Phenomena of Conductivity in Carbon Black-Filled Polymers

Cabot Corp., Colloids Ltd. (UK), Hubron Manufacturing Div., Ltd. (UK), Polychem USA, A. Schulman, Singapore Polymer Corp. (PTE.) Ltd, and others. 

Carbon black is reported to have occupational exposure limits (OEL) of 3.5 mg/m according to the American Conference of Governmental Industrial Hygienists (ACGIH) regarding threshold limit value (TLV) National Institute for Occupational Safety and Health (NIOSH) regarding recommended exposure limits (REL) and the Occupational Safety and Health Administration (OS HA) regarding permissible exposure limits (PEL). A detailed discussion of CB safety, health, and environmental considerations can be found on the veb site of the Cabot Corporation [11]. 

In general, the quenching step of manufacture presents an opportunity for oxidation of the fine CB po vder. Surface groups can be further enhanced intentionally by oxidation vith acid or ozone. Surface groups formed in this vay are primarily carboxylates and phenolics. An untreated black typically has pH 6 and volatile content of 0.5-1.5%. Oxidized blacks have pH 6 and volatile content of 3-10%. 

Phenomena of Conductivity in Carbon Black-Filled Polymers 

When the concentration of CB in a polymer is progressively increased, there is a critical volume fraction, Vc, at vhich the electrical conductivity increases by several 

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