多壁碳奈米管/高分子奈米複合材料之製備與性質研究

Study on the Preparation and Characterization of Mutilwalled Carbon Nanotube/ Polymer Nanocomposites

阮韶銘(Siu Ming Yuen)

指導教授 ： 馬振基

國立清華大學/工學院/化學工程學系/博士(2008年)

摘要

本論文旨在探討多壁碳奈米管(Multiwalled Carbon Nanotube, MWCNT)之表面改質及不同改質方法對多壁碳奈米管/高分子奈米複合材料性質之影響。針對不同的高分子基材，多壁碳奈米管以不同的方式進行表面改質。將改質之多壁碳奈米管分別加入聚醯亞胺，環氧樹脂及聚甲基丙烯酸甲酯中，製備成不同之多壁碳奈米管/聚醯亞胺，環氧樹脂及聚甲基丙烯酸甲酯等奈米複合材料，並探討其分子運動性，形態學，導電性，機械性質及熱性質。本研究共分為四部份。
本研究第一部份為多壁碳奈米管分別以硫酸/硝酸之混酸，自由基(free radical)，如vinyltriethoxysilane (VTES)改質。而酸改質之多壁碳奈米管分別接枝胺，可溶性聚醯亞胺由(4,4’-(Hexafluoroisopropylidene) diphthalic anhydride(6FDA)與4,4’-Diphenylmethane diisocyanate(MDI)反應而合成) 及矽醇(3-isocyanato-propyltriethoxysilane, IPTES and (3-aminopropyl) triethoxy-silane, APTES)。改質之多壁碳奈米管以FT-IR, Raman spectrum and X-ray photoelectron spectroscopy (XPS)鑑定其結構。未改質及各種已改質之多壁碳奈米管分別與聚醯亞胺混摻，製備成多壁碳奈米管/聚醯亞胺奈米複合材料。
SEM及TEM電子顯微鏡照片顯示未改質多壁碳奈米管在聚醯亞胺基材中呈聚集狀態，而酸改質，胺接枝及可溶性聚醯亞胺接枝多壁碳奈米管在聚醯亞胺基材中分散均勻，矽醇改質多壁碳奈米管在聚醯亞胺基材中互相連接而聚醯亞胺分子則互穿於多壁碳奈米管網狀結構中。聚醯亞胺之表面及體積電阻因為多壁碳奈米管的加入而下降，其機械性質則因為多壁碳奈米管的加入而上升。
酸改質多壁碳奈米管接枝上矽醇(3-isocyanato-propyltriethoxysilane(IPTES)及(3-aminopropyl)triethoxy- silane (APTES)及未改質多壁碳奈米管以自由基反應接枝上vinyltriethoxysilane(VTES)。矽醇改質之多壁碳奈米管加入至聚醯亞胺酸中，在300℃閉環時，聚醯亞胺酸閉環而成聚醯亞胺，同時矽醇改質多壁碳奈米管表面之矽醇則縮合，使多壁碳奈米管互相連接而成為多壁碳奈米管網狀結構，聚醯亞胺分子則互穿於多壁碳奈米管網狀結構中。其體積電阻因矽醇改質多壁碳奈米管的加入而明顯下降，在相同之多壁碳奈米管含量下，其下降幅度比加入酸改質多壁碳奈米管更為明顯。
