Carbon Fiber Precursor Research Articles

Synthesis and thermal behavior of acrylonitrile/guanidine crotonate copolymer for carbon fiber precursor

AbstractThe thermal oxidation stabilization of polyacrylonitrile (PAN) copolymer is a highly exothermic process. It significantly impacts the quality of the finished PAN‐based carbon fiber, which is often addressed by adding appropriate comonomers. This paper synthesized guanidine crotonate (GCA) as a comonomer and copolymerized with acrylonitrile (AN) to prepare P(AN‐GCA). DSC analysis revealed that when compared to PAN and P(AN‐CA) copolymers, the initial exothermic temperature, maximum exothermic heat flux, and heat flux of P(AN‐GCA) copolymer were greatly reduced. FT‐IR spectroscopy showed that the degree of pre‐oxidation increased with the increasing comonomer GCA content, indicating that the addition of comonomer GCA could promote PAN pre‐oxidation cyclization and improve the copolymer's degree of pre‐oxidation. The activation energies of PAN and P(AN‐GCA) were 160 and 126 KJ/mol, respectively. It was shown that the addition of GCA could effectively reduce the activation energy of the cyclization reaction of the polymer while simultaneously promoting it. TGA analysis shows that the introduction of GCA improves the copolymer's thermal stability, and the yield at 800°C is more than 54%, which is at least 19% higher than PAN homopolymer. P(AN‐GCA) has the potential to be carbon fiber precursor.

Structural reconstruction of lignin by mild and efficient dissolution: A strategy for the fabrication of mechanically strong carbon fiber precursors

Structural reconstruction of lignin by mild and efficient dissolution: A strategy for the fabrication of mechanically strong carbon fiber precursors

Heterogeneous microstructure of γ-irradiated pre-oxidized PAN fiber revealed by microfocus SR-SAXS reconstruction and molecular simulation.

The microstructure plays a crucial role in the manufacturing and application of polyacrylonitrile fibers, which serve as precursors for carbon fibers. Synchrotron radiation small angle x-ray scattering (SR-SAXS) is a non-destructive and precise technique for analyzing fiber structures. This study employed one-dimensional SR-SAXS mapping to extract key structural parameters such as periodicity, lamellae thickness, and the extent of amorphous regions, as well as the directional orientation in γ-irradiated, pre-oxidized polyacrylonitrile fibers. The analysis revealed a three-layered structure comprising a surface skin, a transitional layer, and a central core. Notably, the lamellar thickness exhibits a "U"-shaped distribution, while the long-period structures, amorphous regions, and orientational properties demonstrate a "wave-like" pattern. Within this structure, the skin exhibits a higher level of orientation, with the orientation decreasing progressively from the skin toward the core layer. The structure of the layered crystal was further corroborated by the morphological analysis. In addition, molecular simulations were performed to propose the mechanisms underlying the formation of this layered structure. This comprehensive investigation using SR-SAXS and one-dimensional mapping provides detailed insights into the microstructural and morphological characteristics of polyacrylonitrile fibers, which can inform future advancements in material processing and refinement techniques for the production of advanced fibers.

Effect of acid soak treatment of the precursor on the structure and properties of polypropylene-based carbon fibers

Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment.

Synthesis, Activation, and Characterization of Carbon Fiber Precursor Derived from Jute Fiber.

