Carbon Fiber Production Research Articles

Bio-cleaning improves the mechanical properties of lignin-based carbon fibers.

Production of carbon fibers (CF) using renewable precursors has gained importance particularly in the last decade to reduce the dependency on conventional petroleum-based precursors. However, pre-treatment of these renewable precursors is still similar to that of conventional ones. Little work is put into greener pre-treatments and their effects on the end products. This work focuses on the use of bio-cleaned lignin as a green precursor to produce CF by electrospinning. Bio-cleaned kraft lignin A (Bio-KLA) and uncleaned kraft lignin A (KLA) were used to explore the effect of bio-cleaning on the diameter and mechanical properties of lignin fibers and CF. The effect of electric field, lignin-to-poly(ethylene oxide) (PEO) ratio and PEO molecular weight (MW) were evaluated by 33 factorial design using Design of Experiment (DOE). The electrospinning process parameters were optimized to obtain a balance between high elastic modulus and small fiber diameter. The model predicted optimized conditions were 50 kV m−1 electric field, 95/5 lignin-to-PEO ratio and 1000 kDa MW of PEO. When compared to KLA, Bio-KLA CFs showed a 2.7-fold increase in elastic modulus, 2-fold increase in tensile strength and 30% decrease in fiber diameter under the same optimum conditions. The results clearly show that bio-cleaning improved the mechanical properties of lignin derived CF.

Lignin from oil palm empty fruit bunches (EFB) under subcritical phenol conditions as a precursor for carbon fiber production

Sustainable approach is needed to find an alternative precursor for carbon fiber. The resources should be low in cost with properties comparable to the present precursor. Malaysia as the second largest producer of palm oil produced hundred million tons of waste especially oil palm empty fruit bunches (EFB) from its plantation. The extraction of its lignin from biomass is a challenge as it binds together with cellulose and hemicellulose to form a complex network. Hence, phenol under subcritical conditions has the potential to shorten the reaction time to dissolve relatively high molecular weight compounds without catalyst. This study aimed to determine the effect of temperature (260–300 °C), reaction time (1–10 min), and solid loading (6 and 10 g) towards ash, volatile and carbon content of the lignin obtained from EFB under subcritical phenol conditions. Highest carbon content in the lignin (43.7%) was achieved at 260 °C, 1 min, and 10 g while its ash and volatile content were 23.5% and 0.3% respectively. The correlation of these properties is discussed in this paper to understand its suitability as a precursor for carbon fiber production.

Thermal treatment of pyrolytic lignin and polyethylene terephthalate toward carbon fiber production

ABSTRACTIn this work, pyrolytic lignin (PL) was thermally co‐treated with polyethylene terephthalate (PET) to produce carbon fiber precursor. The produced PL‐PET precursors were thoroughly characterized and analyzed, and then being processed into carbon fiber. It was found that a novel precursor, rather than their physical blending, was formed by the thermal co‐treatment, indicating there were strong interactions between PL and PET. The novel PL‐PET precursors had enhanced thermal properties and rheological characteristics, therefore are more suitable for processing into better carbon fibers based on melt‐spinning method. In this study, the precursor fibers derived from the co‐treatment of PL and 5% PET were also stretched under tension during stabilization step to reduce the fiber diameter and improve molecular orientation. The resulting carbon fibers with an average diameter of 12.6 μm had the tensile strength of up to 1220 MPa. This work demonstrated that PET could be used to improve the processability and quality of lignin‐based carbon fiber when it is chemically bonded with lignin‐based precursor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48843.

Pyrolysis of brominated polyethylene as an alternative carbon fibre precursor

Polyethylene as a polymeric precursor for carbon fibre production has attracted much attention over recent years. Not only is it a low-cost commodity polymer, it has a higher theoretical carbon yield (at 100%) than polyacrylonitrile (at 67%) and is very readily melt processed into fibres. The challenge is to efficiently dehydrogenate and graphitize polyethylene fibres. This paper explores the use of bromine as a novel oxidant to functionalise polyethylene prior to carbonisation, leading to efficient cyclisation and carbonisation on heating. Through a process of low-temperature photo-induced liquid-phase bromination followed by dehydrobromination at moderate temperature and subsequent carbonisation to 800 °C, a carbonaceous product was obtained in high carbon yield (>90%). The effects of a range of process conditions, as well as the use of different types of polyethylene and polyethylene blends, were explored.

