Spinnable Pitch Research Articles

Preparation of a high-performance synthetic pitch from aromatic hydrocarbons containing N/Cl

The preparation of a synthetic pitch from aromatic monomers could easily regulate structure orientation at the molecular level, which would be useful in fabrication. An isotropic synthetic pitch was prepared by a chlorine- and/or nitrogen-induced substitution polymerization reaction method using aromatic hydrocarbon precursors containing Cl and N, which for this study were chloromethyl naphthalene and quinoline. This method was verified by investigating the structural changes under different synthesis conditions, and the synthesis mechanism induced by aromatics containing Cl was also probed. The result shows that the pyridinic N in quinoline contains a lone pair of electrons, and is an effective active site to induce the polymerization reaction by coupling with aromatic hydrocarbons containing Cl. The reaction between such free radicals causes strong homopolymerization and oligomerization. A higher reaction temperature and longer reaction time significantly increased the degree of polymerization and thus increased the softening point of the pitch. A linear molecular structure was formed by the Cl substitution reaction, which produced a highly spinnable pitch with a softening point of 258.6 °C, and carbon fibers with a tensile strength of 1 163.82 MPa were obtained. This study provides a relatively simple and safe method for the preparation of high-quality spinnable pitch.

Insight into the structural variation mechanism of highly spinnable isotropic pitch prepared by halogenated model aromatic compounds

This study developed a novel method for synthesis highly spinnable pitch through thermal polymerization of halogenated polycyclic aromatic hydrocarbons (PAH-X) and anthracene oil (AO). The characteristics, average molecular model, and polymerization mechanism of the as-prepared pitches were systematically elucidated. Results show that the thermal cleavage of C-X bonds of the PAHs-X could generate large number of free radicals that greatly facilitate the cross-linking reaction of the active fragments. Namely, the formation of benzyl radicals with high reactivity of the raw materials made it possible to synthesize pitches at lower temperature. The softening point of the as-prepared pitches showed a decreasing trend with increasing of AO proportion due to the abundant carbon content and lower reactivity of AO. Higher temperature could elevate the polymerization activity of aromatic fragments, thus significantly promoted the formation of macromolecular aromatic structures to obtain the spinnable pitch with suitable softening point. The average models validated by calculating the NMR spectra was successfully constructed to demonstrate the condensation degree, which was found be conducive to probe the spinnability of the pitches. Further, the average molecular models could well describe the correlation of the molecular structure, spinnability of pitches, as well as the mechanical properties of carbon fiber.

Evolution of the Composition and Melting Behavior of Spinnable Pitch during Incubation.

The physical and chemical properties of spinnable pitch showed a huge impact on the performance of resultant pitch carbon fiber even if its physical and chemical properties were slightly changed. Various polycyclic aromatic compounds and abundant free radicals existed in spinnable pitch, and there are many interactions among molecules and free radicals. The molecular structure and composition of spinnable pitch were investigated during incubation, and the effect of molecular evaluation on rheological properties of spinnable pitch was illustrated using various characterization methods in this work. It indicated that n-hexane soluble fraction mainly occurred condensation or cleavage, and a small number of heavy components were generated after a long period. The fraction of n-hexane insoluble/toluene soluble underwent molecular condensation and cross-linking in the presence of oxygen-containing radicals and aromatic hydrocarbon radicals, while toluene insoluble/tetrahydrofuran soluble fraction tended to change in large molecules of polycyclic aromatic hydrocarbons. Lastly, tetrahydrofuran insoluble fraction was condensed due to its high aromaticity during the incubation process, and the content of aromatic carbon increased. These changes of composition and structure of spinnable pitch led to its softening point, increase in viscosity and flow activation energy, and deterioration of the rheological property.

