Is there still a strong need for cellulosic precursor carbon fibers (CFs) for use in rocket nozzles?
The Defense Systems Information Analysis Center (DSIAC) was provided with a method to domestically produce fibers similar to viscose rayon fibers used historically in military missiles and NASA solid rocket motors (SRMs). As these fibers haven’t been produced since the 1990s due to environmental and financial sustainability concerns, DSIAC was tasked with determining whether there is a current need for such a manufacturing process to exist in the defense community. To help answer this question, DSIAC contacted subject matter experts (SMEs) from Tri-Austin, Johns Hopkins University (JHU) Energetics Research Group (ERG), National Renewable Energy Laboratory (NREL), Oak Ridge National Laboratory (ORNL), and various academic institutions. An overview of cellulosic carbon fiber and involved/interested research organizations is compiled below with additional relevant publications available for further reading in the bibliography.
1.1 Cellulosic Precursor Carbon Fibers (CFs)
Cellulosic fibers were first introduced to the market in the 1960s and were produced from rayon. Rayon is a natural, cellulose-based material (e.g., wood pulp, cotton linters, leaves, inner pith of bamboo plants, etc.) that is chemically processed to produce semisynthetic fibers. Even though the raw materials cost is lower for rayon-based fibers, a lower yield pushes production costs above polyacrylonitrile (PAN)-based CFs. This fact is one of the reasons that rayon-based CFs have limited commercial production (1−2% of all CF production). Due to lower tensile strengths than PAN-based CFs, rayon-based CFs are not used in structural applications. Instead, rayon fibers are used in the rocket and missile industries for ablative applications (e.g., heat shields and rocket nozzles) since the fibers can withstand high temperatures and the erosive gases of SRMs. There are two required stages and one optional stage of production. Stabilization of the precursor (i.e., low temperature oxidation) and carbonization (i.e., longitudinal orientation and development of the crystalline ordering) are required; graphitization is an optional stress that will increase the modulus of elasticity .
1.2 Potential Markets for Cellulosic Precursor CFs
Cellulosic CFs were classically used to form ablative rocket nozzles and heat shields. However, NARC ceased production of the fiber after it was unable to financially comply with Environmental Protection Agency (EPA) regulations. According to a CompositesWorld article, NASA’s stockpile of NARC fiber has been dwindling since production of the fiber stopped in the 1990s. Therefore, new processes to create cellulosic CF could be of interest and used for SRMs in the next-generation Space Launch System .
Outside of ablative and thermal resistance applications, other countries (e.g., Japan, China, Australia, Finland, etc.) have explored other uses for cellulosic precursor CFs that may not require the high strengths of other CFs. Cellulose-based CFs for carbon-carbon composites (CCCs) could potentially be used in hypersonic reentry vehicles, rocket propulsion, and aircraft brakes . Widespread automotive and wind energy applications that do not require the >3 gigapascals (GPa) of ultimate tensile strength are offered by PAN-based CFs .
In Japan, researchers have been developing products with cellulose nanofibers such as disposable diapers and ballpoint pens, and cellulose nanofibers could potentially be used in food, cosmetics, and flexible displays. Cellulose nanofibers have also been used as a strengthening resin in rubbers and plastics . Furukawa Electric intends to use cellulose-based CFs for automotive interiors, electronics components, and body exterior panels, as part of the $3.5 billion market of replacing fiberglass composites . Chemviron Carbon, located in the United Kingdom, has used viscose rayon fibers for knitted or woven activated carbon fabrics (ACFs) as an adsorbent material in chemical protective clothing. Applications for ACFs include the following :
- Combat suits;
- First responder suits;
- Escape masks;
- Chemical, biological, radiological, and nuclear (CBRN) filtration media;
- CBRN decontamination wipes;
- Low weight reduced respirator canisters;
- Antimicrobial wound dressings;
- Missile decoy media.
Similarly, CF/cellulose composite papers were produced using papermaking techniques. Hot fibers were used to modify the CF/cellulose composite paper’s mechanical properties .
2.0 Subject Matter Expert Input
2.1 National Laboratories and Government Agencies
2.1.1 Oak Ridge National Laboratory (ORNL)
Two technology centers at ORNL have research focuses on CF development and advancement in partnership with the U.S. Department of Energy (DoE). The Carbon Fiber Technology Facility, housed at ORNL, allowed the Manufacturing Demonstration Facility and the National Transportation Research Center to focus on alternative precursors, advanced and energy-efficient conversion processes, and scaling. The thermal conversion line provided a baseline for standard modulus PAN, but was designed with the flexibility to accommodate lignin, polyolefin, and pitch precursors. It can also be readily upgraded to convert rayon and high-modulus PAN precursors [9, 10]. See Table 1 for more information on ORNL’s Manufacturing Demonstration Facility, and Table 2 for more information on ORNL’s National Transportation Research Center.