Kinetics of the cyclization and isomerization reactions in polyacrylonitrile based carbon fiber precursors during thermal‐oxidative stabilization

ABSTRACTThe kinetics of reactions in polyacrylonitrile (PAN) based carbon fiber (CF) production should be of significance to the guidance of process control, fiber structure formation. PAN precursor fibers were isothermally stabilized at 210, 225, 240, 255, and 270 °C, respectively, for 10 to 100 min in an air oven to study the kinetics of the cyclization and isomerization reactions. The structural evolution of PAN precursor fibers during thermal‐oxidative stabilization was characterized by Fourier transform infrared (FTIR) spectroscopy and solid state 13C nuclear magnetic resonance (13C NMR). The results indicate that the FTIR absorbance of CN (the resultant of the cyclization) in PAN shows a trend of first increasing and then decreasing. And then the NMR peak assigned to the carbon atoms linking imino groups (NH) proves the isomerization of CN into NH in pyridone structure. Based upon the FTIR absorbance method, the entire process of the cyclization and isomerization reactions is considered as a consecutive first‐order reaction. A kinetic model for the consecutive reaction has been established via the evaluation of the reaction rate constants of two single reactions. According to the model, the simulated kinetic curves of the characteristic groups (CN, CN, and NH) conform to the FTIR absorbance trends of these groups based on experimental data. This study is expected to furnish in‐depth information on the crucial reaction kinetics during stabilization of PAN precursors, which is of advantage to the process optimization of the CF production. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48819.

Predicting cost-effective carbon fiber precursors: Unraveling the functionalities of oxygen and nitrogen-containing groups during carbonization from ReaxFF simulations

Blends of polyacrylonitrile (PAN) and poly(p-phenylene-2,6-benzobisoxazole) (PBO) as precursors may offer an opportunity to reduce the cost of carbon fiber (CF) production. The all-carbon ring formations and volatile gas production during the heating and carbonization for 9 PAN/PBO blend precursors with varying mixing ratios are studied via the ReaxFF reactive molecular dynamics simulations. Evolutions of oxygen-containing (O-containing) and nitrogen-containing (N-containing) groups are detailed, in order to reveal the reaction mechanisms of the O and N-based CF precursors. Particularly, the O-containing groups are identified to be more efficient for initiating the carbonization, whereas N-containing groups are far longer retained in the graphitic materials and play a key role in capturing and converting carbon radical species into the graphitic networks. Additionally, the PAN/PBO blend precursor with a mole ratio of 1:1 is compared with the pre-oxidized PAN, PAN, and PBO. It is found that the PAN/PBO blends could be a promising alternative for the cost-effective PAN-based CF precursors, since they can decrease the cost of the CF production by means of: (a) eliminating the pre-oxidation process, (b) having considerable all-carbon ring formations within a short period, and (c) having a relatively fast conversion rate, reaching 95% 6-membered carbon ring formation.

Characterization of Wood-based Industrial Biorefinery Lignosulfonates and Supercritical Water Hydrolysis Lignin