Activated carbon (AC) fiber is a carbonaceous material with a porous structure that has a tremendous scope of application in different fields. Conventionally, AC is derived from fossil fuel-based raw materials like polyacrylonitrile (PAN) and pitch. In this work, AC was synthesized from eco-friendly, renewable, and ubiquitous jute fiber. Systematically, the jute fiber was washed and pretreated with NaOH. Raw jute and NaOH-treated jute were carbonized/pyrolyzed at 500 °C for 1 h in presence of N2 gas. The carbonized carbon was activated with H3PO4 and KOH and again pyrolyzed at 650 °C for 1.5 h maintaining the inert condition. The different features of activated carbons were characterized with field emission-scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis. The average yield of carbonized and activated carbons was recorded at 19 and 13.8%, respectively. The scanning electron microscopic images confirmed a honeycomb-like porous structure. It was observed that KOH-activated carbon exhibited a more porous structure than the H3PO4-activated carbons. The average pore diameter of activated carbons was noted to be 1.3 μm. The pore density was higher in case of KOH-activated carbons accounting for 2.15 pore/μm. The EDX analysis showed that H3PO4-activated carbons had more than 90% carbon atoms indicating a significant carbon content. The TEM images revealed that AC particles were in the nanoscale range. The average particle sizes of H3PO4-activated carbon and KOH-activated carbon were 36.38 and 32.8 nm, respectively. The XRD study demonstrated the highly disordered and low level of crystallinity of AC. It was detected that the AC showed much higher thermal resistance than the jute fiber. The H3PO4-activated carbon obtained from NaOH-treated jute remained at 84% even after 500 °C. A higher thermal resistance was achieved with H3PO4-activated carbon since it contains 0.56% phosphorus, which was confirmed by EDX investigation. It was found that a higher carbon yield was obtained from NaOH-treated jute. The porous structure of the material showed that it could be used as an adsorbent. Due to its high thermal stability, it is recommended for flame retardants and heat insulation applications as well.

Fabrication of UV crosslinked polyethylene fiber for carbon fiber precursors

Fabrication of UV crosslinked polyethylene fiber for carbon fiber precursors

Structure and Properties of Thermally Stabilized and Ecologically Friendly Organic Cotton Fibers as a New Activated Carbon Fiber Precursor

Organic cotton precursor yarn was impregnated in an aqueous solution consisting of diammonium hydrogen phosphate (DAP), boric acid (BA), and urea (U) mixtures before the thermal stabilization stage and then subjected to heat treatments in an air environment at 245 °C. The effect of chemical pretreatment on organic cotton yarn was examined using methods such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. The XRD analysis revealed a gradual decrease in the crystalline structure, attributed to the disruption of intermolecular hydrogen bonds. DSC and TGA measurements showed an improved thermal stability due to the formation of pre-graphitic structures with aromatic entities at higher temperatures. For samples chemically impregnated and then stabilized, the char yield values increased from 25% to 68% at 500 °C and 23% to 53% at 1000 °C. Analysis of IR spectra indicated a gradual reduction in both intermolecular and intramolecular hydrogen bonds associated with dehydration and dehydrogenation reactions. The IR spectra also confirmed a decrease in crystallinity with increasing oxidation time, which is consistent with the findings from X-ray diffraction. In addition, the IR spectra showed the presence of C = C bonds, indicating the formation of a crosslinked ladder-like structure. The results showed that DAP-BA-U integration increased the thermal stability of organic cotton fibers and the obtained samples were ready for the next stage, carbonization.Graphical

Narrow polydispersity P(AN-MA) copolymers synthesized in continuous flow as potential carbon fiber precursors

In this work, poly (acrylonitrile-methyl acrylate) [P(AN-MA)] copolymers with controllable molecular weights and narrow polydispersity were successfully synthesized in continuous flow without pre-deoxygenation. A dual-reactor method was designed to prepared P(AN-MA) with higher molecular weight and achieve a high yield from 62.57 % to 70.16 %. To facilitate industrial production of P(AN-MA), pre-mixing stage was added in continuous flow for replacing the ultrasonic mixing process. The characteristic mixing time is 27.80 min and the length of Polyfluoroalkoxy (PFA) tube exceeds 74.625 m for thoroughly mixing. Higher molecular weight P(AN-MA) copolymers possess poorer preoxidation properties such as higher initiation temperature, more concentrated heat release and larger activation energy of cyclization reaction as well as lower extent of stabilization and poorer thermal stability against high-temperature treatment. Moreover, 192 g P(AN-MA) was continuously prepared by the dual-reactor method for 105 min without suffering from notable pressure increase.