Table 1: ORNL Manufacturing Demonstration Facility Contact Information 
|Organization||Manufacturing Demonstration Facility|
|Address||2370 Cherahala Blvd
Knoxville, TN 37932
Table 2: ORNL National Transportation Research Center Contact Information 
|Organization||National Transportation Research Center|
|Address||2360 Cherahala Blvd.
Knoxville, TN 37932
2.1.2 National Renewable Energy Laboratory (NREL)
After finding multiple papers published on CF manufacturing by scientists at the National Renewable Energy Laboratory (NREL), DSIAC contacted a principal scientist at the National Bioenergy Center of NREL. However, the NREL research is focused on bioderived acrylonitrile (ACN), another precursor for CF, though NREL mentioned that Southern Research was exploring a cellulosic route to produce CF as a rayon replacement .
2.2 Industry and Private Organizations
2.2.1 Institute for Advanced Composites Manufacturing Innovation (IACMI)
With the assistance of ORNL’s Sustainable Transportation Program, DSIAC contacted the Director of the Materials and Process Technology Area at ORNL, who is located at IACMI.
The Director of the Materials and Process Technology Area stated that IACMI doesn’t know of a current potential market for CFs made from cellulosic precursors, though several research institutions are attempting to produce cellulose-based CFs that would satisfy a market need (i.e., the balance of cost and performance) and lead to future market development. See Table 3 for IACMI contact information.
A few other institutions conducting relevant research include the University of Tennessee-Knoxville, North Carolina State University, Iowa State University, Washington State University, and the University of British Columbia. Innventia in Sweden is also notable for its relevant research, and there is also interest in Scandinavia and Asia for CF manufacturing .
Table 3: IACMI Contact Information 
|Address||2360 Cherahala Boulevard
Knoxville, TN 37932
2.2.2 Texas Research Institute Austin (TRI Austin)
TRI Austin is a DSIAC subcontractor that brings significant laboratory and materials research and development (R&D) and testing experience to DSIAC . See Table 4 for the TRI Austin contact information.
Table 4: TRI Austin Contact Information 
|Address||9225 Bee Cave Rd.
Bldg B, Ste. 200
Austin, TX 78733
TRI Austin supplied papers of interest and contact information for other SMEs . The papers of interest include the following:
The paper “NARC Rayon Replacement Program for the RSRM Nozzle, Phase IV Qualification and Implementation Status” is a review of NASA’s selection process that took place in the mid-2000s to find a replacement for the out-of-production NARC rayon CF. NASA purchased a stockpile of the fiber prior NARC discontinuing rayon fiber production to support reusable solid rocket motor (RSRM) production but wanted to have a new supplier as the stockpile dwindled. After testing 21 cellulose fiber candidates, the fiber chosen for Phase III and IV testing was Acordis Enka CCP. Concerns at the end of testing included the supplies of pulp and recent closures of other rayon plants in Europe .
The NREL report “Carbon Fiber from Biomass” details different CFs using biomass sources. It notes that as of 2012, the RUE-SPA-Khimvolokno in Belarus is the main rayon-based CF producer in the world, that the U.S. DoD has a vested interest in the production of these fibers, and that there is research into the production occurring at the University of Tennessee using experimental fibers from Advanced Cerametrics in Lambertville, NJ and commercial fibers from Lenzing Group. The report also explores the economics of producing fibers in the U.S., especially without importing the precursors and, instead, importing the raw materials .
TRI Austin mentioned that Fiber Materials Inc. produces carbon-carbon extreme materials for applications such as solid rocket motor throats, leading edges, missile nose tips, nozzle exit cones, and aircraft brakes . Based on the sources provided, it is apparent that the U. S. has searched for a replacement for NARC as recently as 2005.
2.2.3 Johns Hopkins University (JHU) Energetics Research Group (ERG)
DSIAC contacted SMEs at JHU ERG who provided points of contact for multiple potentially knowledgeable people at various NASA groups, as well as information related to cellulosic CFs. JHU ERG contact information is presented in Table 5. Companies that produce cellulosic CFs include the following :
- Highland Industries: Highland Industries is a U.S. company that produces woven rayon fabrics for aerospace use. It began as an exclusive relationship more than 35 years ago for woven rayon fabrics that formed the insulators for solid rocket nozzles on the Space Shuttle .