Understanding the properties of any particular biorefinery or pulping residue lignin is crucial when choosing the right lignin for the right end use. In this paper, three different residual lignin types [supercritical water hydrolysis lignin (SCWH), ammonium lignosulfonate (A-LS), and sodium lignosulfonate (S-LS)] were evaluated for their chemical structure, thermal properties and water vapor adsorption behavior. SCWH lignin was found to have a high amount of phenolic hydroxyl groups and the highest amount of β-O-4 linkages. Combined with a low ash content, it shows potential to be used for conversion into aromatic or platform chemicals. A-LS and S-LS had more aliphatic hydroxyl groups, aliphatic double bonds and C=O structures. All lignins had available C3/C5 positions, which can increase reactivity towards adhesive precursors. The glass transition temperature (Tg) data indicated that the SCWH and S-LS lignin types can be suitable for production of carbon fibers. Lignosulfonates exhibited considerable higher water vapor adsorption as compared to the SCWH lignin. In conclusion, this study demonstrated that the SCWH differed greatly from the lignosulfonates in purity, chemical structure, thermal stability and water sorption behavior. SCWH lignin showed great potential as raw material for aromatic compounds, carbon fibers, adhesives or polymers. Lignosulfonates are less suited for conversion into chemicals or carbon fibers, but due to the high amount of aliphatic hydroxyl groups, they can potentially be modified or used as adhesives, dispersants, or reinforcement material in polymers. For most value-adding applications, energy-intensive purification of the lignosulfonates would be required.Graphic

Wet-spinning of Cellulose Acetate Reinforced with Acetylated Nano-crystalline Cellulose as Carbon Fibre Precursors

The search precursors that are bio-based, renewable and biodegradable has attracted significant attention due to increased environmental awareness. Recently, nano-crystalline cellulose (NCC) has been considered as a potential precursor to produce carbon fibre owing to its high crystallinity and excellent mechanical properties. However, its crystallinity prevents it from being dissolved in comment solvents. The main aims of this study were: (i) to acetylate NCC to improve its compatibility with cellulose acetate and (ii) to produce wet-spun cellulose acetate fibres reinforced acetylated and unacetylated NCC. In this study, rod-like particles of NCC with diameters in the range 2.0-4.8 nm and lengths of 46-114 nm were characterised using a Transmission Electron Microscope (TEM). The carbonyl (C=O) group of the acetyl group was confirmed using Fourier Transmission Infrared (FTIR), and the crystallinity of NCC was characterised using X-Ray Diffraction (XRD). The crystallinity indicates of the NCC before and after acetylation were 78% and 68% respectively. The morphology of wet-spun cellulose acetate reinforced acetylated NCC was smoother than reinforced NCC. The acetylation on NCC increased its compatibility with the polymer matrix.

Study on the Effect of Reaction Temperature, Time, and Solid Loading on Lignin from Oil Palm Frond (OPF) under Subcritical Phenol Conditions as a Precursor for Carbon Fiber Production

Study on the Effect of Reaction Temperature, Time, and Solid Loading on Lignin from Oil Palm Frond (OPF) under Subcritical Phenol Conditions as a Precursor for Carbon Fiber Production

Development of a cost model for the production of carbon fibres

Carbon fibre composites offer considerable potential for mass reduction in automotive applications. However, raw material cost is one of the major factors that constraints its extensive use in this mass market. Here we report a systematic study that presents the cost contributors by considering the entire process chain of the carbon fibre manufacturing. The sensitivity analysis revealed that the final cost of Polyacrylonitrile (PAN) precursor and carbon fibres were strongly influenced by tow size. It was observed that a prompt decrease in the precursor and carbon fibre cost per kg for tow sizes from 3k to 12k, later this decrement was gradual and almost became stable above 50k. Moreover, with an increase in tow size from 3k to 50k, the contribution of the precursor on the final carbon fibre cost decreased from 76.6% to 49.6%. On the other hand, the contribution of the other factors increased with increase in the tow size, for instance, labour (9.86%–17.78%), Energy (2.49%–6.48%) and Depreciation (6.11%–11.01%). Nevertheless, precursor holds the major share in determining the final price of the carbon fibres.

Investigation of the potential for utilization of sugarcane bagasse lignin for carbon fiber production: Thailand case study

