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Development of wet-spinning process for manufacturing high-strength PAN fiber with improved spinnability : 방사성이 향상된 고강도 PAN 섬유 제조를 위한 습식방사 공정 개발

DC Field Value Language
dc.contributor.advisor유웅열-
dc.contributor.author김용민-
dc.date.accessioned2023-11-20T04:20:15Z-
dc.date.available2023-11-20T04:20:15Z-
dc.date.issued2023-
dc.identifier.other000000179252-
dc.identifier.urihttps://hdl.handle.net/10371/196389-
dc.identifier.urihttps://dcollection.snu.ac.kr/common/orgView/000000179252ko_KR
dc.description학위논문(박사) -- 서울대학교대학원 : 공과대학 재료공학부(하이브리드 재료), 2023. 8. 유웅열.-
dc.description.abstract최근 폴리아크릴로나이트릴(PAN) 섬유가 탄소섬유의 전구체로 사용되는 것이 알려지면서 많은 관심을 받고 있습니다. 탄소섬유는 다양한 분야에서 높은 강도 대비 경량성을 갖는 물성으로 인해 널리 사용되고 있습니다. 그러나 탄소섬유의 성능 요구가 증가하는 반면, 물성 개선에 한계가 있어 PAN 섬유의 기계적 특성 향상 연구가 필요합니다. 이에 본 연구에서는 전기화학적 습식 방사를 도입하여 PAN 섬유의 기계적 특성을 향상시키는 새로운 방법을 개발하였습니다. 또한, PAN 습식 방사와 전기화학적 습식 방사에서 다양한 변수를 최적화하여 고강도 PAN 섬유를 제조하고자 하였습니다.
우선, 양이온이 체인 끝에 함유된 PAN을 디자인하여 중합하고, 이를 섬유로 제조하였습니다. 제조된 섬유의 미세 구조와 기계적 특성을 평가하여 전기화학적 습식 방사에 적합한 PAN 섬유임을 실험적으로 확인하였습니다. 이온화된 PAN은 응고 과정에서 용매 및 비용매의 확산 속도를 변화시키고, PAN 섬유 내 공극을 최소화하며 기계적 특성을 향상시킵니다. 이후에는 일반적으로 사용되는 이온화되지 않은 PAN으로는 전기화학적 습식 방사가 어려워 리튬 염을 첨가하여 전기 전도도를 갖는 PAN 방사 용액을 제조하였습니다. 리튬 염이 포함된 방사 용액은 전압을 가하면 이온화가 가속화되어 전기화학 반응에 의한 물성 증가 효과를 극대화합니다. 또한, 다양한 리튬 염 농도를 통해 방사 용액 내 최적의 리튬 염 농도를 제시하였습니다.
PAN 섬유가 수분에 미치는 영향을 조사하기 위해 균일하게 수증기를 PAN에 도포하였습니다. 균일하게 수증기로 도포된 PAN을 일반적인 습식 방사와 전기화학적 습식 방사로 섬유를 제조하였습니다. 소량의 수분은 제조된 섬유 내 공극을 최소화하고 기계적 특성을 향상시켰습니다. 전기화학적 습식 방사에서는 더 많은 수분을 통해 기계적 특성이 더욱 향상되었습니다.
또한, PAN 섬유의 기계적 특성과 방사성을 향상시키기 위해 바이모달 분자량 분포를 갖는 PAN을 디자인하였습니다. 바이모달 분자량 PAN은 저분자량 PAN으로 인해 점도가 감소하고 방사성이 증가하였습니다. 또한, 고분자량 PAN과 저분자량 PAN의 응고 과정 차이로 인해 섬유 내 결정 구조를 개선하고 기계적 특성을 향상시켰습니다. 다양한 혼합 비율과 분자량 간 비율의 바이모달 분자량 분포 PAN 섬유를 제조하여 적절한 혼합 비율과 분자량 간 비율을 확인하였습니다. 이를 통해, 방사성과 기계적 특성이 모두 향상된 바이모달 분자량 분포 PAN 섬유를 제조하였습니다.
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dc.description.abstractThe use of polyacrylonitrile (PAN) fibers as precursors to carbon fibers has gained significant attention due to their excellent mechanical properties. Carbon fibers are widely employed in various fields for their high strength-to-weight ratio. However, while the industrial demand for the more advanced performance of the carbon fibers, have been rarely improved. Therefore, there is a need for research focused on enhancing the mechanical characteristics of PAN fibers, which directly affect carbon fiber performance.
