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PROPERTIES OF MIRALON CNT Current-generation Miralon yarns have a tensile strength of 0.8-1 GPa, though next-generation products in development will double those values. Miralon yarns also have a strain to failure of 3.5%. The new CNTs have a density of 0.8 g/cc, about half that of carbon fiber. Thus, the material's specific tensile strength (per unit weight) is currently about half that of aerospace-grade carbon fiber or aramid fiber. But the next-genera- tion product could match or exceed both of these. When used in a composite, the current products already match or approach the strain to failure of aerospace carbon fibers such as IM7 and T1000. Those fibers may be stronger on their own, but suffer significant "knockdown" when incorporated into a composite. Miralon suffers no such knockdown, Antoinette asserts. He says NASA has produced thermoset composites with Miralon that have twice the specific strength of carbon-fiber composites. And, according to Antoinette, thermoplastics rein- forced with Miralon retain up to 98% of the fiber's original strain to failure. "Our CNT loves thermoplastics," he says, referring to good bonding with a variety of resins. What's more, Miralon yarn is very flexible, with high strength retention when tied into a knot, unlike carbon fiber. Because of its network structure, it also has a very high surface area, avail- able for bonding to resin and/or for transmitting heat or elec- tricity. Its flexibility/ductility is also valuable in soft body armor and reportedly will not suffer fatigue fracture even at cryogenic temperatures. The CNTs are also said to be highly resistant to radiation, salt, moisture, and corrosive conditions. Thermal and electrical conductivity are also outstanding properties of Miralon CNTs. According to Antoinette, as little as 0.02-0.05% Miralon can provide electrostatic dissipation (ESD) properties. In an adhesive application, Antoinette says, that compares with 0.15% graphene or 10% carbon fiber to provide ESD protection. EMI shielding can be provided by as little as 5% Miralon or a single layer of Miralon sheet 30-50 microns thick. Antoinette says Miralon's thermal conductivity can be appreciated by directing a torch flame at a composite sheet—the CNT fibers disperse the heat rapidly enough to resist melting or burning of the sheet. Miralon is also an infrared emitter. Antoinette demon- strates this with sheet of Miralon connected to an electric power source; a hand placed a few inches from the sheet feels emitted warmth almost immediately, but the sheet itself is barely warm to the touch. WHERE IT'S USED Thermoset composites (epoxy and cyanate ester) with Miralon have been qualified for aerospace use. Miralon sheet is used in a composite radiation/ESD shield and protective EMI layer on Pellets of Miralon CNT dispersed in a variety of thermoplastics can be injection or compression molded. In a high-temperature reactor, alcohol is injected into a hydrogen atmosphere with iron catalyst, yielding a continuous, hair-like "sock" of entangled CNTs. QUESTIONS ABOUT ADDITIVES? Visit the Additives Zone. Potential in thermoplastic molding compounds and 3D-printing filaments. 14 APRIL 2017 Plastics Technology PTonline.com C A R B O N N A N O T U B E S Close -Up On Technolog y