Prospect of Controlled Autoxidation to Produce High-Value Products from the Low-Value Petroleum Fractions.

Substantial amounts of low-value light petroleum fractions and low-value heavy petroleum fractions, such as light naphtha, HVGO, and vacuum residue, are generated during the upgrading and refining of conventional and unconventional petroleum resources. The oil industry emphasizes economic diversification, aiming to produce high-value products from these low petroleum fractions through cost-effective and sustainable methods. Controlled autoxidation (oxidation with air) has the potential to produce industrially important oxygenates, including alcohols, and ketones, from the low-value light petroleum fractions. The produced alcohols can also be converted to olefin through catalytic dehydration. Following controlled autoxidation, the low-value heavy petroleum fractions can be utilized to produce value-added products, including carbon fiber precursors. It would reduce the production cost of a highly demandable product, carbon fiber. This review highlights the prospect of developing an alternative, sustainable, and economic method to produce value-added products from the low-value petroleum fractions following a controlled autoxidation approach.

Investigation of controlled autoxidation of HVGO to produce carbon fibres precursors: Role of oxygen availability and mixing

Carbon fibre is an ultra-light, strong, and durable material that has growing demand in different industries. About 95 % of currently produced carbon fibre is PAN-based which is expensive. Considering the expense and accessibility, heavy vacuum gas oil (HVGO) shows significant promise. However, it necessitates appropriate pre-treatment to generate carbon fibre precursors. The present study examined the influence of oxygen availability and mixing on controlled autoxidation (oxidation with air) in order to establish a cost-effective and efficient pre-treatment technique for assessing the feasibility of generating carbon fibre precursors from the low-value heavy petroleum fraction HVGO. Experiments were performed while maintaining temperature (130–260 ℃), time (4–24 hours), and oxygen partial pressure (N2/air) maintaining bubbling with mixing, and also blowing without mixing. Blowing without mixing at 200 ℃ for 24 h showed the highest viscosity of 7959 cP (measured at 25 ℃), and HVGO heated at 240 ℃ in 8 h in the presence N2 resulted in a maximum 26 % increase in aromaticity. It was also noticed that there was an improvement in softening point (maximum 5.4 times), volatility, and heavy products, which are crucial properties of a carbon fibre precursor. Understanding from the current research can also be applied in the area of asphalt hardening, weathering, fouling, fuel transportation and storage stability, and sludge formation.

Detailed Characterization of Vitrinite-Rich Subbituminous and Bituminous Coals for Utilization in Carbon Fiber Precursor Production

Detailed Characterization of Vitrinite-Rich Subbituminous and Bituminous Coals for Utilization in Carbon Fiber Precursor Production

An Evaluation of the Beneficial Effects of Polyamide 6's Thermal Stabilization by Ferric Chloride Complexation as a Novel Carbon Fiber Precursor

This study investigated the impact of stabilization time on pretreated polyamide 6 (PA6) fibers using various analytical techniques, including thermal analysis (TGA and DSC), infrared (IR) spectroscopy, X-ray diffraction (XRD), tensile testing, and density measurements. The two-step atmospheric air-based stabilization process for pretreated PA6 multifilament bundles involved initial thermal stabilization at 170 °C in an air atmosphere after ferric chloride impregnation, followed by a second step of thermal stabilization at 245 °C. Ferric chloride impregnation followed by thermal stabilization in an air atmosphere resulted in crucial structural transformations. The density values of the samples increased following thermal stabilization, accompanied by a decrease in tensile values. Ferric chloride pretreated and thermally stabilized PA6 fibers were found to be fully stabilized after 120 min of stabilization before the carbonization stage. The findings obtained from the DSC, XRD, and IR spectroscopy methods indicated the occurrence of disordering phases due to the scission of hydrogen bonds. The TGA findings showed significant increases in carbon yield percentages at 500 °C and 850 °C, reaching 71.4% and 63.5%, respectively, for the sample heat treated at 245 °C for 120 min. The addition of ferric chloride is expected to potentially reduce processing costs for final carbon fiber production by decreasing the time required for the thermal stabilization of PA6.

