Title Page
Abstract
Contents
Chapter 1. Introduction 17
1.1. PAN polymerization 17
1.2. Conventional manufacturing of PAN fibers 20
1.3. Electrochemical wet-spinning 24
1.4. Research objectives 29
Chapter 2. Cations in PAN polymer and electrochemical wet-spinning 31
2.1. Preparation of PAN with cations 32
2.1.1. Polymerization of PAN with cations 32
2.1.2. Cations effect in PAN dope solution 35
2.2. Electrochemical wet-spinning of PAN fibers 40
2.2.1. Process condition and characterization method 40
2.2.2. Basic characterization 42
2.2.3. Microstructural characterization 47
2.2.4. Mechanical properties 54
2.3. Summary 56
Chapter 3. External salts in PAN dope and electrochemical wet-spinning 57
3.1. Preparation of PAN dope with external salt 59
3.1.1. Polymerization of PAN without cation 59
3.1.2. PAN dope with external salts 60
3.2. Electrochemical wet-spinning of PAN fibers 61
3.2.1. Process condition and characterization method 61
3.2.2. The effect of salts on electrochemical wet-spinning 63
3.2.3. Microstructural and mechanical characterization 71
3.2.4. Optimization of external salt concentration 78
3.3. A mechanism for electrochemical wet-spinning 81
3.4. Summary 83
Chapter 4. The effect of moisture on wet-spinning behavior 84
4.1. Preparation of dried and moisturized PAN 86
4.1.1. PAN drying 86
4.1.2. PAN moisturization 92
4.2. Fabrication of moisturized PAN fibers 97
4.2.1. Process condition and characterization method 97
4.2.2. Basic characterization 99
4.2.3. Microstructural and mechanical characterization 105
4.2.4. Moisturization effects on PAN fibers 120
4.3. Summary 123
Chapter 5. Molecular weight distribution (MWD) and spinnability 124
5.1. Polymer preparation 127
5.1.1. Polymerization of PAN with various molecular weight 127
5.1.2. Preparation of PAN dope with bimodal MWD 129
5.2. Fabrication of PAN fibers using bimodal MWD 133
5.2.1. Process condition and characterization method 133
5.2.2. The effect of MWD on spinnability 135
5.2.3. The effect of MWD on properties of PAN fiber 142
5.3. Summary 165
Chapter 6. Concluding remarks 166
Reference 168
Korean abstract 182
Table 2-1. Molecular weight and polydispersity index(PDI) of nonPAN and NaPAN. 34
Table 2-2. ¹H NMR analysis of nonPAN and NaPAN. 34
Table 2-3. ICP-AES analysis of nonPAN and NaPAN. 34
Table 2-4. Crystallinity and crystal size of nonPAN and NaPAN fibers. 50
Table 2-5. Void length and angle of nonPAN and NaPAN fibers. 53
Table 3-1. Crystallinity and crystal size of nonPAN and LiPAN fibers. 73
Table 3-2. Void length and angle of nonPAN and LiPAN fibers. 76
Table 4-1. Crystallinity, crystal size and preferred orientation of GPAN fibers. 110
Table 4-2. Crystallinity, crystal size and preferred orientation of EPAN fibers. 115
Table 5-1. Molecular weight and polydispersity index(PDI) of LMW and HMW. 130
Table 5-2. ¹H NMR analysis of LMW and HMW. 130
Table 5-3. Molecular weight and polydispersity index(PDI) of A-LMW, A-HMW, B-LMW and B-HMW. 132
Figure 1-1. Two step processing of PAN into carbon fiber; oxidative stabilization process (left); carbonization (right). Gained from reference [45]. 21
Figure 1-2. A schematic diagram of the wet spinning process. Gained from reference [55]. 22
Figure 1-3. Schematic diagrams of (a) the electrochemical wet-spinning process and (b) the molecular changes occurring during the wet-spinning processes [73]. 28
Figure 2-1. Photograph of nonPAN and NaPAN dope solution. 36
Figure 2-2. (a) Schematic illustrated reactor for applied electric potential at dope solution. (b) Photograph of reactor for applied electric potential at dope solution.... 38