第二部份為在多壁碳奈米管/環氧樹脂奈米複合材料，未改質多壁碳奈米管及矽醇改質多壁碳奈米管(IPTES)與環氧樹脂摻混，從SEM電子顯微鏡觀察，未改質之多壁碳奈米管在環氧樹脂基材中聚集。環氧樹脂之表面電阻及其體積電阻因多壁碳奈米管的加入而下降。本研究以3-isocyanato-propyltriethoxysilane (IPTES)接枝上DGEBA-type之環氧樹脂及酸改質多壁碳管，將兩者混合，加入交聯劑製備而成矽醇改質多壁碳奈米管(IPTES-MWCNT)/環氧樹脂奈米複合材料。SEM及TEM電子顯微鏡顯示矽醇改質多壁碳奈米管在環氧樹脂中分散均勻，固態13C NMR顯示加入1.0wt%矽醇改質多壁碳奈米管之環氧樹脂之分子運動性下降。以DSC測試之環氧樹脂之玻璃轉移溫度從192.6℃(接枝上IPTES之環氧樹脂)上升至212.5℃ (1.0wt% IPTES-MWCNT)。以DMA測試之環氧樹脂在50℃下之儲存模數(storage modulus)因矽醇改質多壁碳奈米管的加入而上升。環氧樹脂加入1.0wt%矽醇改質多壁碳奈米管，其拉伸及抗折強度分別增加41.65%及145.7%；環氧樹脂加入0.8wt%矽醇改質多壁碳奈米管，其楊氏係數及抗折模數分別增加52.8%及31.1%。
第三部份為多壁碳奈米管以溶膠-凝膠法包覆上一層二氧化鈦，並以矽醇(3-(aminopropyl)triethoxysilane ,APTES)改質二氧化鈦包覆之多壁碳奈米管(AT-MWCNT)並以X-ray photoelectron spectroscopy鑑定，將AT-MWCNT加入DGEBA-type之環氧樹脂中，硬化而成二氧化鈦包覆多壁碳奈米管/環氧樹脂奈米複合材料。其中經過APTES改質之二氧化鈦包覆多壁碳奈米管表面含有胺官能基，能與環氧樹脂反應。二氧化鈦包覆多壁碳奈米管對環氧樹脂之補強效果比未改質多壁碳奈米管優異。在二氧化鈦包覆之多壁碳奈米管系統中，提升二氧化鈦的含量，以X-ray photoelectron spectroscopy (XPS)及X-ray diffraction (XRD) 鑑定二氧化鈦包覆多壁碳奈米管，而環氧樹脂則選用矽醇(APTES)作為交聯劑。TEM電子顯微鏡顯示二氧化鈦已包覆在多壁碳奈米管表面，而加入環氧樹脂後仍未脫落，而且二氧化鈦包覆多壁碳奈米管在環氧樹脂基材中分散均勻。環氧樹脂之機械性質因二氧化鈦包覆多壁碳奈米管的加入而明顯提升。
第四部份為多壁碳奈米管/聚甲基丙烯酸甲酯奈米複合材料，酸改質之多壁碳奈米管接枝上矽醇(3-isocyanato- propyltriethoxysilane, IPTES)。而可交聯之聚甲基丙烯酸甲酯則以甲基丙烯酸甲酯及Vinyltriethoxysilane (VTES)進行共聚合(PMMA-VTES)。矽醇接枝之多壁碳奈米管加入PMMA-VTES基材中而成矽醇接枝多壁碳奈米管/PMMA-VTES奈米複合材料。矽醇之縮合度因矽醇接枝多壁碳奈米管的加入而下降，而矽醇接枝多壁碳奈米管在PMMA-VTES基材中則分散均勻。PMMA-VTES之導電及導熱性都因多壁碳奈米管的加入而上升，而其熱穩定性亦因多壁碳奈米管的加入而明顯增加。