Highly strong carbon fibers through synergistic carbonization process of sulfonated poly(p-phenylene sulfide) and carbon nanotube

This paper presents the fabrication and characterization of high-performance carbon nanotube-polyphenylene sulfide (CNT-PPS) composite fibers. The study begins by dissolving PPS in chlorosulfonic acid (CSA) to create dopes suitable for wet-spinning, enabling the formation of CNT-PPS composite fibers. The presence of PPS, known for its low solubility and high crystallinity, leads to improved mechanical properties and thermal stability after carbonization. The structural evolution of the fibers during heat treatment is examined. The results show that the fibers' tensile strength and modulus increase significantly after carbonization, with the highest tensile strength (6.04 ± 0.50 GPa) achieved by the fiber containing 30 wt% of PPS heat-treated at 1400 °C and the highest tensile modulus (619 ± 44 GPa) achieved by the fiber containing 10 wt% of PPS heat-treated at 2500 °C. The mechanism of radical coupling between CNTs and PPS during de-sulfonation is proposed as a key factor contributing to the enhanced mechanical properties. The study also highlights the benefits of using PPS as a carbon fiber precursor, eliminating the need for costly and time-consuming stabilization processes. Overall, this research offers a novel strategy for producing high-performance and cost-effective carbon nanotube-based carbon fibers with applications in various industries.

Accelerated thermostabilization through electron-beam irradiation for the preparation of cellulose-derived carbon fibers

The potential of biobased materials like regenerated celluloses as precursors for carbon fibers (CFs) is long known. However, owing to an intrinsic two pathway pyrolysis mechanism of cellulose its carbonization is accompanied with side reactions under generation of volatiles. In practice, this leads to a reduced char yield, results in inferior mechanical properties of the CFs, and requires time-consuming thermostabilization procedures or wet-chemical pretreatments during production. Thus, their market share currently remains low. In ambitions to circumvent these issues, the potential of electron beam irradiation (EBI) as a dry chemical pretreatment for cellulosic CFs was investigated in this study. The conducted chemical analyses showed that high radiation dosages (2 MGy) lead to a strong depolymerization of the cellulose chains down to oligomers, while the fibrous macrostructure was preserved. Minor oxidation reactions were also evident. Thorough thermostabilization experiments under air in the temperature range from 100 °C to 250 °C revealed that reactions caused by EBI treatment alone were insufficient to increase the char yield. Only when the EBI treated precursor fibers are subjected to heating between 200 and 250 °C the char yield increased significantly to 34.4 % compared to 12.1 % for the untreated fiber. Furthermore, the EBI treatment strongly accelerated the reactions during thermostabilization allowing to collect CFs at heating rates of 2 °C/min compared to 0.5 °C/min needed for pristine fibers. Additionally, cellulose-lignin composite fibers were subjected to EBI treatment, proving that this strategy can also be applied to these emerging biobased CF precursors.

Techno-economic assessment of atmospheric CO2-based carbon fibre production enabling negative emissions

The fight against global warming requires novel approaches for the defossilisation of industrial processes, and the limitation of global warming requires options for negative carbon dioxide (CO2) emissions. The production of carbon fibre (CF) is an energy-intensive chain of processes which cause CO2 emissions. Having in mind the high market growth for CF composite materials, CF production might stand against the fight against global warming. CF also offers a huge mitigation opportunity, as CF contain up to 95–98wt% of pure carbon. This study investigates possible ways to link CF production to atmospheric CO2, enabling negative CO2 emissions through CF manufacturing. Production value chains for CF based on poly(acrylonitrile) (PAN) and pitch, the two most important CF precursor materials, are developed and analysed regarding their energy and mass balances. The PAN value chain is further assessed regarding a first economic estimation of CF production cost with atmospheric CO2 as carbon source. The results show that production costs per ton CO2 removed might be unattractive at 2949 €/tCO2 in 2050. However, from a CF perspective, production cost of 10.3 €/kgCF in 2050 might enable a business case for electricity-based CF production from atmospheric CO2 in the future. Each ton of CF produced can store about 3.5 tCO2 due to a very high carbon share in the final product. With an increasing market for CF, a total negative emission potential of at least 0.7 GtCO2 per year can be enabled by 2050. Further research opportunities are discussed.

