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Title: Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber

Abstract

Current high-strength carbon fibers (CFs) are mostly derived from PAN polymer precursor, which are very expensive with limited usage in the high-end products. On the other hand, it has also stimulated research interest to develop new low-cost precursors and manufacturing process. Despite numerous studies, researchers have yet to develop a new polymeric precursor that is less expensive, melt-spinnable, and offers a high C-yield. In this three-year R&D project, we proposed three consecutive research phases, including (i) the development of new polyolefin-based precursors that can be thermally transformed to C material in one heating step under inert atmosphere and achieved a C-yield >80%, which is more than 60% higher than that of current PAN precursor, (ii) With the suitable new polyolefin-based precursor, we can focus on CF manufacturing process, including fiber spinning, stabilization, and carbonization, to form high quality carbon fibers with the desirable polymorphous morphology, and (iii) the investigation of thermal conversion process under tension for converting polyolefin-based precursor fibers to high tensile strength carbon fibers with specific graphite crystallite size, orientation of basal line, order-disorder ratio, fiber diameter, and reduced structural defect (voids). The objective is to manufacture low-cost polyolefin-based carbon fibers with high mechanical strength like Toray T700Smore » fiber. Overall, we have successfully completed first two tasks with good experimental results, but the last one requires the close collaboration with ORNL CF team (through the LightMat consortium) in fiber melt-spinning process and carbonization under tension. Due to the Covid-19 pandemic with more than a year ORNL facility unavailable to us, the experimental results in this task are limited. The major R&D activities and findings accomplished during this project are summarized below: In the first R&D phase, we focused on the development of chemical routes to prepare new polymer precursors with the objective to identify the suitable structure that is processible for fiber spinning and can be thermally converted to C with high C yield >80% (more than 60% higher than that of current PAN precursor that exhibits C yield ~50%). All the synthesized polymers were characterized by NMR and GPC to understand their detailed polymer structure and molecular weight, then thermally converting to C structure by one-step heating to high carbonization temperatures under an inert atmosphere. Overall, we have successfully discovered four new C precursors, including P(PA-A), P(PA-PA), PE-g-Pitch, and B-Pitch, they are processible and exhibit very high C yields (higher than Phase I project objective of 80%). The experimental results were also confirmed by the ORNL CF team. In second phase, we focused on the most interesting (low-cost) PE-g-Pitch precursor. The objective was to identify the graft polymer microstructure composition that can simultaneously offer good fiber melt-spinning, high C-yield, and desirable morphology. Two chemical routes were developed, involving PE-DPA and PE-BrSt copolymers, respectively. Both can engage coupling (cycloaddition) reaction with Pitch (PAH) molecules. The PE-g-Pitch precursor derived from PE-BrSt copolymer, exhibiting high molecular weight and narrow composition distribution, shows better fiber-spinning capability and forms carbon fibers with higher C yield and suitable polymorphous morphology. Several key findings are listed below: • The suitable PE-g-Pitch precursor composition, containing PE-g-Pitch graft polymer (20-60 wt.%) and some free Pitch (40-80 wt.%) serving as plasticizer, for melt-spinning to form the corresponding uniform precursor fibers. This operation was carried out at both ORNL and Penn State facilities. • The resulting PE-g-Pitch precursor fibers were carbonized to the corresponding carbon fibers with C content >96% and C-yield >65% in one-step thermal heating at 1500 oC under N2 (without any mechanical tension). On the other hand, the production of current commercial PAN precursor fibers requires an expensive solution-spinning process and two steps thermal transformation reactions (stabilization in air and then carbonization under N2) with long conversion time to obtain only ~50% C-yield. • The resulting PE-g-Pitch based carbon fibers show a nano-polycrystalline morphology by XRD and Raman, like those shown in commercial high tensile strength PAN based carbon fibers. In third phase, our plan was to scale-up PE-g-Pitch precursor and collaborate with ORNL team to conduct fiber melt-spinning and the subsequent carbonization under tension to achieve high strength carbon fibers. However, due to the Covid-19 restrictions, the collaboration activities were seriously interrupted. Thus, I decided to investigate another interesting B-Pitch precursor (developed in Phase I). In our proposal, we also suggested the investigation of B-containing precursor that may enhance carbonization reaction, and the resulting B-doped carbon (BCx) fibers may offer higher tensile strength. Some experimental results support these potential benefits. In addition, this B-Pitch precursor was applied in the manufacture of C/C composite with the collaboration of IACMI Institute. Several new findings are summarized below: • We have identified B-Pitch precursor that exhibits desirable melt viscosity and high C yield (~80%) (confirmed by IACMI during the C/C composite manufacturing). • The resulting boron-doped carbon (BCx) show significantly higher crystallinity (smaller d-spacing and larger crystal thickness Lc), comparing with those shown in the corresponding C material derived from regular Pitch precursor under the same thermal conditions. • Furthermore, the resulting BCx materials show better thermal/oxidative stability, especially at the temperature >500 oC. This observation is very important in many C/C composite applications. • With high C yield (~80%), the IACMI team suggests that this B-Pitch precursor can dramatically reduce the current 6 impregnation/pyrolysis cycles to 1 cycle, which will significantly reduce the cost and time of manufacturing C/C composites.« less

Authors:
ORCiD logo
Publication Date:
Research Org.:
Penn State University
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
OSTI Identifier:
1808293
Report Number(s):
DOE-PSU-8096
DOE Contract Number:  
EE0008096
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 36 MATERIALS SCIENCE; carbon fiber; carbon precursor; PE-g-Pitch polymer

