Conductive thermoplastic compounds properties

Carbon-black-filled rubber compounds are usually produced on Banbury-type mixers, while conductive thermoplastics are preferably produced on twin-screw extruders. Unlike other filled compounds or polymer blends it is essential to adhere very precisely to the carbon-black concentration and the production parameters, since a very delicate balancing act is usually required to stay on the tight-rope of optimum composition and avoid falling into the pits of insufficient conductivity, inadequate mechanical properties or sharply increased viscosity. 

Poly(phenylene oxide) (PPO) is a thermoplastic, linear, noncrystalline polyether commercially produced by the oxidative polymerization of 2,6-dimethylphenol in the presence of a copper-amine catalyst. PPO has become one of the most important engineering plastics widely used for a broad range of applications due to its unique combination of mechanical properties, low moisture absorption, excellent electrical insulation property, dimension stability and inherent flame resistance. This chapter describes the recent development of this polymer, particularly on the production, application, compounding, properties of its alloys and their general process conditions. The polymerization mechanism and thermal degradation pathways are reviewed and new potential applications driven by the increasing environmental concerns in battery industry, gas permeability and proton-conducting membranes are discussed. 

The properties of some thermoplastic compounds that were prepared with Eeonomer additives are given in Table I. Also, listed as a control for comparison is a nylon-6 compound with uncoated carbon black. The mechanical properties of the Eeonomer - nylon compounds are observed to be similar or better than the control. Note that in the nylon-6 case, the polypyrrole - Eeonomer compound offers improved mechanical properties over the polyaniline composite while still retaining the same conductivity level. 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

Carbon black can fnnction as a UV stabilizer, thermal antioxidant, extender in crosslinked polyethylene (XLPE) cable compounds, antistat in vinyl records, modifier of polymerization rate in nnsaturated polyesters, conductive filler, and colorant. Although commonly used in rubbers and thermoplastics, carbon black does not improve the properties of thermosetting resins significantly. However, it is often used as a pigment and for obtaining electrical conductivity. 

Carbon black filled antistatic and conducting composites usually contain 10-30 wt.% filler. (Addition of 1-2 wt.% carbon black for improving the weatherability essentially does not change the conductivity, although it somewhat increases the dielectric loss). The addition of conducting carbon black to thermoplastics increases not only the electrical conductivity, but also the modulus, tensile strength, hardness, melt viscosity and the heat distortion temperature of the compound. It reduces, however, the elongation to break and impact properties. 

They are required for thermoplastics applications where surface electric charge must be controlled or prevented. There are a number of compounds available for this function and these can be divided into two general categories bulk and surface-modifying. Bulk additives may be simple, such as carbon black, which, when added in sufficient concentration, provides a semiconducting matrix, thus controlling the accumulation of localized charge. Metal salts can also be used for this purpose in some polymers. Cationic compounds can impart bulk conductive properties and these include compounds with a bulky cation such as quaternary ammonium, sulphonium salts, or imidazoline compounds. Anionic compounds are also used and these include, for example. 

One of the main limitations of intrinsically conductive polymers (ICP s) towards their wide application as conductive additives for thermoplastics is their poor thermal-oxidative stability at typical melt processing temperatures (i.e., above 200 °C). On the other hand, the use of high surface area carbon blacks (CB) as conductive additives is limited due to the increased melt viscosity of their blends with thermoplastics. Eeonomers are a new class of thermally stable, chemically neutral, and electrically conductive composites made via in-situ deposition of conductive polyaniline (PANI) or polypyrrole (PPY) on CB substrates. Eeonomer composites are more stable (up to 300 °C) than pure ICP s and more easily processible with thermoplastics than CB. Use of Eeonomers as conductive additives for plastics lead to compounds with improved electrical, mechanical, and processing properties. By varying Ae conductive polymer to CB ratio, it is possible to fine tune the polarity of Eeonomer composites and achieve very low percolation thresholds. This control is possible because of preferred Monomer localization at the 2D phase boundary of the immiscible polymer blends. 

Eeonomers are a new class of conductive additives for thermoplastics made via in-situ deposition of intrinsically conductive polyaniline or polypyrrole on carbon black. Eeonomers are highly thermally stable, pH neutral conductive materials that are compatible with the chemistry and melt processing conditions of acid sensitive polymers. Compounding studies with thermoplastics indicate better electrical, mechanical, and melt flow properties of Eeonomer blends as compared to blends with traditional carbon blacks. In co-continuous plastic blends it was possible to fine tune the polarity of Eeonomer by varying the conductive polymer to CB ratio. The same variation affords very low percolation thresholds due to preferred Eeonomer localization at the 2D phase boundary. 

One of the most striking properties when processing carbon-black-filled conductive compounds (and also ICP blends) is the massive increase in melt viscosity compared with the unfilled matrix polymers and with other filled compounds, it is known that filled thermoplastics... 

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