RSS_Auto_Poster
Well-known member
Written by Steven Ashley
Carbon fiber isto composites as steel rebar is to concrete. When a support skeleton of eitheris embedded inside a solidifying mass of resin or cement, the strong sinews bindeverything together into a resilient, ultra-functional whole. But just as buildingcontractors have to charge more if rebar prices rise, the same goes for the makersof carbon-fiber composites. Trouble is, carbon fiber always has been too pricey.Although automotive OEMs expect to get carbon fiber at somewhere around $5 per pound, reportedSanjay Mazumdar, CEO at market consultants Lucintel in January, the marketprice ranges from $10 to $15 per lb. Carbon fiber"s premium pricetag derives mainlyfrom three factors: high precursor costs, high energy consumption andlong processing times during the fiber-conversion process. But that couldchange if a new, lower-cost manufacturing method achieves full industrial commercialization: a novel cold plasma-based processing technology, developed byresearchers at Oak Ridge National Laboratory (ORNL) and RMX Technologies ofKnoxville, Tenn., can dramatically cut the time and energy that"s expended onthe carbon fiber production line, said co-inventor and ORNL principalinvestigator Felix Paulauskas. Paulauskasdeveloped the basic concept for the method eight years ago and worked with RMXto develop prototypes and demonstrate the technology at the laboratory scale. In 2014,RMX constructed a 1-metric ton plasma oxidation oven (see http://articles.sae.org/11104/). Plasma magic The ORNL/RMXplasma-processing technology aims to improve what"s called the oxidation stageof the conversion process, said Truman Bonds, the co-developer and RMX plasmaengineer, who"s been Paulauskas" partner over the last decade. The oxidationline is where the precursor rows of polyacrylonitride (PAN) polymers are unrolledinto oven chambers to be oxidized (or stabilized), he explained. Oxidization isneeded for the fiber to survive the next step in the sequence in which it iscooked down to pure carbon, first at low, then at high temperatures from 1,000to 1,700 C. "Duringoxidation, the thermoplastic PAN precursor is essentially converted to athermoset material that can no longer be melted," Bonds said. But it"s a slowreaction. Oxidation is the most time-consuming and costly phase of production."It"s also the number one source of problems in the conversion process." "It takes a conventionalsystem somewhere between 75 and 120 min to full oxidization," Paulauska noted. "Ourplasma process cuts the time by a factor of 2.5 to 3 times, so we can processfiber in 25 to 35 min. And that"s with equal or better mechanical properties. Reactive ionicwind The patentednon-thermal, or cold plasma, technology creates a plasma "a fourth state" of weaklybonded matter, Bonds said. "It"s a collection, or cloud, of charged ions andelectrons that we create using applied electric fields. "The trick that weinvented is a way to generate the specific type of plasma chemistry we needdirectly from the air," he continued. "We can make a special reactive,oxidative bath that can accelerate the oxidation process at atmosphericpressure, tripling throughput." The plasmas helpherd clouds of reactive and so short-lived chemical species to the fibersurfaces where they can accelerate the diffusion of oxygen and push the oxidationreaction toward the fibers" centers. "Using fields we can create thermal flows,or use convective forces to induce the gases to move where we want and thenkeep them in place," he said. "The new technology could mean using 75% lessenergy per pound of fiber processed, saving 20% in costs." The new processhad been proven in the pilot-plant by five unidentified fibermanufacturers which then requested further demonstration at a larger scale, theyreported. RMX has licensed the technology and plans to build a plant with a 15,000-lb capacity to show feasibility for mass production. Meanwhile, an RMX subsidiarycalled 4M Industrial Oxidation has partnered with C.A. Litzler, a Cleveland-basedindustrial dryer and oven maker, to design and build 175-metric ton oven designby 2017; the subsidiary plans to sell the oven to at least eight prospective industrialcustomers. Low-cost PAN precursor "What the autoindustry needs to grow while growing greener is industrial-grade fiber at anacceptable price," Bonds said. "Our oxidation process gets you a 20% costreduction, but more is needed. That"s why we"re working with acrylic textilemaker Dralon of Lingen, Germany, who"s got a cheaper textile-grade PANprecursor that can be optimized for plasma oxidation." The resulting industrial-gradefiber is to provide 600-ksi tensile strength what"s needed for automotiveapplications. The textile precursor will bring another 20% cost reduction, hepredicted. The combinationof the two technologies could mean big value on any investments by the industry,said Rodney Grubb, RMX"s president. "A conventional plant produces a couple ofmillion pounds of carbon fiber a year. The combination looks like it could save$2 to $3 per lb so that"s worth multiple millions of dollars per year per line." Bonds added thatRMX has initiated development of new plasma-based and related technology that couldreduce the production costs accrued in the other two main stages of thefiber-conversion process carbonization and surface treatment (that is, the use ofsizing powders as a matrix-bonding interface and materials-handling aide). Bothefforts are at the early stage. For surface-treatment work, researchers are studying the use of atmospheric-pressure plasmas that help low-cost sizings and resins to better bond with thecarbon fiber"s outer skin, which has been rendered almost entirely chemicallyinert by carbonization. Although it"s still early days, Grubb said, RMX has identifiedsome performance and efficiency advantages over the standard wet-chemical-dip ("washand dry"), or thermochemical processing techniques.