Fabrication of a three-dimensional micro/nanocarbon structure with sub-10 nm carbon fiber arrays based on the nanoforming and pyrolysis of polyacrylonitrile-based jet fibers

To produce a three-dimensional micro/nanocarbon structure, a manufacturing design technique for sub-10 nm carbon fiber arrays on three-dimensional carbon micropillars has been developed; the method involves initiating electrostatic jetting, forming submicron-to-nanoscale PAN-based fibers, and maximizing the shrinkage from polyacrylonitrile (PAN)-based fibers to carbon fibers. Nanoforming and nanodepositing methods for polyacrylonitrile-based jet fibers as precursors of carbon fibers are proposed for the processing design of electrostatic jet initiation and for the forming design of submicron-to-nanoscale PAN-based fibers by establishing and analyzing mathematical models that include the diameter and tensile stress values of jet fibers and the electric field intensity values on the surfaces of carbon micropillars. In accordance with these methods, an array of jet fibers with diameters of ~80 nm is experimentally formed based on the thinning of the electrospinning fluid on top of a dispensing needle, the poking of drum into an electrospinning droplet, and the controlling of the needle–drum distance. When converting thin PAN-based jet fibers to carbon fibers, a pyrolysis method consisting of the suspension of jet nanofibers between carbon micropillars, the bond between the fibers and the surface of the carbon micropillar, and the control of micropillar spacing, stabilization temperature, and carbonation rate is presented to maximize the shrinkage from PAN-based fibers to carbon fibers and to form sub-10 nm carbon fiber arrays between three-dimensional carbon micropillars. The manufacturing design of a three-dimensional micro/nanocarbon structure can produce thin PAN-based jet nanofibers and nanofiber arrays aligned on micropillar surfaces, obtain shrinkage levels reaching 96% and incorporate sub-10 nm carbon fibers into three-dimensional carbon micropillars; these actions provide new research opportunities for correlated three-dimensional micro/nanocarbon structures that have not previously been technically possible.

Numerical modeling of the carbonization of polyimide fibers in a cylindrical furnace

Carbon fiber is widely used as a reinforcing material in polymer composite such as carbon fiber reinforced plastic (CFRP) due to its high specific strength, elastic modulus and lightweight. The majority of the industrial carbon fiber is produced from synthetic precursor polymer such as polyacrylonitrile (PAN), pitch and polyimide. While relatively many studies have been published for the carbonization of PAN, little studies have been found on the heat transfer during carbonization of polyimide precursors. In this study, we numerically analyzed the carbonization process of a polyimide (PI) precursor for carbon fibers in a lab-scale cylindrical furnace. Gas flow, temperature distribution and concentration profiles including the off-gases from the precursor fibers were included in the analyses. First, we established mathematical models for the off-gases behavior from the precursor fibers. The models were incorporated into computational fluid dynamics in order to find behavior of the mixture gas of the working nitrogen gas and the off-gases. And then, numerical simulation results using the model were obtained and compared to the experimental results to verify the model. Finally, we evaluated the application scalability of the established numerical model through changes in wall temperature and precursor fiber moving speed. The results showed that the model can be used to study the PI carbonization process in the industrial size carbonization furnace.

