液晶型環氧樹脂混掺多壁奈米碳管 複合材料之製備及研究

Abstract

本研究目的在於製備一種具有高強度且質輕的航空材料─液晶型環氧樹脂混摻奈米碳管，並對其性質作一系列的探討。 奈米碳管首先經過酸洗處理後，再藉由環氧樹脂加以表面改質，接著利用傅立葉紅外線光譜儀、拉曼光譜儀與穿透式電子顯微鏡進行分析，發現經過改質後的奈米碳管，可以幫助克服碳管之間的凡德瓦力，避免碳管聚集而達到在高分子中均勻分散的目的。 在本研究中將套用數種動力學模型來模擬奈米複合材料的硬化反應。由動力學的研究中可以發現，隨著奈米碳管濃度增加，其熱傳導性質會跟著提升，同時反應速率會隨之增加，因而使得活化能下降。 硬化後的奈米複合材料分別利用熱差掃描計、熱機械分析儀、熱重分析儀、動態機械分析儀以及微硬度測試來分析其熱性質與機械性質。隨著奈米碳管的加入，此複合材料的性質有顯著提升。添加了最佳量2.00 wt%的奈米碳管後，玻璃轉移溫度提升了33.4°C、熱裂解溫度增加了13.8°C、儲存模數增加了15.27% 、tan δ的溫度峰值增加了64.6°C而微硬度則增加了63.3%。由光學與電子顯微鏡的研究中可發現添加奈米碳管後，無論是在液晶相的形成與分支結構的排列中，皆有相當程度的影響。這個結果可用以解釋奈米碳管和液晶環氧樹脂做成的奈米複合材料具有較佳的熱性質及機械性質。 而再高的奈米碳管添加量並未能更進一步增加此複合材料的性質，因為添加了更多量的奈米碳管將使得玻璃化現象提前，且使分子的運動受到限制而導致反應提早進入熱擴散控制階段。而當分子的運動被侷限住，硬化的程度及性質表現將會較預期的來得低，並且需要較長的反應時間以達到完全硬化。

This research focuses on the fabrication and the characterization of carbon nanotubes-liquid crystalline epoxy resin nanocomposites for strong and lightweight aerospace structural applications. The carbon nanotubes (CNTs) are first acid washed and then functionalized with epoxy resins. Functionalized CNTs are characterized by Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy and Transmission Electron Microscopy (TEM) and are found to help disrupt the strong van der Waals force between the nanotubes and prevents them from bundling together for homogeneous dispersion in the polymer matrix. Several kinetic models are employed to study the curing behaviors of the nanocomposites. From the kinetic study, we find that the reaction rate increases and the activation energy decreases with increasing concentrations of carbon nanotubes and this arises from the high thermal conductivity of the carbon nanotubes. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and microhardness tests are applied to characterize the cured nanocomposite materials. The material properties are enhanced by the carbon nanotubes. 2.00 wt% CNT increases the glass transition temperature by 33.4°C, the decomposition temperature by 13.8°C, storage modulus by 15.27%, peak temperature of the tan δ by 64.6°C and the microhardness by 63.3%. The improvements of thermal and mechanical properties of carbon nanotube reinforced liquid crystalline epoxy resin nanocomposites may be explained by the aligned and branched structures observed in optical and electronic microscopy study. Higher CNT concentrations do not further improve the material’s properties because the accelerating effect of CNTs also antedates the vitrification and turns the reaction to diffusion control driven. As the molecular motions are limited, the degree of cure is lower than expected and the samples would require longer curing time.