關鍵字

碳奈米管 ； 表面改質 ； 奈米複合材料 ； 聚醯亞胺 ； 環氧樹脂 ； 聚甲基丙烯酸甲脂 ； XPS ； 拉曼光譜, ； SEM ； TEM ； 機械性質 ； 導電性 ； 熱性質

並列摘要

In this research,multi-walled carbon nanotube(MWCNT) was modified with different conditions. The modified MWCNT was analyzed by FT-IR, Raman spectrum and X-ray photoelectron spectroscopy (XPS). The unmodified and modified MWCNT were added to polyimide, epoxy and PMMA to prepare MWCNT/polyimide, MWCNT/epoxy and MWCNT/PMMA nanocomposites. This dissertation contains four parts.
The first part was the preparation and characterization of MWCNT/polyimide composites. Unmodified, acid-modified, amine-modified and soluble polyimide grafted multiwalled carbon nanotube (MWCNT) were added separately to the polyamic acid and heated to 300℃ to form polyimide/carbon nanotube composite. SEM and TEM microphotographs show that acid-modified MWCNT, amine-modified and soluble polyimide grafted MWCNT dispersed uniformly in the polyimide matrix. Silane modified MWCNTs formed interpenetrate network in polyimide network. Effect of the MWCNTs on the surface and volume electrical resistivities of the MWCNT/PI composites has been investigated. Mechanical properties of the nanocomposites were enhanced significantly by modified MWCNTs. Acid modified multiwalled carbon nanotubes (MWCNTs) were grafted with 3-isocyanato-propyltriethoxysilane(IPTES) and (3-aminopropyl) triethoxysilane (APTES); Unmodified multiwalled carbon nanotubes (MWCNTs) were grafted with vinyltriethoxysilane(VTES). Silane grafted MWCNTs were then mixed with the polyamic acid(BDTA/ODA) and heated to 300℃ to form a carbon nanotube/polyimide composite. During the imidization processes, the silanes on the MWCNT surface reacted with each other. TEM microphotographs showed that the silane grafted MWCNTs were connected. The composite material possesses an interpenetrating network in which polyimide molecules were interpenetrated into the MWCNT network. The electrical resistivity of silane grafted MWCNT/polyimide decreased very significantly compared to those only containing acid treated MWCNTs for the same loading with MWCNTs.
The second part was the preparation of MWCNT/epoxy composites, multiwalled Carbon nanotubes (MWCNT)/Epoxy Composites have been prepared. The characteristics and morphological properties were studied. SEM microphotographs showed that MWCNTs were aggregated in the epoxy resin. Epoxy resin and acid modified multiwalled carbon nanotube(MWCNT) were treated with 3-isocyanato- propyltriethoxy-silane (IPTES). SEM and TEM microphotographs of the MWCNT/epoxy composites have been investigated. The molecular motion of silane modified MWCNT/Epoxy composites were studied using high-resolution solid-state 13C NMR. Results show that 1.0wt% silane modified MWCNT/Epoxy exhibits less molecular motion than that of the lower silane modified MWCNT content. Dynamic mechanical analysis (DMA) data of the MWCNT/Epoxy composites showed the storage modulus (at 50℃) and Tgs of the IPTES modified Epoxy increased with IPTES-MWCNT content. Tensile strength and Young’s Modulus of cured silane modified MWCNT(1.0wt%)/Epoxy composites increased significantly comparing to the neat epoxy.
In the third part, a unique titanium oxide (TiO2) coated multiwalled carbon nanotube(MWCNT)/Epoxy has been prepared. Multiwalled carbon nanotubes were coated with a layer of TiO2 and then modified with 3-(aminopropyl)triethoxysilane (APTES). The TiO2 coated MWCNT and APTES modified TiO2 coated MWCNT(AT-MWCNT) were analyzed by X-ray photoelectron spectroscopy(XPS). The AT-MWCNT was added to the Diglycidyl ether of bisphenol A type epoxy to prepare silane grafted TiO2 coated MWCNT/epoxy composites. The amine functional groups on AT-MWCNT surface reacted with epoxy. Consequently, the adhesion between MWCNT and epoxy was improved. Mechanical properties of the AT-MWCNT/epoxy composites increased dramatically. The TiO2 coated MWCNTs/epoxy system was cured with silane. Silane may react with TiO2 surface and improves the adhesion between the MWCNT and epoxy matrix. X-ray photoelectron spectroscopy and X-ray diffraction (XRD) were utilized to analyze the TiO2 coated MWCNTs. TEM microphotographs showed the effect of titanium (IV) n-butoxide on the morphology of the TiO2 coated MWCNT. The dispersion of TiO2 coated MWCNT in the epoxy matrix is better than that of unmodified MWCNT. Mechanical properties of the MWCNT/epoxy composites were improved significantly by the TiO2 coated MWCNTs.
The fourth part was the preparation of MWCNT/PMMA composites. Mutiwalled carbon nanotubes (MWCNT) were modified using 3-isocyanato- propyltriethoxysilane (IPTES). Crosslinkable PMMA was prepared from MMA monomer and Vinyltriethoxysilane (VTES) (PMMA-VTES).The IPTES-modified MWCNT (Si-MWCNT) was mixed with the PMMA-VTES copolymer and crosslinked with catalyst to form Si-MWCNT/PMMA-VTES composites. The degree of condensation of tri-distribution structure of the Si-MWCNT/PMMA-VTES composites decreases as the Si-MWCNT content increases. The morphology of the Si-MWCNT/PMMA-VTES composites was analyzed by SEM and TEM. The MWCNTs were well dispersed in the PMMA-VTES matrix. Surface and volume electrical resistivity decreased as the MWCNT content increased. The thermal conductivity of the PMMA-VTES composites increased by 87.5% when 0.99wt% Si-MWCNT content was added to neat PMMA-VTES. The thermal stability of the PMMA-VTES in nitrogen and air increased significantly even when a small quantity (0.5wt%) of Si-MWCNT was added.

並列關鍵字

Multiwalled carbon nanotube ； surface modification ； nanocomposites ； polyimide ； epoxy ； PMMA ； XPS ； Raman spectroscopy ； SEM ； TEM ； mechanical properties ； electrical resistivity ； thermal conductivity

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