Citation Formats

Chung, T. C. Mike. Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber. United States: N. p., 2021. Web. doi:10.2172/1808293.
Chung, T. C. Mike. Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber. United States. https://doi.org/10.2172/1808293
Chung, T. C. Mike. 2021. "Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber". United States. https://doi.org/10.2172/1808293. https://www.osti.gov/servlets/purl/1808293.
@article{osti_1808293,
title = {Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber},
author = {Chung, T. C. Mike},
abstractNote = {Current high-strength carbon fibers (CFs) are mostly derived from PAN polymer precursor, which are very expensive with limited usage in the high-end products. On the other hand, it has also stimulated research interest to develop new low-cost precursors and manufacturing process. Despite numerous studies, researchers have yet to develop a new polymeric precursor that is less expensive, melt-spinnable, and offers a high C-yield. In this three-year R&D project, we proposed three consecutive research phases, including (i) the development of new polyolefin-based precursors that can be thermally transformed to C material in one heating step under inert atmosphere and achieved a C-yield >80%, which is more than 60% higher than that of current PAN precursor, (ii) With the suitable new polyolefin-based precursor, we can focus on CF manufacturing process, including fiber spinning, stabilization, and carbonization, to form high quality carbon fibers with the desirable polymorphous morphology, and (iii) the investigation of thermal conversion process under tension for converting polyolefin-based precursor fibers to high tensile strength carbon fibers with specific graphite crystallite size, orientation of basal line, order-disorder ratio, fiber diameter, and reduced structural defect (voids). The objective is to manufacture low-cost polyolefin-based carbon fibers with high mechanical strength like Toray T700S fiber. Overall, we have successfully completed first two tasks with good experimental results, but the last one requires the close collaboration with ORNL CF team (through the LightMat consortium) in fiber melt-spinning process and carbonization under tension. Due to the Covid-19 pandemic with more than a year ORNL facility unavailable to us, the experimental results in this task are limited. The major R&D activities and findings accomplished during this project are summarized below: In the first R&D phase, we focused on the development of chemical routes to prepare new polymer precursors with the objective to identify the suitable structure that is processible for fiber spinning and can be thermally converted to C with high C yield >80% (more than 60% higher than that of current PAN precursor that exhibits C yield ~50%). All the synthesized polymers were characterized by NMR and GPC to understand their detailed polymer structure and molecular weight, then thermally converting to C structure by one-step heating to high carbonization temperatures under an inert atmosphere. Overall, we have successfully discovered four new C precursors, including P(PA-A), P(PA-PA), PE-g-Pitch, and B-Pitch, they are processible and exhibit very high C yields (higher than Phase I project objective of 80%). The experimental results were also confirmed by the ORNL CF team. In second phase, we focused on the most interesting (low-cost) PE-g-Pitch precursor. The objective was to identify the graft polymer microstructure composition that can simultaneously offer good fiber melt-spinning, high C-yield, and desirable morphology. Two chemical routes were developed, involving PE-DPA and PE-BrSt copolymers, respectively. Both can engage coupling (cycloaddition) reaction with Pitch (PAH) molecules. The PE-g-Pitch precursor derived from PE-BrSt copolymer, exhibiting high molecular weight and narrow composition distribution, shows better fiber-spinning capability and forms carbon fibers with higher C yield and suitable polymorphous morphology. Several key findings are listed below: • The suitable PE-g-Pitch precursor composition, containing PE-g-Pitch graft polymer (20-60 wt.%) and some free Pitch (40-80 wt.%) serving as plasticizer, for melt-spinning to form the corresponding uniform precursor fibers. This operation was carried out at both ORNL and Penn State facilities. • The resulting PE-g-Pitch precursor fibers were carbonized to the corresponding carbon fibers with C content >96% and C-yield >65% in one-step thermal heating at 1500 oC under N2 (without any mechanical tension). On the other hand, the production of current commercial PAN precursor fibers requires an expensive solution-spinning process and two steps thermal transformation reactions (stabilization in air and then carbonization under N2) with long conversion time to obtain only ~50% C-yield. • The resulting PE-g-Pitch based carbon fibers show a nano-polycrystalline morphology by XRD and Raman, like those shown in commercial high tensile strength PAN based carbon fibers. In third phase, our plan was to scale-up PE-g-Pitch precursor and collaborate with ORNL team to conduct fiber melt-spinning and the subsequent carbonization under tension to achieve high strength carbon fibers. However, due to the Covid-19 restrictions, the collaboration activities were seriously interrupted. Thus, I decided to investigate another interesting B-Pitch precursor (developed in Phase I). In our proposal, we also suggested the investigation of B-containing precursor that may enhance carbonization reaction, and the resulting B-doped carbon (BCx) fibers may offer higher tensile strength. Some experimental results support these potential benefits. In addition, this B-Pitch precursor was applied in the manufacture of C/C composite with the collaboration of IACMI Institute. Several new findings are summarized below: • We have identified B-Pitch precursor that exhibits desirable melt viscosity and high C yield (~80%) (confirmed by IACMI during the C/C composite manufacturing). • The resulting boron-doped carbon (BCx) show significantly higher crystallinity (smaller d-spacing and larger crystal thickness Lc), comparing with those shown in the corresponding C material derived from regular Pitch precursor under the same thermal conditions. • Furthermore, the resulting BCx materials show better thermal/oxidative stability, especially at the temperature >500 oC. This observation is very important in many C/C composite applications. • With high C yield (~80%), the IACMI team suggests that this B-Pitch precursor can dramatically reduce the current 6 impregnation/pyrolysis cycles to 1 cycle, which will significantly reduce the cost and time of manufacturing C/C composites.},
doi = {10.2172/1808293},
url = {https://www.osti.gov/biblio/1808293}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2021},
month = {5}
}