Lignin is an attractive biomaterial to replace petroleum aromatics due to its intrinsic aromatic structure and availability. In Thailand, the sugar industry has potential as a source of around 7.5 million tons of lignin per annum. Sugarcane bagasse lignin was developed as a low-cost precursor in carbon fiber production to replace polyacrylonitrile, a petroleum-derived polymer using the electrospinning technique. A technical study and financial assessment of carbon fiber production feasibility from bagasse lignin at the laboratory scale were performed in parallel, and the Thai carbon fiber market was surveyed. Results showed that electrospun carbon nanofiber could be produced from a mixture of 25% lignin and 75% polyacrylonitrile with diameter of 171 nm. The surface area of carbon nanofiber produced from lignin-polyacrylonitrile mixture was higher than that of pure polyacrylonitrile. However, increasing lignin content in the mixture resulted in lower conductivity. Lignin-polyacrylonitrile carbon nanofiber obtained was appropriate for those where higher surface area was required rather than structural application. A market survey indicated increasing exploitation of carbon fiber in Thailand during the last 5 years even though there was no industrial production of carbon fiber due to technical and financial constraints. Both carbon nanofiber and lignin production costs at laboratory scale (12.4 $/g) were 27 times lower compared to commercial carbon nanofiber (343.4 $/g) available in a similar form. This price difference presents an opportunity to further development of carbon nanofiber for industrial application, although intensive research and development are still required.

Effect of Mo on the catalytic activity of Ni-based self-organizing catalysts for processing of dichloroethane into segmented carbon nanomaterials

A series of micro-disperse Ni-Mo alloys with the sponge-like structure was prepared by a simultaneous precipitation method followed by sintering of the sediment in H2 atmosphere at 800 °C. According to XRD data, the formation of single-phase solid solution Ni1-xMox took place for the samples with Mo content of 0.6–8.3 wt.%. Synthesized samples were studied in a process of the catalytic CVD of C2H4Cl2 at 550–700 °C. In situ kinetic studies of carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. An interaction of Ni-Mo alloys with C2H4Cl2 is accompanied by their rapid disintegration with formation of disperse active particles catalyzing the growth of carbon nanomaterials (CNM). The strong boosting effect of Mo on the catalytic performance of Ni was revealed. The maximum yield of CNM product (8.3 wt.% Mo, 600 °C, 120 min) was as high as 45 g/gM. The study on effect of the reaction temperature on the CNM yield allowed one to define an optimal temperature regime. The impact of Mo concentration upon the morphology, structural features and textural properties of the produced carbon fibers was investigated by means of SEM, TEM, Raman spectroscopy and low-temperature nitrogen adsorption. The role of chemisorbed chlorine species in a pulse-to-pulse regime of the segmented carbon filaments formation was discussed.

Environmental-friendly production of carbon fiber from isotropic hybrid pitches synthesized from waste biomass and polystyrene with ethylene bottom oil

Abstract In this study, spinnable isotropic pitches (IPs) were produced by pyrolytic oils of biomass and polystyrene (PS) with ethylene bottom oil (EBO or pyrolysis fuel oil: PFO) through bromination/dehydrobromination reaction. To develop spinnable pitches, four different tars were produced and hybrid pitches were synthesized using different PFO blending ratios and bromine amounts. Results showed that PFO improves spinnability and pitch yield considerably. Furthermore, pitches with the same softening point (S.P.) were produced from different precursors and spinning, stabilization and carbonization were performed to produce general-performance carbon fiber (CF). In order to explain the structure-property relationship of the products, mechanical, morphological and chemical characterization were done by TOF-MS, elemental analysis, 13C-NMR and SEM-EDX. Thus, a comparison between the characteristics of CFs was made disregarding the S.P.s and more insight into the effect of EBO was gained. Mechanical properties of CFs found to be reasonable, considering typical tensile values of IP-based CFs.

Catalytic synthesis of segmented carbon filaments via decomposition of chlorinated hydrocarbons on Ni-Pt alloys