Molecular growth from coal-based asphaltenes to spinnable pitch

The chemical composition of spinnable pitch determined the performance of resultant carbon fiber. Three spinnable pitches were prepared from asphaltenes by a modified air-blowing method and their component and structural differences were comparatively investigated using MALDI-TOF and Q-TOF MS. The three spinnable pitches had insignificant changes in elemental compositions, while the molecular species and their relative content varied significantly, and the molecular weight growth of spinnable pitches was consistent with the 24/50 rule of aromatic annelation. Dominant compounds in the molecular weight range of 250–600 Da showed a clear growth tendency via alternate additions of C4H2 and C2, and species of larger molecular weight grew mainly in conjunction with C2. As an excellent precursor for pitch-based carbon fiber, spinnable pitch derived from asphaltenes should have a uniform molecular weight distribution and high number-average molecular weight (1672.6 Da), good thermal stability, high polycondensation degree and aromatic hydrocarbons with the short or few chains in its light fraction. This work systematically analyzed spinnable pitch composition and shed light on the controllable synthesis of pitch-based carbon fiber.

Preparation of Isotropic Carbon Fibers from Kerosene-Purified Coal Tar Pitch by Co-Carbonization with Pyrolysis Fuel Oil.

An inexpensive and general-purpose carbon fiber was prepared using coal tar pitch. In contrast to the solvent extraction process employing expensive solvents, a low-cost centrifugal separation method facilitated the reduction of loss due to the pitch purification and an overall yield increase. The coal tar pitch purified by centrifugation and subsequently co-carbonized with pyrolysis fuel oil improved in spinnability. Moreover, the resulting spinnable pitch had a softening point of 250 °C. The obtained carbon fibers were heat-treated at 1000 °C for 5 min, resulting in a tensile strength of approximately 1000 MPa and an average diameter of 9 μm. In this study, we present an effective method for obtaining low-cost general-purpose isotropic carbon fibers.

Study on structures and properties of isotropic pitches and carbon fibers from co-carbonization of aromatic-rich distillate oil and polyethylene glycol

Obtaining cost-competitive carbon fibers with excellent mechanical properties remains a great challenge. Here we report the co-carbonization of polyethylene glycol (PEG) and an aromatic-rich distillate oil (HCT0-RF) to prepare isotropic pitches that have superior spinnability for the production of carbon fibers. Among all of the carbon fiber productions, H-P10-CFs exhibited the best tensile strength of 1050 MPa and elongation of 2.5 %, respectively, at the breaking point. We reason that the addition of PEG into HCTO-RF can effectively increase the yield of isotropic pitches, accompanied by restricting the appearance of the mesophase spheres. The amount of aliphatic carbon in spinnable pitches were observed to increase with the amount of PEG. Thus, the changes in molecular structure can improve the rheological properties of spinnable pitch and enhance the spinnability. In addition, the increase of aliphatic components can accelerate the oxidative reaction and promote the stabilization efficiency. Unfortunately, excessive aliphatic components would inevitably cause higher oxygen uptake content, which deteriorate the uniformity of the fiber structures during carbonization process. With the increase of PEG content, the tensile strength of these carbon fibers increased first and then decreased. The optimized PEG content should be in the range of 5–10 wt%. The PEG acted as the co-carbonization agent provides new perspective in the field of carbon fiber production.

A comprehensive investigation on the chemical structure character of spinnable pitch for improving and optimizing the oxidative stabilization of coal tar pitch-based fiber

Oxidative stabilization is the critical step to maintain the fibrous morphology of pitch fiber and affects mechanical properties of resultant carbon fiber, but the detailed oxidation mechanism is still unclear because of the complex polycyclic aromatic hydrocarbons composition in pitch fiber. In here, pitch fiber was obtained from coal tar pitch followed by air-blowing and spinning. The chemical structure character of corresponding fibers before and after oxidative stabilization at different temperatures (260–320 °C) and durations (2–12 h) were analyzed. The results indicated that aromatic nucleus in spinnable pitch was gradually increased, while aliphatic chains were gradually shorten with prolongation of air-blowing time. The spinnable pitch obtained by air-blowing at 330 °C for 4 h showed excellent spinning performance, and the as-spun pitch fiber displayed a higher oxidative stabilization efficiency because the lower oxygen content was introduced and more C-O-C groups were formed in the resultant oxidative stabilized pitch fiber. The obtained pitch-based carbon fiber, after carbonizing at 1000 °C, showed excellent mechanical properties with tensile strength of 1068.7 ± 100.0 MPa and Young's modulus of 52.5 ± 9.8 GPa. This work provided a facile approach to improve and optimize the oxidative stabilization efficiency for pitch carbon fiber preparation.

