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논문 기본 정보
- 자료유형
- 학위논문
- 저자정보
- 지도교수
- 심상은
- 발행연도
- 2013
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PART 1. Sonochemical Grafting of Poly(vinyl alcohol) on Surface of Multiwalled Carbon Nanotubes
Herein, multiwalled carbon nanotubes (MWCNTs) were modified with water soluble polymer, poly(vinyl alcohol, PVA). Using radical scavenging effect of MWCNT, PVA was grafted onto the outside surface of MWCNTs by simple sonication. To control the grafting PVA onto MWCNTs, the sonication power was changed from 300 to 500 W and the irradiation time from 10 to 50 min. Grafted PVA groups on MWCNTs were confirmed by FTIR, TGA, SEM, and TEM. And then dispersion stability of the modified MWCNTs was monitored by turbiscan. The experimental results show that the amounts of PVA on MWCNTs tend to increase with the increase in the sonication power and irradiation time. The more amounts of grafted PVA on MWCNTs induce the higher dispersion stability of modified MWCNTs in hydrophilic media. These findings exhibit that sonochemical modification of MWCNT is facile and controllable for quantitative modulation of their properties.
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PART 2. The Composite Films of PVA-modified MWCNTs and their Properties
In our previous article, chains of poly(vinyl alcohol) (PVA) were successfully grafted onto outside surface of multiwalled carbon nanotubes (MWCNTs) using ultrasound. And it was possible to modulate dispersion stability of PVA-modified MWCNTs in hydrophilic media with control of amounts of grafted PVA on surface of MWCNTs.
In this study, PVA composite films containing the PVA-modified MWCNTs were prepared by wet-casting. We concentrated on dispersion stability of the PVA-modified MWCNTs in PVA polymer matrix, also paid attention to electrical, thermal, and mechanical properties of their composite films that have different loading levels of the modified MWCNTs and different amounts of attached PVA layer on surface of MWCNTs. As a result, we drew two important conclusions: (1) Because of high dispersion stability of the PVA-modified MWCNTs in the hydrophilic PVA matrix, percolation threshold is showed in the vicinity of 0.1 wt% of the PVA-modified MWCNTs content. (2) The modulation of the amount of grafted PVA on surface of MWCNTs and the loading amounts of modified MWCNTs directly exert influence on electrical and mechanical properties of their composite films in loading levels within about 5 wt%.
Herein, multiwalled carbon nanotubes (MWCNTs) were modified with water soluble polymer, poly(vinyl alcohol, PVA). Using radical scavenging effect of MWCNT, PVA was grafted onto the outside surface of MWCNTs by simple sonication. To control the grafting PVA onto MWCNTs, the sonication power was changed from 300 to 500 W and the irradiation time from 10 to 50 min. Grafted PVA groups on MWCNTs were confirmed by FTIR, TGA, SEM, and TEM. And then dispersion stability of the modified MWCNTs was monitored by turbiscan. The experimental results show that the amounts of PVA on MWCNTs tend to increase with the increase in the sonication power and irradiation time. The more amounts of grafted PVA on MWCNTs induce the higher dispersion stability of modified MWCNTs in hydrophilic media. These findings exhibit that sonochemical modification of MWCNT is facile and controllable for quantitative modulation of their properties.
-------------------------------------------------------------
PART 2. The Composite Films of PVA-modified MWCNTs and their Properties
In our previous article, chains of poly(vinyl alcohol) (PVA) were successfully grafted onto outside surface of multiwalled carbon nanotubes (MWCNTs) using ultrasound. And it was possible to modulate dispersion stability of PVA-modified MWCNTs in hydrophilic media with control of amounts of grafted PVA on surface of MWCNTs.
In this study, PVA composite films containing the PVA-modified MWCNTs were prepared by wet-casting. We concentrated on dispersion stability of the PVA-modified MWCNTs in PVA polymer matrix, also paid attention to electrical, thermal, and mechanical properties of their composite films that have different loading levels of the modified MWCNTs and different amounts of attached PVA layer on surface of MWCNTs. As a result, we drew two important conclusions: (1) Because of high dispersion stability of the PVA-modified MWCNTs in the hydrophilic PVA matrix, percolation threshold is showed in the vicinity of 0.1 wt% of the PVA-modified MWCNTs content. (2) The modulation of the amount of grafted PVA on surface of MWCNTs and the loading amounts of modified MWCNTs directly exert influence on electrical and mechanical properties of their composite films in loading levels within about 5 wt%.