Abstract A series of micro-disperse Ni1-xPtx alloys with the sponge-like structure was prepared by a simultaneous precipitation method with subsequent sintering of the sediment in H2 atmosphere at 800 °C. The formation of single-phase solid solution Ni1-xPtx was confirmed by powder XRD analysis for entire range of Pt concentrations (1.3–75.9 wt.%). The synthesized samples were studied in a process of catalytic decomposition of C2H4Cl2 at 600 °C. In situ kinetic studies of the carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. Interaction of Ni-Pt alloys with reaction mixture is characterized by an induction period (18–32 min) followed by rapid disintegration of the bulk alloys with intensive growth of carbon fibers. The stage of the induction period was explored in detail by means of XRD and SEM techniques. According to XRD data, the interaction of Ni-Pt alloys with C2H4Cl2 vapors is accompanied by formation of Ni1-xPtxCδ interstitial solution due to entry of carbon into the crystal lattice of the alloy. The effect of Pt addition on catalytic activity of Ni in CCVD process was also studied. It was found that the yield of carbon product depends extremely on Pt concentration with a maximum at CPt =4.3 wt.% (26 g/gNi for 120 min). The impact of Pt concentration upon morphology and structural features of the produced carbon fibers was investigated by SEM and TEM techniques.

Clean and low-cost synthesis of high purity beta-silicon carbide with carbon fiber production residual and a sandstone

Abstract The U.S. Department of Energy has initiated conversion of coal to solid materials, which can improve the coal-derived high-value product chain and decrease coal utilization related carbon dioxide emission. An integrated coal utilization technology was developed to respond to Department of Energy's call, which is extracting the molecules with desired molecular weight and structure in coal for carbon fiber production, then using carbon-rich residual from carbon fiber precursor extraction as carbon source to produce beta-silicon carbide. For the first time beta-silicon carbide is synthesized from carbon fiber production residual and a sandstone. The synthesized beta-silicon carbide was characterized with multiple analytical techniques. The product exhibits good properties with its purity, density, and Vickers hardness reach the requirements of commercial silicon carbide. Specifically, the purity of the beta-silicon carbide obtained with the two inexpensive raw materials under argon atmosphere at 1600 °C reaches as high as 98%. It is the first time that the furnace-MS system was applied to analyze the gaseous products in coal-based beta-silicon carbide synthesis process. Also, a possible synthesis mechanism was proposed and confirmed with experimental results. The research further analyzed the environmental impact and proposed the possibility that the liquid wastes/byproducts generated during raw material treatment process can be recycled and efficiently reused as coagulants or desiccants when the developed beta-silicon carbide synthesis process is applied in industry. This study provides a clean and low-cost approach for reusing waste residual from coal-based carbon fiber production and sandstone powder.

Rheology of Polyacrylonitrile/Lignin Blends in Ionic Liquids under Melt Spinning Conditions.

Lignin, while economically and environmentally beneficial, has had limited success in use in reinforcing carbon fibers due to harmful chemicals used in biomass pretreatment along with the limited physical interactions between lignin and polyacrylonitrile (PAN) during the spinning process. The focus of this study is to use lignin obtained from chemical-free oxidative biomass pretreatment (WEx) for blending with PAN at melt spinning conditions to produce carbon fiber precursors. In this study, the dynamic rheology of blending PAN with biorefinery lignin obtained from the WEx process is investigated with the addition of 1-butyl-3-methylimidazolium chloride as a plasticizer to address the current barriers of developing PAN/lignin carbon fiber precursors in the melt-spinning process. Lignin was esterified using butyric anhydride to reduce its hydrophilicity and to enhance its interactions with PAN. The studies indicate that butyration of the lignin (BL) increased non-Newtonian behavior and decreased thermo-reversibility of blends. The slope of the Han plot was found to be around 1.47 for PAN at 150 °C and decreased with increasing lignin concentrations as well as temperature. However, these blends were found to have higher elasticity and solution yield stress (47.6 Pa at 20%wt BL and 190 °C) when compared to pure PAN (5.8 Pa at 190 °C). The results from this study are significant for understanding lignin–PAN interactions during melt spinning for lower-cost carbon fibers.