Preparation of isotropic spinnable pitch with high-spinnability by co-carbonization of coal tar pitch and bio-asphalt

Co-carbonization of coal tar pitch (CTP) with bio-asphalt (BA) was performed to prepare spinnable pitch with suitable softening point and excellent spinnability for general purpose carbon fiber. The co-carbonization mechanism and the correlation between spinnability and molecular structure of prepared pitch were clarified. BA produced from the pyrolysis of biomass is abundant of aliphatic units and oxygen-containing groups, leading to high reactivity during carbonization. The co-carbonization reactions mainly depend on the mutual cross-linking among CTP and BA molecules, which are principally triggered by active oxygen-containing groups of BA. The formed cross-linked macromolecules could further promote the polymerization degree of pitch molecules; thus, the spinnable pitch with suitable softening point could be obtained by simply thermal treatment of blended pitches at a relatively moderate condition (<350 °C). The properties of the pitch could be optimized by changing the blending ratio of CTP to BA. Moreover, the prepared carbon fibers demonstrated distinct features, especially surface profiles. It is expected to provide a new strategy for the preparation of isotropic spinnable pitch in a relatively simple approach.

Preparation and characterization of high-spinnability isotropic pitch from 1-methylnaphthalene-extracted low-rank coal by co-carbonization with petroleum residue

Coal extract produced by solvent extraction of low-rank coal is not suitable for spinning due to its high oxygen content. In order to effectively overcome this limitation, soft pitch was produced by co-carbonization of coal extract and petroleum residues. The decrease in oxygen content was confirmed by physical property analyses of the soft pitches blended at different mixing ratios. A bridge/hydroaromatic structure of the soft pitch was observed during the co-carbonization. The produced spinnable pitch had a high spinnability and a softening point of 230 °C. This spinnable pitch, prepared by solvent extraction of low-rank coal, showed excellent spinnability and was heat-treated at 800 °C for 5 min to produce isotropic carbon fibers having diameters of 7 μm and a tensile strength of 1189 MPa. Thus, the co-carbonization of coal extract and petroleum residue is an effective method for the production of inexpensive spinnable pitch for isotropic carbon-fiber manufacture.

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.

Effect of the oxygen content and the functionality of spinnable pitches derived from ethylene tar by distillation on the mechanical properties of carbon fibers

Effect of the oxygen content and the functionality of spinnable pitches derived from ethylene tar by distillation on the mechanical properties of carbon fibers

Controlling spinning pitch property by tetrahydrofuran-soluble fraction of coal tar pitch co-carbonization with petrolatum

Isotropic pitch-based carbon fiber was successfully prepared from tetrahydrofuran-soluble fraction of coal tar pitch co-carbonization with petrolatum by air-blowing. The effects of reaction temperature and time, amount of petrolatum added on the composition and spinning properties of resultant pitches were investigated. It indicated that petrolatum could effectively improve the softening point, aromaticity, hydrogen content and molecular weight of the resultant pitches by promoting cross-linking and dehydrogenation polymerization reactions at low air-blowing temperature. Moreover, more aliphatic and naphthenic structures had been introduced into resultant pitches as addition of petrolatum and also inhibited the generation of quinoline-insoluble particles. The obtained green fibers were facile to be stabilized and carbonized and the resultant carbon fibers showed fully isotropic and finer, uniform diameter with smooth surface and higher tensile strength of up to 0.92 GPa. It provided a facile chemical modification method for isotropic pitch-based carbon fiber production. Spinnable pitches and isotropic pitch-based carbon fiber with higher tensile strength prepared from CTP-THFS co-carbonization with petrolatum by air-blowing.

