Polymer-disordered carbon black

Imaging and Electrical Resistivity Measurements of Disordered Carbon-Black-Polymer Composites... 

This chapter reviews some of the work done on disordered carbon-black-polymer composites by my collaborators and myself over the past several years. These composites have widespread commercial applications. A qualitative analysis of a transmission electron microscope image is presented. Quantitative analyses of scanning probe microscope images and dc electrical resistivity data are presented. The resistivity and linear expansion of a typical composite between 25 and 180 C are measured and analyzed. The scaling theory of percolation provides a good explanation of most of our data. 

Disordered carbon-black-polymer composites have many common uses in modem technology. These uses include inks, automobile tires, reinforced plastics, wire and cable sheaths, antistatic shielding, resettable fuses, and self-regulating heaters. As an immediate example, the inked letters on this page consist of a disordered carbon-black-polymer composite bound to the surface of the paper. Despite these widespread applications, many of the important physical properties of these composites are not well understood. There is a long history of experimental and theoretical work on disordered carbon-black-polymer composites [7]. One of the most exciting recent advances in the field has been the application of the scaling theory of percolation [2] to these composites. This is based on the many similarities between the percolative transition in a disordered conductor-insulator composite and the thermodynamic phase transition common in many materials. 

Scanning Probe Microscopy. The scanning probe microscope (SPM) is a commercially available instrument (Nanoscope III, from Digital Instruments) that offers a relatively new means to distinguish continuous conductive pathways in disordered carbon-black-polymer composites. Figure 2 is a schematic illustration of how the SPM can be used to image carbon-black-polymer composites. 

The electrical properties of disordered carbon-black-polymer composites are critical to many of their commercial applications. Many research groups have used scaling laws to explain the electrical resistivity of disordered conductor-insulator composites. Some results [P] appear to obey scaling laws with a critical exponent in good agreement with the theoretical three-dimensional percolation value [2] 2.0. Other... 

Before dealing with reinforcement of elastomers we have to introduce the basic molecular features of mbber elasticity. Then, we introduce—step-by-step—additional components into the model which consider the influence of reinforcing disordered solid fillers like carbon black or silica within a rabbery matrix. At this point, we will pay special attention to the incorporation of several additional kinds of complex interactions which then come into play polymer-filler and filler-filler interactions. We demonstrate how a model of reinforced elastomers in its present state allows a thorough description of the large-strain materials behavior of reinforced mbbers in several fields of technical applications. In this way we present a thoroughgoing line from molecular mechanisms to industrial applications of reinforced elastomers. 

Many materials given the name graphite actually have a considerable amount of stacking disorder. For carbons in general, the situation is more complex. Most cokes, petroleum cokes, carbon blacks, carbon fibers, pyrolyzed polymers and mesocarbon microspheres have disordered structures. In such structures the size of the crystallites is small and there is a high probability of random stacking (shifts or rotations) of adjacent carbon layers. This type of disorder is called turbostratic disorder. Hundreds of carbons are commercially available however, selecting the best carbon for use in lithium-ion cells is a subject for much current research. 

Recently, the spectroscopic identification of carbonyl teUuride, obtained by photolysis of H2Te in CO or 1 % CO/Ar matrices at 10 K, was reported. Carbonyl selenide is readily synthesized in situ from R2NC(0)Se R2NH2+ and acids, but little of its chemistry is known. Poly(carbon diselenide) is obtained as a black powder by thermal polymerization or photopolymerization of carbon diselenide. The obtained polymer is highly disordered, and it has a head-to-head polymer structure". 

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