Date written: 11-Jun-2016 05:15 EDT
More of this article on the SAE International Website
ID: 3802
Carbon fiber isto composites as steel rebar is to concrete. When a support skeleton of eitheris embedded inside a solidifying mass of resin or cement, the strong sinews bindeverything together into a resilient, ultra-functional whole. But just as buildingcontractors have to charge more if rebar prices rise, the same goes for the makersof carbon-fiber composites. Trouble is, carbon fiber always has been too pricey.Although automotive OEMs expect to get carbon fiber at somewhere around $5 per pound, reportedSanjay Mazumdar, CEO at market consultants Lucintel in January, the marketprice ranges from $10 to $15 per lb. Carbon fiber"s premium pricetag derives mainlyfrom three factors: high precursor costs, high energy consumption andlong processing times during the fiber-conversion process. But that couldchange if a new, lower-cost manufacturing method achieves full industrial commercialization: a novel cold plasma-based processing technology, developed byresearchers at Oak Ridge National Laboratory (ORNL) and RMX Technologies ofKnoxville, Tenn., can dramatically cut the time and energy that"s expended onthe carbon fiber production line, said co-inventor and ORNL principalinvestigator Felix Paulauskas. Paulauskasdeveloped the basic concept for the method eight years ago and worked with RMXto develop prototypes and demonstrate the technology at the laboratory scale. In 2014,RMX constructed a 1-metric ton plasma oxidation oven (see http://articles.sae.org/11104/). Plasma magic The ORNL/RMXplasma-processing technology aims to improve what"s called the oxidation stageof the conversion process, said Truman Bonds, the co-developer and RMX plasmaengineer, who"s been Paulauskas" partner over the last decade. The oxidationline is where the precursor rows of polyacrylonitride (PAN) polymers are unrolledinto oven chambers to be oxidized (or stabilized), he explained. Oxidization isneeded for the fiber to survive the next step in the sequence in which it iscooked down to pure carbon, first at low, then at high temperatures from 1,000to 1,700 C. "Duringoxidation, the thermoplastic PAN precursor is essentially converted to athermoset material that can no longer be melted," Bonds said. But it"s a slowreaction. Oxidation is the most time-consuming and costly phase of production."It"s also the number one source of problems in the conversion process." "It takes a conventionalsystem somewhere between 75 and 120 min to full oxidization," Paulauska noted. "Ourplasma process cuts the time by a factor of 2.5 to 3 times, so we can processfiber in 25 to 35 min. And that"s with equal or better mechanical properties. Reactive ionicwind The patentednon-thermal, or cold plasma, technology creates a plasma "a fourth state" of weaklybonded matter, Bonds said. "It"s a collection, or cloud, of charged ions andelectrons that we create using applied electric fields. "The trick that weinvented is a way to generate the specific type of plasma chemistry we needdirectly from the air," he continued. "We can make a special reactive,oxidative bath that can accelerate the oxidation process at atmosphericpressure, tripling throughput." The plasmas helpherd clouds of reactive and so short-lived chemical species to the fibersurfaces where they can accelerate the diffusion of oxygen and push the oxidationreaction toward the fibers" centers. "Using fields we can create thermal flows,or use convective forces to induce the gases to move where we want and thenkeep them in place," he said. "The new technology could mean using 75% lessenergy per pound of fiber processed, saving 20% in costs." The new processhad been proven in the pilot-plant by five unidentified fibermanufacturers which then requested further demonstration at a larger scale, theyreported. RMX has licensed the technology and plans to build a plant with a 15,000-lb capacity to show feasibility for mass production. Meanwhile, an RMX subsidiarycalled 4M Industrial Oxidation has partnered with C.A. Litzler, a Cleveland-basedindustrial dryer and oven maker, to design and build 175-metric ton oven designby 2017; the subsidiary plans to sell the oven to at least eight prospective industrialcustomers. Low-cost PAN precursor "What the autoindustry needs to grow while growing greener is industrial-grade fiber at anacceptable price," Bonds said. "Our oxidation process gets you a 20% costreduction, but more is needed. That"s why we"re working with acrylic textilemaker Dralon of Lingen, Germany, who"s got a cheaper textile-grade PANprecursor that can be optimized for plasma oxidation." The resulting industrial-gradefiber is to provide 600-ksi tensile strength what"s needed for automotiveapplications. The textile precursor will bring another 20% cost reduction, hepredicted. The combinationof the two technologies could mean big value on any investments by the industry,said Rodney Grubb, RMX"s president. "A conventional plant produces a couple ofmillion pounds of carbon fiber a year. The combination looks like it could save$2 to $3 per lb so that"s worth multiple millions of dollars per year per line." Bonds added thatRMX has initiated development of new plasma-based and related technology that couldreduce the production costs accrued in the other two main stages of thefiber-conversion process carbonization and surface treatment (that is, the use ofsizing powders as a matrix-bonding interface and materials-handling aide). Bothefforts are at the early stage. For surface-treatment work, researchers are studying the use of atmospheric-pressure plasmas that help low-cost sizings and resins to better bond with thecarbon fiber"s outer skin, which has been rendered almost entirely chemicallyinert by carbonization. Although it"s still early days, Grubb said, RMX has identifiedsome performance and efficiency advantages over the standard wet-chemical-dip ("washand dry"), or thermochemical processing techniques.
Date written: 11-Jun-2016 05:15 EDT
More of this article on the SAE International Website
ID: 3802