Preparation and characterization of spinnable pitch for general‐purpose carbon fiber from refined pitch

ABSTRACTFour types of spinnable pitches (MP‐N‐A, MP‐A, MP‐A‐H, and MP‐A‐N) for general‐purpose carbon fiber have been prepared under certain conditions with the refined pitch as the raw materials. Fourier transform infrared spectrum and solid‐state nuclear magnetic resonance spectra combined with curve‐fitting analysis have been used to characterize the average molecular structure (Iar, CH3/CH2, SAR, and SHFG) of spinnable pitches. Thermogravimetric analyses and polarizing microscope have been used to observe the thermal stability and the microstructure of spinnable pitches, respectively. The X‐ray diffraction combined with curve‐fitting analysis have showed that, the stacking heights (Lc) of these four kinds of spinnable pitches were 2.21, 1.78, 1.79, and 1.76 nm, respectively. The parallel layers (N) of each spinnable pitch were 7.30, 6.02, 6.06, and 5.97. What is more, the numbers of aromatic ring in each layer (n) were 17.03, 11.61, 11.75, and 11.41. Finally, the scanning electron microscopy has been used to characterize the surface morphology of carbon fibers which obtained by each spinnable pitches. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47880.

Chemical Modification of Asphaltene with SEBS as Precursor for Isotropic Pitch‐Based Carbon Fiber

AbstractA high yield spinnable pitch for isotropic pitch‐based carbon fiber was successfully prepared by air oxidation polycondensation of asphaltene with styrene‐ethylene‐butylene‐styrene. The effects of reaction temperature and time, added styrene‐ethylene‐butylene‐styrene amount on the composition and spinning properties of resultant pitches were investigated. The resultant pitch with a concentrated molecular weight distribution of 300–700 Da was prepared at 340 °C for 3 h under air blowing with 5% styrene‐ethylene‐butylene‐styrene, moreover, its more alkyl structure (mainly methylene), lower apparent viscosity above the softening point, and good spinnability endowed the resultant pitches more prone to oxygen cross‐linking during the stabilization process. The average tensile strength of resultant pitch‐based carbon fibers was over 800 MPa after carbonization at 1000 °C for 10 min. It provided a simple method to adjust the spinnable pitch for pitch‐based carbon fiber preparation.

Effect of the oxygen content and the functionality of spinnable pitches derived from ethylene tar by distillation on the mechanical properties of carbon fibers

Three basic pitches were prepared by the distillation of ethylene tar at 200, 250, or 300 °C for 3 h. Spinnable pitches were produced from them using air-blowing followed by heat treatment at 330°C for 4 h and are designated P200AT, P250AT and P300AT, respectively. These three pitches, and stabilized fibers and carbon fibers produced from them were characterized by TG-MS, FT-IR, 13C-NMR, XRD, SEM, solubility tests and elemental analysis. The components and oxidation reactivity of the basic pitches, and its influence on the oxygen functionality and microstructures of the spinnable pitches and mechanical properties of the resulting carbon fibers were investigated. Results showed that with increasing distillation temperature the aliphatic carbon content and n-hexane and toluene solubility of the basic pitches decreased, while their aromaticity and planarity increased, and the oxidation reactivity reached a maximum at 250 °C. Of the three spinnable pitches P250AT had the highest softening point, highest carbon yield, oxygen content, and C=O content and the highest toluene insoluble fraction. However, the oxygen uptake of P250AT pitch fibers during stabilization was the lowest among the three. This led to a reduction of gas release during carbonization, and therefore the highest carbon yield, the smallest number of defects, the highest tensile strength and the lowest Young's modulus of all the carbon fibers.

Improving Spinnability of Hyper-Coal Derived Spinnable Pitch through the Hydrogenation with 1,2,3,4-Tetrahydroquinoline

The proper hydrogenation of Hyper-coal (HPC) using 1,2,3,4-tetrahydroquinoline (THQ) was able to decrease the oxygen content and adjust the molecular structure of HPC for preparing the spinnable pitch with high softening point (SP). The spinnable pitch prepared from the THQ-soluble (QS) fraction of HPC as a precursor consisted of more naphthenic carbon groups than that prepared from the 1-methylnaphthalene (1-MN) soluble (MNS) fraction of HPC. The HPC-QS derived spinnable pitch showed excellent spinning performance even though the SP of 260 °C, and the tensile strength of the resultant carbon fiber was increased to 1350 MPa with a diameter around 8 µm under the only carbonization temperature of at 800 °C for 5 min.

