- 學位論文
碳奈米管/聚甲基丙烯酸甲酯複合材料之製備及其性質研究
Preparation and Properties of Carbon Nanotube/Poly(methyl methacrylate) Composites
摘要
本研究藉由Friedel-Crafts Acylation對多壁碳奈米管進行表面改質，接枝馬來酸酐 (Maleic anhydride, Mah)，藉由拉曼光譜 (Raman Spectrum)、高解析電子能譜儀 (XPS)、紅外線光譜儀(FT-IR) 進行定性分析，以TGA作定量分析驗證馬來酸酐在碳奈米管上的含量為5.05 wt%。 本研究將碳奈米管以原位聚合(in-situ)及離位聚合(ex-situ)兩種方式，摻混入PMMA高分子基材中，比較兩種摻混方式下，改質碳奈米管 (Mah-g-MWCNT) 與未改質碳奈米管 (P-MWCNT) 對複合材料之型態學、熱性質、機械性質、及導電性的影響，並製備具有EMI遮蔽效應的碳奈米管/聚甲基丙烯酸甲酯(MWCNT/PMMA)複合材料，以測試該複合材料對EMI遮蔽之效果。 從複合材料橫截面SEM照片可以發現，以原位 (in-situ method)製備出之複合材料的碳奈米管在PMMA高分子基材中較離位 (ex-situ method) 具有較佳的相容性。從複合材料TEM照片可觀察到碳奈米管並未受PMMA高分子影響產生順向排列，而是以隨機方式排列，又in-situ method製備出之複合材料的碳奈米管在PMMA高分子基材中較ex-situ method具有更佳的分散性。 表面電阻及體積電阻測試方面，in-situ method系列較ex-situ method系列具有較低的表面電阻、體積電阻及展透閥值 (percolation threshold)。電磁波遮蔽效應會隨著碳奈米管含量的增加而提升，在相同碳奈米管含量下，則會隨著重疊片數的增加而提升。其中，in-situ method系列所得之電磁波遮蔽數值皆高於ex-situ method系列，而改質碳奈米管之電磁波遮蔽效應之平均值與極值皆低於未改質碳奈米管。此外，磨粉熱壓成型之試片，使複合材料在厚度減少百分之四十之情況下，仍可提升平均電磁波遮蔽效應，且提高適用頻率範圍。 本研究所合成之PMMA高分子基材之玻璃轉移溫度為87.44 oC，而在複合材料方面，其值會隨著改質與未改質碳奈米管之添加量的提升而升高。不同摻混方式比較下， in-situ method 所製備之複合材料具有較高之玻璃轉移溫度。在in-situ method系列中，改質碳奈米管具有較高之玻璃轉移溫度 (4.76 wt% P-MWCNT為101.31 oC；4.76 wt% Mah-g-MWCNT為106.46 oC)。在ex-situ method系列中，改質碳奈米管具有較低之玻璃轉移溫度 (4.76 wt% P-MWCNT為97.40 oC；4.76 wt% Mah-g-MWCNT為96.59 oC)。 本研究製備之複合材料的碳奈米管表面，皆是以in-situ method系列具有較高之高分子接枝量，P-MWCNT/in-situ：8.17 wt%、P-MWCNT/ex-situ：1.12 wt%、Mah-g-MWCNT/in-situ：11.77 wt%、Mah-g-MWCNT/ex-situ：6.69 wt%。並以ATR鑑定MWCNT/PMMA複合材料中之碳奈米管表面接枝官能基。 本研究自行合成之PMMA高分子基材在50oC時之儲存模數為503.3MPa，且四個系列皆會因為碳奈米管的添加造成加強效應(stiffening effect)，使儲存模數隨著碳奈米管添加量的增加而提升。in-situ method製備之複合材料，在儲存模數上之提升較ex-situ method系列來得高。而碳奈米管表面經由化學改質後，表面接枝有馬來酸酐官能基，因此較能有效藉由碳奈米管傳遞荷重，導致該複合材料具有較強之機械強度，因而具有較高之儲存模數 (複合材料在50oC時之儲存模數：4.76 wt% P-MWCNT/in-situ為1047.9 MPa；4.76 wt% P-MWCNT/ex-situ為994.7 MPa；4.76 wt% Mah-g-MWCNT/in-situ為1446.6 MPa；4.76 wt% Mah-g -MWCNT/ex-situ為1214.6 MPa)。 耐磨耗機械性質研究結果顯示，當碳奈米管添加入PMMA高分子基材後，會導致磨耗重量損失增加。然而，當碳奈米管添加量高於展透閥值 (percolation threshold) 時，碳奈米管會在高分子基材中形成網狀結構，因而大幅度提升材料與高分子基材之結合度，進而提升材料之耐磨耗特性，降低磨耗重量損失。此外，in-situ method系列具有較佳的耐磨耗特性，其中，又以in-situ method製備之Mah-g-MWCNT/PMMA複合材料具有最低之磨耗重量損失，具有最佳的耐磨耗特性。
並列摘要
The functionalized multi-walled carbon nanotubes (MWCNT) had been prepared via Friedle-Crafts acylation with maleic anhydride. Raman spectra, X-ray photoelectron spectroscope (XPS), and Fourier transform infrared spectrometer (FT-IR) were utilized to characterize the functionalization of MWCNT. Thermogravimetric analysis (TGA) was used to calculate the organic contents of maleic anhydride modified MWCNT (Mah-g-MWNT), which were 5.05wt%. The composites with MWCNT and poly(methyl methacrylate) (PMMA) were