Contact charging, carbon black

The technology is still not problem-lree. Carbon black is a conductive filler therefore it does not cause an accumulation of static electricity formed because of fi ictional contact with the road. In a silica reinforced tire, static charge is a problem. Remedial actions have already been taken by the introduction of neoalkoxy zirconates and titanates which are capable of dissipating electrostatic charges. The future of the tire is not yet clear but it is expected that silica s share of this market will be 150,000 tons. This will be supplied to make full silica and silica/carbon black tires. 

Contact electrification of insulative materials, predominantly in film form, has been studied in many laboratories. In this paper, electric field dependent charging of polymeric and polymer-carbon black powders in contact with a metallic electrode has been studied. Results show the charging behavior to be strongly dependent on the composition of the powder surface. Carbon black loading, type of carbon black and degree of dispersion are methods used to alter the powder surface. The field dependent contribution to the charge exchange dominates over the zero field values. 

The changes in contact charging observed with different carbon blacks at the surface of styrene copolymer particles is shown in Figure 8. These samples all have 5% of a carbon black tacked onto the... 

It is worth noting that the model for the carbon black surface deduced from these observations possesses a limited predictive capability for other materials systems than those studied herein. The current viewpoint that polymer interactions may be discussed in terms of Lewis acidity and basicity associated with particular molecular groups comprising the polymer(44-46) coincides with the present description of the origin of carbon black activity. Specifically BPL, which contains localized Lewis acid sites, can be expected to interact readily with polymer sites that are capable of acting as a Lewis base towards the carbon sites. On the other hand Graphon, which lacks these localized Lewis acid sites, is predicted to interact weakly with the same polymer sites. Contact charge injection experiments (3 3) provide a particularly sensitive probe of the carbon-polymer interaction and may supply the best means to test such model predictions. 

Electrical Conductivity. This quality is important to bleed off static charge and to avoid electromagnetic interference (EMI) (Sec. 5.9). It can be produced by adding carbon black, graphite, and especially metallic fillers (Table 5.23). This requires particle-to-particle contact, so flakes are more efficient than simple powders, and fibers are most efficient of all (Table 5.24). 

Principles and Characteristics The vibrating capacitor or Kelvin method [362, 363] is a well-established experimental technique for measuring the contact potential difference (CPD) or work function for a variety of materials, including polymers [364] and carbon-black [365]. Here, the sensitivity of the CPD to the appearance of electronic surface states and surface charges is used. Scanning Kelvin microscopy (SKM) allows for mapping of the two-dimensional CPD distribution on sample areas of 1 cm with /u.m resolution without extensive experimental requirements [366]. 

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