- Lenzig Fibers Incorporated: According to the American Fiber Manufacturer’s Association, the only U.S. producer of Lyocell staple fibers is Lenzig Fibers Inc. .
- Morgan Advanced Materials & Technology: Morgan Advanced Materials & Technology is the only company that carbonizes Lyocell fibers .
The steps to create cellulosic rayon fibers are fiber production, weaving, prepregging, and carbonization. The process starts with Lenzig Fibers, Inc. , then moves to Highland Industries, and then to Morgan Advanced Materials & Technology. The University of Alabama-Huntsville (UAH) would come in as an alternate to Lenzig, or to whomever they license their technology .
The JHU ERG representatives also provided a U.S. Army Small Business Innovative Research (SBIR) report that describes the collaboration between the University of Alabama-Huntsville and MATECH on the fiber-production process .
Table 5: JHU ERG Contact Information 
|Address||10630 Little Patuxent Parkway
Columbia, MD 21044-3286
2.2.4 Southern Research
The following as an excerpt from the article “Southern Research Project Targets Low-Cost Carbon Fibers”:
Amit Goyal, Ph.D., is leading a team of scientists at Southern Research that has developed a cheaper and cleaner process for making acrylonitrile, a precursor for carbon-fiber production.
Goyal’s team has devised a multi-step catalytic process that converts sugars from non-food biomass to acrylonitrile through a pathway that could be around 20 percent cheaper than the typical production method. Their process also involves a substantial reduction in greenhouse gases.
The CFs produced from this raw biomass process could interest automakers, which are looking at composite materials to reduce the weight of vehicles.
Goyal, manager of Southern Research’s sustainable chemistry and catalysis group, Energy & Environment, North Carolina, acts as principal investigator on the $6 million Department of Energy study.
Southern Research is working with Cytec and the New Jersey Institute of Technology on the DoE-funded study .
2.3 Academic Institutions
2.3.1 University of Tennessee-Knoxville
The University of Tennessee-Knoxville has multiple publications related to cellulose-based CFs and has strong ties to ORNL and IACMI. The University of Tennessee-Knoxville received an EPA grant for 2004−2008 to develop cellulosic CF precursors from ionic liquid solutions. The grant resulted in three papers, one of which is included in the following list of publications of interest (third bullet) :
- In the presentation “Recent Developments on Carbon Fibers from Rayon-Based Precursors” from the 2013 Carbon Fiber Workshop in Buffalo, NY, Dr. G. Bhat’s research group presented on the possibility of producing rayon fibers due to the lack of domestic manufacturers. The research explored the possibility of using experimental rayon fibers supplied by Advanced Cerametrics Inc. as a CF precursor, while also using commercial rayon fibers from Lenzing. The initial observations included a need to improve the mechanical strengths and decrease the fiber diameters .
- In his master’s thesis, “Pretreatment and Pyrolysis of Rayon-Based Precursor for Carbon Fibers,” K. Akato investigated two different rayon fibers as CF precursors. The objectives of the work were to investigate the stabilized stage of the produced rayon and the changes occurring during thermal decomposition, and to evaluate the effects of these changes on the properties of the carbonized fiber. The changes that take place during the conversion of the domestic fibers were compared with commercial rayon fiber .
- The second article in a series of three, “Rheology of 1-Butyl-3-Methylimidazolium Chloride Cellulose Solutions. II. Solution Character and Preparation,” focuses on the effects of preparation and composition on the shear rheology of cellulose in the ionic liquid 1-butyl-3-methylimidazolium chloride. The effects of three different degrees of polymerization, manual versus high shear mixing, range of cellulose concentrations, and effects of controlled amounts of lignin and hemicellulose are included in the investigation. Conclusions include the implication from the rheology that a gel phase develops at higher degrees of polymerization, higher concentration, and at lower temperatures .
While the University of Tennessee-Knoxville has researched efforts into cellulosic precursor CF similarly to the University of Alabama-Huntsville, there are a few other universities (i.e., Iowa State University and Washington State University) that focus on sugar or biobased lignin CF precursors for ACN or PAN.
2.3.2 University of Texas
Per the suggestion of TRI Austin, DSIAC investigated Dr. Joseph Koo’s research group at the University of Texas at Austin. DSIAC determined that a plethora of Dr. Koo’s projects relate to ablation and CFs .
2.3.3 Iowa State University
The Polymer Composites Research Group at Iowa State University is investigating the viability of using lignin-based CFs in wind turbine blades [33, 34].
2.3.4 Washington State University
The Composite Materials & Engineering Center at Washington State University is researching synthesizing biobased ACN from propylene glycol [35, 36].
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