The Production of Ultra-Thin Polyethylene-Based Carbon Fibers out of an “Islands-in-the-Sea” (INS) Precursor

Carbon fibers (CF) and their composites (CC) are one of the world’s most promising and avant-garde high-performance materials, as they combine excellent mechanical characteristics with high weight reduction potential. Polyethylene (PE) is the perfect alternative precursor for CF as it combines widespread availability, low cost, high carbon content, and, most importantly, precursor fibers that can be produced via melt-spinning. PE-based CF production involves a challenging and time-consuming diffusion-limited chemical stabilization step. The work presented in this article tackles the challenge of reducing the chemical stabilization process time by converting a bicomponent island-in-the-sea fiber, consisting of PA6 as sea matrix and HDPE as island material, into an ultra-thin PE-precursor fiber. The produced precursor fiber is then successfully converted into an ultra-thin PE-based CF through sulfonation and subsequent carbonization in a continuous set-up. The resulting CF has a smooth surface with no observable surface defects and a filament diameter of around 3 µm. The successful conversion to ultra-thin CF is shown in both batch and continuous processes. Additionally, a reduction in sulfonation reaction time from 4 h to 3 h is achieved.

Interdependent factors influencing the carbon yield, structure, and CO_{2} adsorption capacity of lignocellulose-derived carbon fibers using multiple linear regression

Cellulose has experienced a renaissance as a precursor for carbon fibers (CFs). However, cellulose possesses intrinsic challenges as precursor substrate such as typically low carbon yield. This study examines the interplay of strategies to increase the carbonization yield of (ligno-) cellulosic fibers manufactured via a coagulation process. Using Design of Experiments, this article assesses the individual and combined effects of diammonium hydrogen phosphate (DAP), lignin, and CO_{2} activation on the carbonization yield and properties of cellulose-based carbon fibers. Synergistic effects are identified using the response surface methodology. This paper evidences that DAP and lignin could affect cellulose pyrolysis positively in terms of carbonization yield. Nevertheless, DAP and lignin do not have an additive effect on increasing the yield. In fact, combined DAP and lignin can affect negatively the carbonization yield within a certain composition range. Further, the thermogravimetric CO_{2} adsorption of the respective CFs was measured, showing relatively high values (ca. 2 mmol/g) at unsaturated pressure conditions. The CFs were microporous materials with potential applications in gas separation membranes and CO_{2} storage systems.Graphical abstract

Terpolymers of acrylonitrile, methyl acrylate, and 2‐acrylamido‐2‐methylpropane sulfonic acid for carbon fiber precursor: Effect of comonomers on the thermal stabilization of polyacrylonitrile copolymers

AbstractPolyacrylonitrile (PAN) copolymers are important precursors for the preparation of high‐performance PAN‐based carbon fibers. In this study, different ratios of P(AN‐co‐AMPS) and P(AN‐co‐MA‐co‐AMPS) were prepared by solution polymerization. The compositional structure, thermal, and crystallization properties of P(AN‐co‐AMPS) and P(AN‐co‐MA‐co‐AMPS) were characterized. The results show that an increase in the AMPS feeding ratio is beneficial for improving the thermal stability and crystallization ability of the PAN copolymer; however, it also reduces the molecular weight of the copolymer and increases the cyclization exothermic peak temperature, which is not conducive to the preparation of high‐performance carbon fibers. This problem is avoided in P(AN‐co‐MA‐co‐AMPS), which maintains its high thermal stability and crystallization properties when appropriate amounts of MA and AMPS are introduced, and P(AN‐co‐MA‐co‐AMPS) has smoother cyclization exothermic rates, lower onset exothermic temperatures and lower peak exothermic temperatures. The structural changes of PAN, P(AN‐co‐MA), and P(AN‐co‐MA‐co‐AMPS) during thermal stabilization were investigated in detail using Fourier‐transform infrared spectroscopy and it was found that P(AN‐co‐MA‐co‐AMPS) formed more stable structures at lower temperatures. Furthermore, when the AN:MA:AMPS mass ratio is 97.5:1.5:1, P(AN‐co‐MA‐co‐AMPS) has the best overall performance. Our results suggest that the P(AN‐co‐MA‐co‐AMPS) has potential as a precursor for carbon fibers.