Cleaner conversion of bamboo into carbon fibre with favourable physicochemical and capacitive properties via microwave pyrolysis combining with solvent extraction and chemical impregnation

Bamboo was converted into carbon fibre using a novel approach combining microwave pyrolysis, solvent extraction, and chemical impregnation. The employment of solvent extraction and chemical impregnation transformed natural bamboo into bamboo fibre with yield of 64 wt% that comprised of 87 wt% cellulose, 4 wt% lignin and 9 wt% hemicellulose deemed desirable for conversion into carbon fibre. The subsequent use of microwave pyrolysis transformed the bamboo fibre to form carbon fibre; the effects of microwave irradiation time and microwave power (two key process parameters) on properties of carbon fibre were investigated. Microwave pyrolysis provides a rapid heating rate (30 °C/min) with relatively shorter process time (20 min) compared to that performed by conventional pyrolysis method, thus leading to a relatively lower electric consumption and providing a potentially cost-saving and energy-efficient approach to produce carbon fibre. The production and properties of carbon fibre produced were affected by irradiation time and microwave power. The carbon fibre obtained was detected to have high fixed carbon (80 wt%), carbon element (87%), high BET surface area (475 m2/g) and fibres in small diameter (≤1 μm). It also shows desirable features comprising low content of moisture (<6 wt%), inorganic elements of Na, K, S, Mg (≤5%) and ash (1 wt%), allowing the carbon fibre to have more active sites and making it a cleaner product rather than polluting the environment whereas a high ash content could lead to undesired catalytic reactions and emission of potentially hazardous metallic components present in the ash. Combined with the detection of positive capacitive behaviour, the carbon fibre shows great potential to be used as an electrode for energy storage application. The results disclose that microwave pyrolysis combining with solvent extraction and chemical impregnation can be a cleaner approach to transform bamboo into carbon fibre with favourable physicochemical and capacitive properties.

Automatic Virtual Metrology for Carbon Fiber Manufacturing

Carbon fiber is currently one of the most popular composite materials in the world, with its wide applications ranging from bikes to space shuttles. However, there is no comprehensive method for the total quality inspection of carbon fiber products so far due to its feature of continuous production and destructive examination of quality inspection. Through years of development, the Automatic Virtual Metrology (AVM) technology has been applied to various industries to turn the offline sampling inspection with metrology delay into online and real-time total inspection. With AVM, every workpiece of the carbon fiber products can be examined to ensure total quality inspection. The biggest issue of continuous production is that it can neither accurately define each unit nor label on the products. To solve this problem, a production data traceback (PDT) mechanism is proposed in this letter. The PDT mechanism can provide a virtual label to each unit for referring back to the process parameters of the production. With PDT, the process data of each workpiece of a complete spin can be acquired so as to accomplish the work-in-process (WIP) tracking requirement of applying AVM. Also, the Advanced Manufacturing Cloud of Things (AMCoT) platform is adopted in this letter to fulfill all the smart manufacturing requirements for achieving the goal of zero defects of carbon fiber manufacturing.

A multi-objective Gaussian process approach for optimization and prediction of carbonization process in carbon fiber production under uncertainty

During composite fiber production, carbon fibers are normally derived from polyacrylonitrile precursor. Carbonization, as a key step of this process, is significantly energy-consuming and costly, owing to its high temperature requirement. A cost-effective approach to optimize energy consumption during the carbonization is implementing predictive modeling techniques. In this article, a Gaussian process approach has been developed to predict the mechanical properties of carbon fibers in the presence of manufacturing uncertainties. The model is also utilized to optimize the fiber mechanical properties under a minimum energy consumption criterion and a range of process constraints. Finally, as the Young’s modulus and ultimate tensile strength of the fibers did not show an evident correlation, a multi-objective optimization approach was introduced to acquire the overall optimum condition of the process parameters. To estimate the trade-off between these material properties, the standard as well as an adaptive weighted sum method were applied. Results were summarized as design chart for potential applications by manufacturing process designers.

Algae to sustainably produce carbon fiber and simultaneously take CO2 out of the atmosphere

Carbon fiber composite technology is a wonderful engineering tool for lowering the weight of vehicles and reducing their fuel consumption. It would be a perfectly green alternative to steel and aluminum if it were not for the fact that producing carbon fiber requires fossil materials and a lot of energy. A breakthrough technology from the Technical University of Munich in Germany promises to turn that on its head. The method not only makes it possible to produce carbon fiber without any fossil materials, it even takes CO2 out of the atmosphere instead of emitting it. The key to the technology: algae and direct solar power.