Another Interesting Article on ElectriPlast
Plastics: Convincingly Conductive
Heater coils often use a 19-gage single wire, the ElectriPlast equivalent has 114 times the surface area.
Polymer material mimics metal.
A new moldable conductive polymer that can mimic metal in terms of its electrical conductivity and thermal abilities has been developed for use in myriad applications such as antennas, heat generation, shielding, and more than 100 other uses.
Developed by Integral Technologies, Bellingham, Wash., the material is called ElectriPlast. The polymer, which recently was awarded an innovations award from the Consumer Electronics Association, is a pelletized material that can be adapted for use with the more than 15,000 resins on the market today. It is the first conductive matrix in the plastic industry that can run household current as does copper, says chief technology officer Thomas Aisenbrey, the inventor of the material.
ElectriPlast versions vary depending on its composition, or recipe as the company calls it, and are available for injection molding, rotational molding, compression molding and extrusion, Aisenbrey says. By molding conductive parts, Aisenbrey says that they can be made at a lower cost than if they were made by traditional metal fabrication methods such as machining or casting. In addition, the precision of plastic injection molding typically eliminates most secondary operations associated with many metal fabrication processes.
Currently, the company has received more than 19 patents for the ElectriPlast material and more than 100 applications are in the patent pipeline. Company CEO Bill Robinson believes that the outstanding patents will be approved over the next couple years, and that additional patents will be made as new uses are discovered. Some of the newest patents relating to the ElectriPlast include PlastiCap, PlastiProbe, PlasTenna-No. 6, PlastiRFID, PlastiCooler, PlastiShield and PlastiShrink.
Its varied uses are highlighted by two licensing agreements that the company has entered into. In September, Jasper Rubber Products Inc., Jasper, Ind., finalized a licensing agreement to incorporate ElectriPlast into its products. The company makes molded, extruded, lathe-cut rubber and thermoplastic products for appliance, oil filter and automotive industries.
Another agreement was signed with Heatron Inc. of Leavenworth, Kan., which licensed the technology for use in its heating and LED lighting components. The contract manufacturer is currently researching how to best incorporate the material into its products and hopes to have some new products ready sometime in 2007.
The material’s thermal properties are one of its most important attributes, Aisenbrey says, allowing it to be used as a radiant heating element. Potential applications can range from towel racks, radiant heat flooring and car heaters. According to Aisenbrey, good thermal conductors such as copper have a thermal conductivity of 368 watts per meter Kelvin, while many ElectriPlast recipes surpass 650 watts per Kelvin, and another recipe meets 1,100 watts per meter Kelvin.
“We create so much more surface areas with our product that we get a lot better watt density with less power,” he adds. “If you have one wire that is acting as a heating element, or one particular element, than that is the only path for heat. We have a matrix with 10,000 paths.”
Ready to use
PlasTenna, the first use of the ElectriPlast technology, eliminates the need for separate antenna component.
ElectriPlast comes to the end user in ready-to-use, no-mix pellets. The pellets are formed prior to shipping by mixing the specified resin with the correct ElectriPlast recipe. As Aisenbrey puts it, everything that the manufacturers needs is in that pellet.
The material is made from conductive loaded resin-based materials that are made from conductive powders, micron conductive fibers, or a combination of them. The micron powders can be of carbons, graphites, amines or other materials, or metal powders such as nickel, copper, or silver.
The mix forms a matrix structure of tens of thousands of micron conductors that act in parallel with one another to form a highly conductive polymer, which contains and allows movable charges of electricity.
Because the material itself is conductive, the molded components are conductive. Aisenbrey says that gives more surface area on which electrons can travel and creates a broader area that designers can use. For instance, heater coils often use a single wire to conduct energy. In comparison to say using a 19-gage wire, the ElectriPlast equivalent has 114 times the surface area.
Most of the ElectriPlast recipes are non-corrosive and strong, yet light, he says. It is 80 percent lighter than copper and 40 percent lighter than aluminum. Aisenbrey says that most ElectriPlast formulations have specific gravity ratios of 1.64, with some formulations as low as 1.2, as compared to copper at 8.95 and aluminum at 2.71
When molded, the material typically has a range of resistivity from between about 5 and 25 ohms per square, but other resistivities can be achieved by varying the doping parameters or resins.
Diverse properties
ElectriPlast material is light, as shown in this specific gravity comparison.
Varying the dopant and resin types and levels can also give the material a variety of properties. For instance, it can be made resistant to corrosion or metal electrolysis by combining a corrosion and electrolysis resistant base resin with a stainless-steel fiber and carbon fiber and powder to create a resistant material. Or, the material can be made flame retardant by selecting a flame-retardant base resin material that will be mixed with the ElectriPlast recipe. One of the company’s many patents is for low-cost energy absorbers that can be used in products that might suffer from EMI issues. In this case, a loaded resin-based material can be interfaced to an electrical circuit or grounded. As an example, a wire can be attached to the electromagnetic energy absorbing materials by a screw such as a sheet-metal, self-tapping screw. To make this approach easier, a boss may be molded into the material to accommodate a screw. Alternatively, if a solderable screw material, such as copper, is used, then a wire can be soldered to the screw that is embedded into the conductive loaded resin-based material.
In another instance, a cloth-like material can be fabricated with random or continuous webbed micron stainless steel fibers or other conductive fibers, forming a conductive cloth like material. When using conductive fibers as a webbed conductor as part of a laminate or cloth-like material, the fibers may have diameters of between about 3 microns and 12 microns, typically between about 8 microns and 12 microns or in the range of about 10 microns, with length that can be seamless or overlapping.
Got lucky
Aisenbrey says that the uses for the material are nearly endless, limited only by the designer’s imagination.
The original use for the material was for antennas, a product the company dubbed PlasTenna, says Robinson. The company began developing the material when looking for a replacement part for a flat-panel antenna that they were developing for a satellite company. They had been using galvanized sheet stock for the various sizes of panels, but after cutting they worried about rusting issues.
Aisenbrey had done previous research on conductive polymers and felt that that could be a solution. After researching the marketplace, he says that he could not find a material on the market that was conductive enough and began working on what would become ElectriPlast.
Robinson says that after a lot of research they got “lucky” and struck on the appropriate recipe: “If you load the resin properly, it works. If you go too low, you are not going to get the same conductive properties. Too high, you lose the integrity of the batch. There is a sweet spot and we got lucky after a few months of trial and error.”