Figure 2-3. Fourier transform infrared (FT-IR) spectra of NaPAN film with both electrodes. 39
Figure 2-4. Scanning electron microscopy (SEM) images of the cross section and surface morphology (a,b) nonPAN_C, (c,d) nonPAN_E, (e,f) NaPAN_C and (g,h) NaPAN_E. 43
Figure 2-5. Fourier transform infrared spectra (FT-IR) of (a) nonPAN fibers, (b) NaPAN fibers. 45
Figure 2-6. Differential scanning calorimetry (DSC) analysis of nonPAN and NaPAN fibers. 46
Figure 2-7. Microstructural characterization of the PAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of (a) nonPAN_C fiber, (b)... 48
Figure 2-8. Two-dimensional small-angle X-ray scattering (2D-SAXS) images of (a) nonPAN_C, (b) nonPAN_E, (c) NaPAN_C and (d) NaPAN_E fibers. 52
Figure 2-9. Void structure characterizations of the fibers. (a) Ruland's linear fittings and (b) void length and orientation of nonPAN_C and nonPAN_E fibers. (c)... 53
Figure 2-10. Mechanical properties of the (a) stress-strain curves of fittings and (b) strength comparison of nonPAN_C and nonPAN_E fibers. (c) Stress-strain curves of... 55
Figure 3-1. Scanning electron microscopy (SEM) images of the cross section and surface morphology (a,b) LiPAN_C and (c,d) LiPAN_E fibers. 64
Figure 3-2. Fourier transform infrared (FT-IR) spectra of LiPAN fibers. 64
Figure 3-3. Fourier transform infrared (FT-IR) spectra of (a) LiPAN_C and (b) LiPAN_E nascent fibers with different coagulation bath lengths. (c) The... 67
Figure 3-4. Thermogravimetric analyzers (TGA) of LiPAN nascent fibers. 68
Figure 3-5. Thermal properties of nonPAN and LiPAN fibers. (a) Differential scanning calorimetry (DSC) analysis and (b) differential thermal analysis(DTA) curves. 70
Figure 3-6. Microstructural characterization of the PAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of (a) LiPAN_C and (b)... 72
Figure 3-7. Two-dimensional small-angle X-ray scattering (2D-SAXS) images of (a) LiPAN_C and (b) LiPAN_E fibers. 74
Figure 3-8. Void structure characterizations of the fibers. (a) Ruland's linear fittings of LiPAN_C and LiPAN_E fibers. Void length and orientation of (b) nonPAN_C and... 75
Figure 3-9. Mechanical properties of the nonPAN_C, LiPAN_C and LiPAN_E fibers. (a) Stress-strain curves and (b) strength comparison of nonPAN_C and... 77
Figure 3-10. Scanning electron microscopy (SEM) images of the surface morphology (a) LiPAN0.5_C, (b) LiPAN0.5, (c) LiPAN3.0_C, (b) LiPAN3.0_E, (c)... 79
Figure 3-11. Mechanical properties of LiPAN_C and LiPAN_E fibers as a function of Li acetate concentration. 80
Figure 3-12. Schematic illustration of cation-enhanced wet spinning (electrochemical wet-spinning with cation) in (a) conductive nozzle (b)... 82
Figure 4-1. Photographs illustrating the drying process of PAN powder. 87
Figure 4-2. Investigations of structural and morphological changes in commercial PAN (CPAN) and dried PAN (DPAN) powders. (a) Fourier transform-in... 90
Figure 4-3. Thermogravimetric analyses (TGA) of commercial and dried PAN (CPAN and DPAN). 91
Figure 4-4. Photograph of lab-made humidifying chamber. 92
Figure 4-5. Change in the water content of DPAN as a function of time. 93
Figure 4-6. Rheological behavior in dope solution. (a) dynamic viscosity curves, (b)Han plots, and (c) Casson plots of dried and moisturized PAN (PAN0, PAN0.5,... 96
Figure 4-7. Scanning electron microscopy (SEM) images of cross-sections and surface structures of GPAN fibers. (a, b) GPAN0, (c, d) GPAN0.5, (e, f)... 100
Figure 4-8. Fourier transform-infrared (FT-IR) spectra of GPAN fibers. 101