목차
Part 1. Sonochemical Grafting of Poly(vinyl alcohol) on Surface of Multiwalled Carbon Nanotubes 1Chapter 1. INTRODUCTION 2Chapter 2. EXPERIMENTAL 72.1 Materials 72.2 Modification of MWCNTs Using Ultrasonication in PVA Aqueous Solution 92.3 Characterization 10Chapter 3. RESULTS AND DISCUSSION 143.1 Ultrasonic degradation of PVA polymer 143.2 Defects of MWCNTs from ultrasound 183.3 Sonochemical reaction of MWCNTs and PVA 163.4. Dispersion stability of raw and PVA-modified MWCNTs 36Chapter 4. CONCLUSIONS 40Part 2. The Composite Films of PVA-modified MWCNTs and their Properties 42Chapter 1. INTRODUCTION 43Chapter 2. EXPERIMENTAL 482.1 Materials 482.2 Modification of MWCNTs using ultrasonication in PVA aqueous Solution 492.3 Preparation of the MWCNT/PVA composite films 502.4 Characterization of the composite films 53Chapter 3. RESULTS AND DISCUSSION 563.1 Optical properties and Dispersion stability of PVA-modified MWCNTs in PVA matrix 563.2. The electrical properties of MWCNT/PVA composite films 613.3. The mechanical properties of MWCNT/PVA composite films 673.4. The thermal properties of MWCNT/PVA composite films 75Chapter 4. CONCLUSIONS 79References 80Part 1. Scheme 1. Chemical structure of repeating unit Poly(vinyl alcohol) 08Part 1. Scheme 2. Fabrication of the PVA-modified MWCNTs 27Part 2. Scheme 1. Fabrication of the MWCNT/PVA Composite Films 52Part 2. Scheme 2. The dispersion of MWCNTs in PVA matrix and the formation of their network 65Part 1. Figure 1. Ultrasonic degradation of raw PVA 15Part 1. Figure 2. FT-Raman graphs of sonicated raw MWCNTs and their defects 20Part 1. Figure 3. An optical image of suspension of cut pieces in the bottom flasks 22Part 1. Figure 4. Average size of cut pieces from raw MWCNTs (pieces in the bottom flasks) 25Part 1. Figure 5. FT-IR images 28Part 1. Figure 6. TGA graphs 31Part 1. Figure 7. TEM Images of the surface of raw MWCNTs and PVA-modified MWCNTs 34Part 1. Figure 8. SEM Images of the surface raw and PVA-modified MWCNTs 35Part 1. Figure 9. Optical images of dispersion stability of raw and modified MWCNTs in the water 38Part 1. Figure 10. Dispersion stability of raw MWCNTs and PVA-modified MWCNTs 39Part 2. Figure 1. Optical images of MWCNT/PVA composite films with different loading concentrations 59Part 2. Figure 1. Optical images of MWCNT/PVA composite films with different ultrasonic conditions 60Part 2. Figure 2. Optical images of MWCNT/PVA composite films with different ultrasonic conditions 60Part 2. Figure 3. Volume resistivity graphs of MWCNT/PVA composite films with variation in loading concentrations 62Part 2. Figure 4. Volume resistivity graphs of MWCNT/PVA composite films with variation in ultrasonic conditions 66Part 2. Figure 5. Tensile stress-strain curve of PVA/MWCNTs Composite Films with variation in loading concentrations 68Part 2. Figure 6. Variations in tensile properties as a function of loading concentrations 69Part 2. Figure 7. Tensile stress-strain curve of PVA/MWCNTs Composite Films variation in ultrasonic conditions 73Part 2. Figure 8. Variations in tensile properties as a function of ultrasonic conditions 74Part 2. Figure 9. Tc calculated by DSC of MWCNT/PVA composite films with variation in loading concentrations 76Part 2. Figure 10. Tc calculated by DSC of MWCNT/PVA composite films with variation in ultrasonic conditions 77Part 2. Figure S1. Thermal conductivity of MWCNT/PVA composite films with different ultrasonic conditions. 78Part 1. Table 1. Reductions in Mw of PVA polymeric solution by effect of sonication power and irradiation time 17Part 2. Table 1. Transsmision values (%) of PVA-modified MWCNTs in the water by Turbiscan 57
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