then prepared by the in-situ and ex-situ solution polymerization system. SEM and TEM microphotographs reveal that the MWCNT/PMMA composites process better compatibility and uniform dispersion in the in-situ method system than in the ex-situ method system. MWCNT/PMMA composites prepared by the in-situ method exhibit a lower surface electrical resistivity, a lower volume resistivity, and a lower percolation threshold. The Electromagnetic Interference (EMI) shielding effectiveness (SE) of MWCNT/PMMA composites increased with the increasing of the MWCNT content. Additionally, the in-situ system shows higher EMI SE value, and the Mah-g-MWCNT/PMMA composites exhibit lower EMI SE value than that of the P-MWCNT/PMMA composites. The glass transition temperature (Tg) of PMMA was 87.44oC, and it was increased with the increasing of MWCNT content. Additionally, in the in-situ method system, the Mah-g-MWCNT showed higher Tg (101.31 oC for 4.76wt% P-MWCNT；106.46 oC for 4.76 wt% Mah-g-MWCNT). However, in the ex-situ method system, the Mah-g-MWCNT showed lower Tg (97.40 oC for 4.76 wt% P-MWCNT；96.59 oC for 4.76 wt% Mah-g-MWCNT). The organic contents of PMMA grafted MWCNT in the MWCNT/PMMA composites were calculated by TGA. The in-situ method system processed higher organic contents than in the ex-situ method system. (P-MWCNT/in-situ：8.17 wt%、P-MWCNT/ex-situ：1.12 wt%、Mah-g-MWCNT/in-situ：11.77 wt%、Mah-g-MWCNT/ex-situ：6.69 wt%). Attenuated total reflectance FTIR (ATR-FTIR) was utilized to confirm the quantity of PMMA grafted on the MWCNT. The dynamic mechanical analyser (DMA) showed that the storage modulus of PMMA at 50oC was 503.3 MPa. The storage modulus was increased by the stiffening effect of the MWCNT. The increment of storage modulus in the in-situ method system was higher than that of the ex-situ method system. Additionally, the Maleic anhydride grafted on the surface of MWCNT would improve the load transfer efficiency, which increased the storage modulus. (The storage modulus of 4.76 wt% MWCNT/PMMA composites at 50oC：for P-MWCNT/in-situ is 1047.9 MPa；for P-MWCNT/ex-situ is 994.7 MPa；for Mah-g-MWCNT/in-situ is 1446.6 MPa；and for Mah-g -MWCNT/ex-situ is 1214.6 MPa) The wear resistance decreased at lower MWCNTs loading. However, it was enhanced while the weight fraction of the MWCNT was above the percolation threshold, and the in-situ method system exhibited better wear resistance. Additionally, the Mah-g-MWCNT/PMMA composite in the in-situ method system showed better wear resistance than that of the pristine MWCNT/PMMA composite.
參考文獻
延伸閱讀
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