Conductive thermoplastic compounds

Conductive Thermoplastic Compounds. Conductive thermoplastic compounds were prepared using Eeonomers. Volume resistivity as a fimction of Eeonomer content is shown in Figure 4 for nylon-6 and ABS compounds. The volume resistivity is observed to fall several orders of magnitude between 5 and 10 wt % of composite concentration. This indicates that the resistivity is very responsive to Eeonomer loading level and that percolation is occurring within this range. 

For EMI shielding applications, numerous processes are used, some require conductive fillers. These applications include parts molded with conductive filler and conductive paints. Conductive fillers used in commercial applications include aluminum, silver, nickel, and copper flakes and powders, stainless steel fibers, and fibers and flakes coated by nickel and silver. Thermoplastic compounds can provide up to 65-70 dB of electromagnetic noise attenuation but obtaining values over 45 dB is difficult. Static dissipative compounds (ESD) are mostly produced with carbon black which accounts for approximately 90% of the market but many other fillers are also used. 

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. 

Hyperion Catalysis International markets its nanombes under the name Fibril . Adding 5% to polycarbonate transforms its volume resistivity from lO to 10 ohm-cm and, unlike some particulate additives, only reduces the tensile strength by 11%, while increasing the flexural modulus by 18%. One important application is the polyamide fuel lines in vehicles, and another is the production of the conductive thermoplastic fenders used for in-line electrostatic painting. In the case of fuel lines, the compounding system must produce highly homogeneous compositions to rule out local static build up. Less than one per cent of nanotubes is sufficient. 

The principal fillers used for molding compounds and other thermoset and thermoplastic compounds can be classified as (1) agricultural and plant products, (2) conductive fillers, (3) fibrous fillers, (4) mineral fillers, and (5) reclaimed material. 

Electrablend, Electrically active injection mold-able compounds, TP Composites, Inc. Electrafil, Conductive thermoplastics, DSM Engineering Plastics... 

Stat-Kon, Fortified static-conductive thermoplastics, LNP Engineering Plastics Inc. Stat-Loy, Antistatic compounds, LNP Engineering Plastics Inc. 

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. 

In more recent work, a composition which was claimed to be fusible and melt-extrudable was developed in a joint effort of UNIAX Corp., Santa Barbara, CA, USA, and Neste Oy, Porvoo, Finland, given the tradename PANIPOL [278]. In its typical preparation, a sulfonated P(ANi) salt, a plasticizer, and other "optional additives" are fed into a twin-screw extruder with a typical temperature profile along the screw of between 100 and 180 °C and residence time 5 to 10 mins. The resulting conductive strands are cooled, pelletized and packaged. The conductive pellets are then compounded for such end uses as injection molded articles or extruded films and fibers, or any other conductive thermoplastic products. The authors also claimed to have demonstrated conductive thermosets based on solution-processed PANIPOL. 

Power Cables. The materials mosdy used to produce power cables are ethylene copolymers loaded with conductive carbon black for semiconductive shielding layers, polyethylene or ethylene—propylene mbber-based compounds as insulations, and either thermoplastic materials (eg, polyethylene, PVC) or thermosetting (based on chlorinated polyethylene (CPE), chlorosulfonated polyethylene (CSPE), chloroprene, etc) for jackets. 

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. 

Polyurethane pre-polymer or thermoplastic polyurethanes are prepared by the reaction of polyester or polyether diols with diisocyanates. The reaction can be conducted in bulk, in a solvent, or in an aqueous solution or dispersion. Unless the reaction is carried out at an elevated temperature a catalyst is required. Organotin compounds are the prime catalyst for this reaction. 

Polymeric compounds are specific sealing materials intended to line or impregnate conducting hardware as well as electric radio circuits for electric insulation. They are based on epoxy and unsaturated polyester resins, liquid organosilicon rubbers and monomers (initial products for S3mthesizing pol3Tnethacrylates and polyurethanes). Compounds based on thermoplastic materials (tar, rosin, cerezin) in the form of solid or wax-like masses, heated for transformation into the liquid state, are confined to this application. 

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