Carbon-filled polymer

Carbon-filled polymers, especially those made from acetylene black, are fair conductors of heat and electricity. Polymers with fair conductivity have... 

Electrodes in a capacitively coupled conductivity detector were made by injection molding carbon-filled polymer into a preformed PS chip. The polymer consisted of three conducting formulations 8% carbon black filled PS, 40% C fiber filled nylon-6,6, and 40% C fiber filled high-impact PS [774]. In another report, a movable contactless conductivity detector was also developed to allow the distance of the electrode to be adjustable [775],... 

Figure 2.2 Single beam PA-FTIR spectra of MTEC carbon-filled polymer...

Nonmetallic conductors and corrosion products. Carbon brick in vessels is strongly cathodic to the common structural alloys. Impervious graphite, especially in heat-exchangers, is cathodic to structural steel. Carbon-filled polymers can act as active cathodes. Some oxides or sulfates are conductors, such as mill scale (magnetite Fe304), iron sulfides on steel, lead sulfate on lead can act as effective cathodes with an important area to that of the anodes. Very frequently, the pores of the conductive film are the preferable anodic sites that leads to localized corrosion (pitting).5... 

Wu, M. and Shaw, L.L., A novel concept of carbon-filled polymer blends for applications in PEM fuel cell bipolar plates, Int. J. Hydrogen Energy, 30, 373, 2005. 

The quantitative aspects of the flow of carbon filled polymer compositions are extremely complex. Not only do the primary structure aggregates possess a complex morphology, but secondary aggregation leads to thixotropic effects, while surface chemical interactions modify the medium. The flow of typical rubber-carbon black mixes is invariably non-Newtonian. 

To retard photodegradation, we also examined the effect of added carbon black (3 wt%) on the weathering of EP and PIB polymer /mirror combinations. Weatherable carbon-filled polymers might be useful on mirror backs. However, the addition of carbon black showed no benefit see Figures 4 and 5,... 

Anodic processes may cause premature failure of oxidisable anode materials, however. A CP system based on a carbon-filled polymer cable anode functioned properly until 6 to 8 y of service. Later, it became increasingly difficult to achieve the criterion of 100 mV depolarisation. Detailed examinations after 15 y showed that the carbon had dissolved from the outer layers of the cable and the polymer had become brittle. This caused high-resistance build-up in the circuit and decreasing current density [40]. In another case using the same anode, however, the material itself was found to be in good condition after 12 y. This was probably related to lower operation current densities. In this case, the system required maintenance in that the power sources, the coimections and the reference electrodes had failed and needed to be replaced [41]. 

Some fillers impart specialist secondary functions to the polymer. Glass in the form of fibres, flakes and hollow microbaUoons or microspheres has been used to fill polymers (Walker and Shashoua, 1996). Metal flakes or powdered metals are used as fillers in electrically conductive plastics, which are used to overcome electromagnetic interference in office equipment. Carbon-filled polymers are good conductors of electricity and heat. 

To obtain the lowest electrical volume resistivities (in the 10 to 10 ohm-cm range) and the lowest contact resistances, polymer resins must be highly Ailed with 70-80% by weight (25-30% by volume) of metal particles and must be thoroughly cured. Silver and silver alloys are the most widely used fillers but, in specific applications, other metal fillers including gold, copper, nickel, and even carbon are used. Carbon-filled polymers are often used to dissipate static electricity or to protect from electromagnetic interference (EMI). 

Carbon-filled polymers are often used to dissipate static electricity or to protect from electromagnetic interference (EMI). 

For carbon nanotubes, discussed in detail in Chapter 10, conductivity is achieved at lower loadings (by weight) but these materials are difficult to disperse in molten polymers. Methods of surface functionalization and lower cost manufacturing must be developed before carbon nanotubes will find wider use as conductive fillers [52, 53]. As an alternative to nanotubes, Fukushima and Drzal [54] have observed conductivity thresholds of less than 3 vol% in composites containing acid-etched or othervdse functionalized exfoliated graphite. These composites retain or improve upon their mechanical properties compared to other carbon-filled polymers. 

K.H. Cheng, Off-line and On-line Ultrasonic Monitoring of Calcium Carbonate Filled Polymers, Brunei University, Uxbridge, UK, 1985. [MSc. Dissertation]. 

Figure 2. Plots of the measured dc current density filled squares, steady state current density open circles, the current density computed from drift mobility measurements and Eq. 1 filled diamonds, the current density computed from the transient dark injection peak values. The contact under test is a carbon filled polymer coated with a transport layer (TPD/polycarbonate) that is known to support trap free hole transport. The insert shows a typical dark injection transient compared to a small signal TOF transient. Conformity of key features of the steady state and transient data with the theory of trap free space charge limited currents provides a self consistent demonstration of contact ohmicity.

A striking enhancement in hole injection efficiency for another type of carbon surface is illustrated in the upper right hand portion of Fig. 6. In this case the substrate contact consists of highly graphitiz carbon particles dispersed in a polymer binder at concentrations exceeding the percolation threshold. Carbon filled polymers are complex percolative systems whose electrical behavior is a function of the filler, the filler interparticle contacts, the host matrix and... 

Figure . J vs. E plots for hole injection into TPD polycarbonate from a carbon filled polymer substrate contact (MystgR ) known to be ohmic for hole injection (filled squares) and an evaporated Au contact (deposited at 10 A/sec) as a function of room temperature annealing time following evaporation on the free surface of a specimen film. Open symbols are the corresponding J vs. E data when positive bias is applied to the substrate and depict the evolution of injection from the evaporated Au top contact in time.

Kataoka, T., Kitano, T., Oyanagi, Y. and Sasahara, M. (1979) Viscous properties of caldiun carbonate filled polymer melts, Rheol Acta, 18,635-9. 

Although Raman spectroscopy is very useful for identification and quantitation of carbonaceous species in various matrices, carbon is the most problematical filler. Common carbon fillers (amorphous coke or graphite) are strong Raman scatterers, but they also strongly absorb the Raman scattered light from the polymer. Thus, a carbon-filled polymer often displays only the spectrum of carbon, or if excessive laser power is used, the sample is burnt by laser absorption. When using 1064 nm excitation (FT-Raman) carbon-filled samples are strongly heated and will incandesce. 

Carbon-Filled Polymer Blends for PEM Fuel Cell Bipolar Plates... 

To address the issues of the manufacturing cost and concurrent reduction in mechanical properties when a high fiUer concentration is used, carbon-filled polymer blends containing a triple-continuous structure in 3D space have been pursued recently [24-26]. Shown in Fig. 12.1 is the schematic of the carbon-filled polymer blend with a triple-continuous structure, consisting of a binary polymer blend (i.e.. Phases A and B) and CB or CNT particles. Both polymer phases are continuous in 3D space. The conductive carbon is preferentially located in Hiase A and its concentration is... 

Fig. 12.2 Samples for (a) conductivity measurements and (b) tensile tests. The direction parallel to the injection flow direction is termed Direction 1, whereas the direction perpendicular to the injection flow direction is called Direction 11 in the text. (From M. Wu and L. Shaw, A novel concept of carbon-filled polymer blends for applications of PEM fuel cell bipolar plates, Int. J. Hydrogen Energ. 2005 30 (4) 373-380, with permission.)...

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