奈米碳管/微膠囊奈米複合材料用於 電致形狀記憶材料之應用

Carbon Nanotube/Microcapsules Nanocomposites for Electro-Active Shape Memory Materials

侯瑋晟(WEI-CHENG HOU)

指導教授 ： 石燕鳳

朝陽科技大學/理工學院/應用化學系/碩士(2020年)

摘要

本研究使用懸浮聚合法製備導熱導電相變微膠囊，使用高分子殼層將相變化材料包覆，以避免相變化材料在相變過程中產生揮發或洩漏等問題，並將導熱導電材料-奈米石墨導入高分子殼層，增加殼層導熱及導電速度；製備的微膠囊具有迅速吸收熱能與降低電阻的特性，並添加於形狀記憶材料中，預期達到提高形狀記憶材料之回復速率，以及輔助複合材料之導電能力，使其可以達到電熱形狀回復功能，以增加形狀記憶材料之應用範圍。首先將甲基丙烯酸甲酯與三乙氧乙烯基矽烷進行預聚合，目的是為了增加殼層與奈米石墨之相容性；再將芯材石蠟與聚乙烯醇懸浮於水溶液中，然後將預聚之殼層加入芯材溶液中，並利用乙二醇二甲基丙烯酸酯做為架橋劑，強化微膠囊殼層強度，最後加入已酸化的奈米石墨，製備成導熱導電相變微膠囊。導熱導電相變微膠囊在粒徑分析與微觀結構分析中，證實所製備的粒徑約為1~2µm，且在微差掃描熱分析中計算包覆率為59.13%。將微膠囊、奈米碳管與聚胺酯混合後，於微觀分析觀察到，微膠囊可以促進奈米碳管分散於複合材料中；微差掃描熱分析也發現隨著導熱相變化微膠囊含量增加，複合材料焓值也呈現上升的趨勢，而熱重分析中複合材料在600℃下，焦炭含量也隨導熱相變微膠囊含量增加而提高；在熱傳導分析中，聚胺酯導熱係數為0.52 W/m×K，添加導熱相變微膠囊及奈米碳管後提升至0.60 W/m×K，聚胺酯電阻率也從2.30×109 Ω/sq下降至0.25×103 Ω/sq，在形狀回復中，可以觀察到在60℃的環境下，聚胺酯回復速率為1.0 degree/min，於加入導熱導電相變微膠囊及奈米碳管後提升至4.2 degree/min。綜合實驗結果得出，所製備之導熱導電相變微膠囊尺寸均一，且具有良好的包覆率及儲熱能力，並在添加於聚胺酯中，擁有提升複合材料儲熱能力、提高導熱係數、降低電阻率以及加速形狀記憶材料回復，以及使形狀記憶材料達到電熱形狀回復等優點。

關鍵字

形狀記憶材料 ； 微膠囊 ； 相變化材料 ； 石蠟 ； 奈米石墨 ； 聚胺酯 ； 懸浮聚合法

並列摘要

In this study, the suspension polymerization method was used to prepare thermally and electrically conductive phase change microcapsules, and the polymer shell can avoid the volatilization or leakage of phase change material (PCM) during the phase change process. Moreover, the incorporation of thermally and electrically conductive material (nano-graphite) into shell can increase the thermal and electrical conductivities of the shell layer. These prepared microcapsules have the characteristics of rapidly absorbing heat energy and reduced electrical resistance, and were subsequently added to the polyurethane (PU) to prepare the shape memory material. It is expected to increase the thermal and electrical conductivities, and recovery rate of the shape memory material, so that it can achieve the electro-thermal shape recovery function and increase the scope of application of shape memory materials. First, the pre-polymer was synthesized by methyl methacrylate (MMA) and triethoxyvinyl silane (TEVS), the incorporation of TEVS is to increase the compatibility of the shell layer and the nano-graphite; second step is to suspend paraffin and polyvinyl alcohol in the aqueous solution as the core material, then the pre-polymer was added to to the core material, and ethylene glycol dimethacrylate (EGDMA) was used as a bridging agent to strengthen the strength of the microcapsule shell layer. Finally, the acidified nano-graphite was added to the solution to prepare a thermally and electrically conductive phase change microcapsule (TECPCM). The prepared microcapsules were composed of a polymer shell layer containing nano-graphite and a paraffin core material, and which have the advantages of high thermal conductivity, high energy storage, low electrical resistance, and the ability to absorb and release thermal energy. In the particle size analysis and microstructure analysis of the microcapsules, it was confirmed that the particle size was about 1~2 µm, and the capsulated ratio of paraffin was 59.13% from the differential scanning thermal analysis. After mixing of TECPCM, carbon nanotubes (CNTs) and PU, it was observed in microscopic analysis that TECPCM can promote the dispersion of CNTs in PU matrix. The results of differential scanning calorimeter (DSC) analysis also reveal that the enthalpy value of the composite material showed an increasing trend as the content of TECPCM increased. The results of thermal gravimetric analyzer (TGA) of the composite material showed that the char yield at 600℃ was also increased with the addition of TECPCM. Moreover, the thermal conductivity of PU was increased from 0.52 W/m‧K to 0.60 W/m‧K, and the electrical resistivity of PU was decreased from 2.30×109Ω/□ to 0.25×103Ω/□ by the addition of TECPCM and CNTs. In the shape recovery test, it can be observed that the recovery rate of PU is 1.0 degree/min at 60℃. While, the recovery rate was increased to 4.2 degree/min by the addition of TECPCM and CNTs. The experimental results show that the size of TECPCM prepared in this study was uniform. Moreover, the capsulated ratio and heat storage capacity of the TECPCM were high, so the composite with this TECPCM can improve its ability of heat storage and thermal conductivity, and reduce its electrical resistivity. Furthermore, the shape memory materials with this TECPCM can achieve the advantages of high recovery rate and both effects of electrical and thermal shape recovery.

並列關鍵字

suspension polymerization ； thermally and electrically conductive phase change microcapsule ； nano-graphite ； polyurethane ； shape memory materials

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