In this study, electrochemical wet spinning was introduced to improve the mechanical properties of PAN fibers, and PAN design with enhanced spinnability was developed. Moreover, various variables in PAN wet spinning and electrochemical wet spinning were optimized to produce high-strength PAN fibers. By designing cations within PAN suitable for electrochemical wet spinning, PAN was polymerized and spun into fibers. Experimental evaluation of the resulting fibers' microstructure and mechanical properties confirmed their suitability for electrochemical wet spinning. The ionized PAN led to altered diffusion rates of solvents and non-solvents during the coagulation process, minimizing the formation of voids within the PAN fibers and enhancing their mechanical properties. Furthermore, it was challenging to introduce electrochemical wet spinning using commonly available cations without PAN. Hence, a PAN spinning solution with added lithium salt was prepared to achieve electrical conductivity. The inclusion of lithium salt in the spinning solution accelerated ionization upon the applied electrical potential, maximizing the effect of electrochemical reactions on the enhancement of fiber properties. Additionally, various concentrations of lithium salt were explored to determine the optimum concentration within the spinning solution.
To investigate the influence of moisture on PAN fibers, uniform water vapor was applied to PAN. The PAN fibers with uniformly deposited moisture were then fabricated using conventional wet spinning and electrochemical wet spinning methods. The incorporation of a small amount of moisture minimized the formation of voids within the manufactured fibers and improved their mechanical properties. In the case of electrochemical wet spinning, higher moisture content resulted in further enhancements in mechanical characteristics.
To further enhance the mechanical properties and spinnability of PAN fibers, a bimodal molecular weight distribution of PAN was designed. The presence of low molecular weight PAN reduced the viscosity and increased the spinnability of the fibers. Moreover, the differential solidification process between high molecular weight PAN and low molecular weight PAN improved the crystalline structure within the fibers and enhanced their mechanical properties. Through the fabrication of bimodal molecular weight distribution PAN fibers with various mixing ratios and molecular weight ratios, an optimal combination was identified, resulting in improved spinnability and mechanical properties.
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dc.description.tableofcontentsAbstract i
Contents iii
List of figures vi
List of tables xii
Chapter 1. Introduction 1
1.1. PAN polymerization 1
1.2. Conventional manufacturing of PAN fibers 4
1.3. Electrochemical wet-spinning 8
1.4. Research objectives 13
Chapter 2. Cations in PAN polymer and electrochemical wet-spinning 15
2.1. Preparation of PAN with cations 16
2.1.1. Polymerization of PAN with cations 16
2.1.2. Cations effect in PAN dope solution 19
2.2. Electrochemical wet-spinning of PAN fibers 24
2.2.1. Process condition and characterization method 24
2.2.2. Basic characterization 26
2.2.3. Microstructural characterization 31
2.2.4. Mechanical properties 38
2.3. Summary 40
Chapter 3. External salts in PAN dope and electrochemical wet-spinning 41
3.1. Preparation of PAN dope with external salt 43
3.1.1. Polymerization of PAN without cation 43
3.1.2. PAN dope with external salts 44
3.2. Electrochemical wet-spinning of PAN fibers 45
3.2.1. Process condition and characterization method 45
3.2.2 The effect of salts on electrochemical wet-spinning 47
3.2.3. Microstructural and mechanical characterization 55
3.2.4. Optimization of external salt concentration 62
3.3. A mechanism for electrochemical wet-spinning 65
3.4. Summary 67
Chapter 4. The effect of moisture on wet-spinning behavior 68
4.1. Preparation of dried and moisturized PAN 70
4.1.1. PAN drying 70
4.1.2. PAN moisturization 76
4.2. Fabrication of moisturized PAN fibers 81
4.2.1. Process condition and characterization method 81
4.2.2. Basic characterization 83
4.2.3. Microstructural and mechanical characterization 89
4.2.4. Moisturization effects on PAN fibers 104
4.3. Summary 107
Chapter 5. Molecular weight distribution (MWD) and spinnability 108
5.1. Polymer preparation 111
5.1.1. Polymerization of PAN with various molecular weight 111
5.1.2. Preparation of PAN dope with bimodal MWD 113
5.2. Fabrication of PAN fibers using bimodal MWD 117
5.2.1. Process condition and characterization method 117
5.2.2. The effect of MWD on spinnability 119
5.2.3. The effect of MWD on properties of PAN fiber 126
5.3. Summary 149
Chapter 6. Concluding remarks 150
Reference 152
Korean abstract 166
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dc.format.extentxii, 167-
dc.language.isoeng-
dc.publisher서울대학교 대학원-
dc.subject"PAN fiber"-
dc.subject"Electrochemical wet-spinning"-
dc.subject"Mechanical properties"-
dc.subject"Microstructure"-
dc.subject"Bimodal molecular weight distribution"-
dc.subject"spinnability"-
dc.subject.ddc620.11-
dc.titleDevelopment of wet-spinning process for manufacturing high-strength PAN fiber with improved spinnability-
dc.title.alternative방사성이 향상된 고강도 PAN 섬유 제조를 위한 습식방사 공정 개발-
dc.typeThesis-
dc.typeDissertation-
dc.contributor.AlternativeAuthorYong Min Kim-
dc.contributor.department공과대학 재료공학부(하이브리드 재료)-
dc.description.degree박사-
dc.date.awarded2023-08-
dc.identifier.uciI804:11032-000000179252-
dc.identifier.holdings000000000050▲000000000058▲000000179252▲-
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