In the center of the particles a lack of order in the structure is suspected [17].

Carbon black is obtained from the partial combustion or thermal decomposition of hydrocarbons [21] usually through the furnace process (from petrochemical or carbochemical origin) or the acetylene process (from acetylene gas) [17].

The conductivity of carbon black varies between 10-1 and 102 (ohm.cm)-1. Carbon black grades with high specific volumes, high structures and absence of impurities or chemical groups are preferred for conducting filled polymers. In addition, because porosity in carbon black increases the specific volume, higher porosity affects positively the conductivity of the material. High structured carbon, i.e. with larger number of particles per aggregates and branched sides, gives higher conductivity when added to a polymer although the specific volume is decreased [17]. This apparent contradiction is attributed to small particles, as in the case of high structured carbon blacks, that tend to aggregate and form agglomerates which can enhance the electrical properties


Among the main drawbacks of carbon black, health concerns must be considered with caution [21]. The International Agency for Research on Cancer (IARC) has classified it in the Group 2B, carcinogens. Other drawbacks, especially when added in large amounts to a polymer matrix, are the increase of viscosity and the detrimental effect on mechanical properties such as flexibility [18].



source : Elena Álvarez Díez