Electrically Conductive Compositions

Injection-moldable electrically conductive composition based on FCP are useful in a wide variety of applications, including  

Electrically conductive compositions are fabricated by blending an injection-moldable LCP and nickel-coated graphite fibers that are impregnated with a non-liquid-crystalline thermoplastic binder resin. The blending is done below the melting point of the LCP. The mixture is processed in an injection molding machine. A balance among conductivity, process-ability, and structural properties is desirable. Materials for electrically conductive compositions are summarized in Table 16.6. 

Suppliers and commercial grades are shown in Table 16.7. Monomers and structural units used in commercial available LCPs have been sununarized in the literature. Vectra types are random copoly(ester)s based on HBA and 2-hydroxy-6-naphthoic acid or copoly(ester amide)s based on 4-aminophenol and TPA. Xydar types are fully aromatic poly(ester)s based on HBA, BP, and TPA. Neat poly(ethylene terephthalate), is not a LCP. However, by the introduction of HBA it becomes a LCP. The ethylene groups act as flexible spacers that reduce the nematic transition temperature. Commercial available types of this kind are X7G and Rodrun types. Tradenames appearing in the references are shown in Table 16.8. 

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A number of processes have been used to produce carbon black including the oil-furnace, impingement (channel), lampblack, and the thermal decomposition of natural gas and acetjiene (3). These processes produce different grades of carbon and are referred to by the process by which they are made, eg, oil-furnace black, lampblack, thermal black, acetylene black, and channel-type impingement black. A small amount of by-product carbon from the manufacture of synthesis gas from Hquid hydrocarbons has found appHcations in electrically conductive compositions. The different grades from the various processes have certain unique characteristics, but it is now possible to produce reasonable approximations of most of these grades by the od-fumace process. Since over 95% of the total output of carbon black is produced by the od-fumace process, this article emphasizes this process. 

Sichel, E. K. Gittleman, G. I. Sheng, P. in "Carbon-Black-Polymer Composites. The Physics of Electrically Conducting Composites", Sichel, E. K., Ed., Dekker, 1982, p 51-77. 

Electrically conducting composite comprising a non-conducting polymer matrix and an electrically conducting material. 

While carbon fiber (thickness on the order of 1000 nm) composites offer very strong materials, carbon nanotubes make even stronger composites. These carbon nanotubes have aspect ratios of over 1000 (ratio of length to diameter). Further, because some carbon nanotubes are electrically conductive, composites containing them can be made to be conductive. A number of carbon nanotube matrixes have been made including using a number of engineering resins, such as polyesters, nylons, polycarbonates, and PPE. 

Examples of conductive ABS polymer composites include electromagnetic shielding materials (56,57) and electrically conductive composite plastic sheets, which may be used for packaging of integrated circuit devices (58,59). 

Carbon Black-Polymer Composites The Physics of Electrically Conducting Composites, edited by Enid Kell Sichel... 

Saraf RF, Roldan JM, Gaynes MA, Booth RB, Ostrander SP, Cooper El, Sambucetti CJ. Electrically conductive compositions. Eur Pat Appl EP 805616 A1 9711105 11 pp... 

Ferrocene doping provides an electrochemical probe of the material during gelation, reporting in particular on the mobility of the probe as measured by the diffusion coefficient.133,134 If necessary the sol-gel material can be loaded with carbon powder to confer electrical conductivity (composite ceramic carbon electrodes, CCEs).135 Single-walled nanotubes in vanadia aerogels exhibit high capacities for lithium intercalation.136... 

H. Kawamoto, Carbon Black-Polymer Composites, The physics of electrically conducting composites, Dekker, New York, (1982), p.135. 

A novel method for achieving electrically conductive composites was noted by Gubbels et al. 

The electrically conductive composites prepared by these methods are not sufficiently conductive for shielding of electromagnetic interference. Still more effective in producing conductive aramids is electroless plating. A high electrically conductive fiber is obtained. The fiber is impregnated with metal complexes using supercritical carbon dioxide. 

In situ polymerization to prepare immiscible blends was pioneered by Watkins and McCarthy [108], stimulating other researchers to apply this methodology to prepare novel polymer blends [109-112], fiber-reinforced composite materials[39], and electrically conducting composites [66, 67, 113-116]. Polymer blends produced in this manner include polystyrene/poly(vinyl chloride) [117, 118], polysty-rene/PET [119], nanometer-dispersed polypropylene/polystyrene interpenetrating networks [120], polypropylene/polystyrene [121] and polyethylene/polystyrene [122]. The resultant polymer blend may have a unique morphology compared to the traditionally prepared counterpart (if it is feasible to prepare such a blend via conventional procedures) and therefore demands a thorough investigation. 

Example 5.20b Preparation of Electrically Conductive Composites by Filling Poiycarbonate (PC) with Carbon Black (CB)... 

Miyata, S., and T. Ozio. 1987. Process for producing electrically conductive composite polymer article. US Patent 4,699,804. 

Newman, P.R., L.R. Warren, and E.R Witucki. 1986. Process for producing electrically conductive composites and composites produced therein. US Patent 4,617,228. 

More recently nanoscale fillers such as clay platelets, silica, nano-calcium carbonate, titanium dioxide, and carbon nanotube nanoparticles have been used extensively to achieve reinforcement, improve barrier properties, flame retardancy and thermal stability, as well as synthesize electrically conductive composites. In contrast to micron-size fillers, the desired effects can be usually achieved through addihon of very small amounts (a few weight percent) of nanofillers [4]. For example, it has been reported that the addition of 5 wt% of nanoclays to a thermoplastic matrix provides the same degree of reinforcement as 20 wt% of talc [5]. The dispersion and/or exfoliahon of nanofillers have been identified as a critical factor in order to reach optimum performance. Techniques such as filler modification and matrix functionalization have been employed to facilitate the breakup of filler agglomerates and to improve their interactions with the polymeric matrix. 

P(l) If aluminium honeycomb is used with electrically conducting composites (e.g. carbon fibre composites), construction shall ensure that the honeycomb is electrically insulated from the core by using a glass fibre interlayer to prevent potential internal galvanic corrosion problems occurring in wet environments. 

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