Figure 4-9. Scanning electron microscopy images of the cross-sections and surface structures of EPAN fibers: (a, b) EPAN0, (c, d) EPAN0.5, (e, f) EP... 103
Figure 4-10. Fourier transform-infrared (FT-IR) spectra of EPAN fibers. 104
Figure 4-11. Void structure characterization of GPAN fibers. Two-dimensional small-angle X-ray scattering (2D-SAXS) images. 106
Figure 4-12. Void structure characterizations of the GPAN fibers. (a) Ruland linear fittings, and (b) void angle and void length. 107
Figure 4-13. Microstructural characterizations of the GPAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of (a) GPAN0, (b)... 111
Figure 4-14. Void structure characterization of GPAN fibers. Two-dimensional small-angle X-ray scattering (2D-SAXS) images. 113
Figure 4-15. Void structure characterization of the EPAN fibers. (a) Ruland linear fittings, and (b) void orientation and void length. 114
Figure 4-16. Microstructural characterization of the EPAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of (a) EPAN0, (b) EPAN0.5, (c)... 116
Figure 4-17. Mechanical properties of the GPAN and EPAN fibers. (a, b) Stress- strain curves of (a) GPAN and (b) EPAN fibers. (c) Strength comparison of GPAN... 119
Figure 4-18. Schematic illustration of PAN-MA molecules with adsorbed water. Electrostatic potential maps of (a) raw, (b) hydrated, and (c) demethylate... 122
Figure 5-1. Viscosity of bimodal MWD PAN (HMW0, HMW25, HMW50, HMW75 and HMW100) in dope solution. (a) dynamic viscosity curves and (b)... 136
Figure 5-2. Rheological behavior in dope solutions. (a) Han plots, and (b) Casson plots of bimodal MWD PAN dope solutions (HMW0, HMW25, HMW50, HMW75... 138
Figure 5-3. Rheological behavior of A-bimodal MWD PAN (A-HMW0, A-HMW25, A-HMW50, A-HMW75 and A-HMW100) in dope solution. (a) dynamic... 140
Figure 5-4. Rheological behavior of B-bimodal MWD PAN (B-HMW0, B-HMW25, B-HMW50, B-HMW75 and B-HMW100) in dope solution. (a) dynamic... 141
Figure 5-5. Scanning electron microscopy(SEM) images of surface structures of bimodal MWD PAN fibers. (a) HMW0, (b) HMW25 (c) HMW50, (d) H... 143
Figure 5-6. Fourier transform infrared spectra(FT-IR) of bimodal MWD PAN fibers (HMW0, HMW25, HMW50, HMW75 and HMW100). 144
Figure 5-7. Microstructural characterizations of the bimodal molecular weight PAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) ima... 146
Figure 5-8. (a) Crystallinity, (b) crystal size and (c) preferred orientation of bimodal MWD PAN fibers (HMW0, HMW25, HMW50, HMW75 and HMW100). 149
Figure 5-9. Two-dimensional small-angle X-ray scattering (2D-SAXS) images of (a) HMW0, (b) HMW25, (c) HMW50, (d) HMW75 and (e) HMW100 fibers 151
Figure 5-10. Void structure characterizations of the fibers. (a) Ruland's linear fittings and (b) void length and (c) angle of bimodal MWD PAN fibers... 152
Figure 5-11. Mechanical properties of the (a) specific stress-strain curves (b) specific strength comparison of bimodal MWD PAN fibers (HMW0, HMW... 154
Figure 5-12. Microstructural characterizations of the A-bimodal MWD PAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of... 157
Figure 5-13. (a) Crystallinity and (b) crystal size of A-bimodal MWDPAN fibers (A-HMW0, A-HMW25, A-HMW50, A-HMW75 and A-HMW100). 158
Figure 5-14. Microstructural characterizations of the B-bimodal MWD PAN fibers. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) images of... 161
Figure 5-15. (a) Crystallinity and (b) crystal size of B-bimodal MWD PAN fibers (B-HMW67, B-HMW80, B-HMW90, B-HMW95 and B-HMW100). 162
Figure 5-16. Specific strength of the (a) A-bimodal MWD PAN fibers (A-HMW0, A-HMW25, A-HMW50, A-HMW75 and A-HMW100) and (b) B-bimodal... 164