Preparation of isotropic spinnable pitch and carbon fiber by the bromination–dehydrobromination of biotar and ethylene bottom oil mixture

An isotropic pitch which has a relatively high softening point and an excellent spinnability for general performance carbon fiber was successfully prepared through the low-temperature co-carbonization with ethylene bottom oil (EO). The special bromination and dehydrobromination reaction of the mixed biotar and EO was adapted at a relatively low temperature for minimizing the phase separation of the two raw materials. The optimized reaction conditions for bromination and dehydrobromination were the heat treatments at 110 °C for 1 h with 20 wt% of Br2 addition and at 320 °C for 3 h under N2 atmosphere, respectively. After removal of volatile matters by thin layer evaporation at 350 °C, the target spinnable isotropic pitch, which has a relatively softening point of 205 °C and excellent spinnability, was successfully obtained with high synthetic yield of 45 wt%. The carbon fiber fabricated using the obtained isotropic pitch precursor showed an enormous tensile strength of 1200 MPa by heat treatment alone at 800 °C for 5 min.

Pitch-based carbon fibers from coal tar or petroleum residue under the same processing condition

Spinnable pitches and carbon fibers were successfully prepared from petroleum or coal pyrolysis residues. After pyrolysis fuel oil (PFO), slurry oil, and coal tar were simply filtered to eliminate the solid impurities, the characteristics of the raw materials were evaluated by elemental analysis, 13C nuclear magnetic resonance spectrometer, matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF-MS), and so on. Spinnable pitches were prepared for melt-spinning carbon fiber through a simple distillation under strong nitrogen flow, and further vacuum distillation to obtain a high softening point. Carbon fibers were produced from the above pitches by single-hole melt spinning and additional heat treatment, for oxidization and carbonization. Even though spinnable pitches and carbon fibers were processed under the same conditions, the melt-spinning and properties of the carbon fiber were different depending on the raw materials. A fine carbon fiber could not be prepared from slurry oil, and the different diameter carbon fibers were produced from the PFO and coal tar pitch. These results seem to be closely correlated with the initial characteristics of the raw materials, under this simple processing condition.

Modification of Coal-Tar-Pitch and Carbon Fiber Properties by Polymer Additives

In order to use coal tar pitch (CTP) as a raw material for carbon fibers, it should have suitable properties such as a narrow range of softening point, suitable viscosity and uniform optical properties. In this study, raw CTP was modified by heat treatment with three types of polymer additives (PS, PET, and PVC) to make a spinnable pitch for carbon fibers. The yield, softening point, C/H ratio, insoluble yield, and meso-phase content of various modified CTPs with polymer additives were analyzed by changing the type of polymer additive and the heat treatment temperature. The purpose of this study was to compare the properties of CTPs modified by polymer addition with those of a commercial CTP. After the pitch spinning, the obtained green fibers were stabilized and carbonized. The properties of the respective fibers were analyzed to compare their uniformity, diameter change, and mechanical properties. Among three polymer additives, PS220 and PET261 pitches were found to be spinnable, but the carbon fibers from PET261 showed mechanical properties comparable with those of a commercial CTP produced by an air-blowing method (OCI284). The CTPs modified with polymer additive had higher β-resin fractions than the CTP with only thermal treatment indicating a beneficial effect of carbon fiber application.

Preparation of isotropic pitch-based carbon fiber using hyper coal through co-carbonation with ethylene bottom oil

A spinnable pitch was developed from the tetrahydrofuran-soluble fractions (THFS) of hyper coal (HPC) and used to prepare carbon fibers. THFS-derived pitch from bituminous coal-derived HPC showed excellent spinnability and the obtained carbon fibers had a tensile strength of over 800MPa with a diameter of 13μm following heat treatment at 800°C for 5min. Thus, HPC was shown to be a useful alternative precursor for the preparation of low-cost and general-performance carbon fibers.