CompositesWorld
Issue link: https://cw.epubxp.com/i/632301
FEBRUARY 2016 30 CompositesWorld WORK IN PROGRESS This abundant, renewable resource shows promise as an alternative to PAN for low-cost, functional carbon fibers. Alternative precursor R&D;: Lignin in the lightweighting limelight ยป Aerospace-grade carbon fber's remarkable properties come at a steep price, compared to steel and aluminum. Tat's true, in part, because the process for converting high-performance precursor fbers into aerospace-grade structural carbon fber is rigorous and very energy-intensive. But it is also true that production of the polyacrylonitrile (PAN) precursor fber from which carbon fber is made accounts for at least 50% of the fnal carbon fber product. Te PAN fber itself is expensive and then there is the factor of chemical yield: it takes about 2 kg of precursor to yield, after carbonization, 1 kg of fnished carbon fber, a big contributor to carbon fber's high per-kilogram cost (see "Learn More," p. 34). For decades, investigators have looked for less costly, yet still carbon- rich, materials that could stand in for aerospace-grade precursor, and thus enable wider use of carbon fber in applications where the fber's light weight is desirable, but less-than-aerospace-grade properties would be acceptable. Tose investigations have yielded many options for usable carbon fbers, involving myriad aromatic chemistries, and hundreds of patents have been granted, dating back to the 1950s (see the Side Story on p. 34). "Alternative precursors have been Alternative precursor: More than a lab project The search for an alternative to PAN is no small undertaking. This carbon fber line at Oak Ridge National Laboratory's (Oak Ridge, TN, US) Carbon Fiber Technology Facility (CFTF), one of several research locales, is designed to handle not only aerospace-grade PAN, but textile-grade PAN and non-PAN precursors as well (see the Side Story on p. 31). One non-PAN alternative, lignin, must frst be harvested, processed and then spun into continuous fber like that shown here, produced by forest R&D; frm Innventia (Stockholm, Sweden). Source (top) | ORNL / (above) | Innventia By Sara Black / Technical Editor