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  • 學位論文

利用化學誘發相分離法製備多孔性熱固型環氧樹脂材料及其特性分析

Preparation and Characterization of Porous Epoxy Thermosets via Chemically Induced Phase Separation

指導教授 : 鄭國忠
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摘要


本研究利用環氧樹脂和不同胺類硬化劑反應系統,以化學誘發相分離法製備多孔性熱固型環氧樹脂材料。實驗中以二異丁酮(diisobutyl ketone, DIBK)為溶劑,雙酚A型的環氧樹脂(D.E.R.331)分別與三級胺2,4,6-三(二甲胺基甲基)苯酚(2,4,6-tris(dimethylaminomethyl)phenol, DMP-30)為硬化劑系統與二乙烯三胺(diethylenetriamine, DETA)一級胺為硬化劑系統,於硬化反應的過程中,由於高分子的分子量上升使得混合熵( )降低誘發高分子與溶劑溶解度下降而相分離,製備出多孔性環氧樹脂材料。研究結果發現,D.E.R. 331/ DMP-30系統硬化後的環氧樹脂材料呈現多孔及孔洞互相連接(interconnected pore)的開放式形態,而多孔性環氧樹脂材料的孔徑尺寸會隨著溶劑含量增加從0.18 μm增大至2.33 μm;整體孔隙度則也從0.33增加至0.60,隨著反應溫度的上升和硬化劑含量的增加,製備出的多孔性環氧樹脂材料之孔徑尺寸則會愈小。藉由乙醇滲透率的測試中證實,硬化後的環氧樹脂材料呈現開放式孔洞形態,根據不同的孔隙度大小其乙醇滲透率約在2至4700 L / (m2.h.bar)之間。此外利用滲透阻力模式建立探討材料阻力對乙醇滲透率之影響,結果發現乙醇滲透率較低時,多孔性環氧樹脂材料表面層阻力會較內部阻力的影響要大。由熱性質分析得知,多孔性環氧樹脂材料最大裂解溫度均高於440 ℃,Tg溫度約115 ℃以上,表示製備後的多孔性環氧樹脂材料具有高熱穩定性的優點。由機械性質分析中得知,多孔性環氧樹脂材料之楊氏模數約在0.7至2.0 GPa,抗張強度則在6.3至31.1 MPa之間。 在D.E.R. 331/ DETA系統中發現,硬化後的熱固型環氧樹脂材料呈現多孔及蜂窩狀封閉式形態,環氧樹脂材料內部的孔洞形態可藉由不同的溶劑含量來調控,當溶劑DIBK含量超過30 vol.%以上時化學誘發相分離開始產生,材料內部的孔徑尺寸大約在4 μm左右,當溶劑DIBK含量超過40和50 vol.%時,材料內部的孔徑尺寸分別增加至約4.5 μm和9 μm。而環氧樹脂材表面的孔洞形態除了可藉由不同的溶劑含量,也可利用不同的接觸界面,於硬化反應期間,由於高分子溶液和固體界面彼此潤濕程度的不同而控制。高分子富相/固體界面間的表面張力與溶劑富相/固體界面間的表面張力值的不同,會直接影響到高分子溶液和固體界面相分離時的程序,而造成硬化後多孔性環氧樹脂材料擁有不同的表面形態,因此可藉由不同的接觸界面製備出相同的內部孔洞結構而不同的表面孔洞形態。 為了進一步了解環氧樹脂與不同胺類硬化劑系統於化學誘發相分離過程及其反應機制。本研究利用相位差顯微鏡、DSC和流變儀,觀察並記錄不同胺類硬化劑系統於反應過程中之變化。由DSC實驗結果中發現,D.E.R. 331/DMP-30系統於DSC圖譜上有兩個明顯的放熱峰存在,而D.E.R. 331/DETA系統則僅有一個放熱峰,可表示兩系統的反應機制是不相同的,推論會造成兩系統於硬化後環氧樹脂材料在孔洞結構上的差異。而由相位差顯微鏡觀察相分離過程中發現,D.E.R. 331/DMP-30系統於反應初期時有部分粒狀顆粒析出,因此系統有可能是經由高分子富相的成核(initial nucleation)而形成顆粒彼此連接在一起並分散於溶劑富相中形成雙連續結構,或者是系統初期為旋節分裂(spinodal decomposition)相分離機制之後系統達到凝膠化(gelation)結構固定,因此硬化後環氧樹脂薄膜為開放式的孔洞結構。而在D.E.R. 331/DETA系統可能是經由成核成長(nucleation and growth)相分離機制進入到介穩態區,相分離後溶劑富相形成之核胞隨著反應進行會不斷的成長與合併直到系統達到凝膠化結構固定,因此硬化後環氧樹脂薄膜為蜂窩狀的封閉式孔洞結構。由黏彈性質分析中發現,由於兩種硬化反應系統之反應機制的不同,在D.E.R. 331/DMP-30系統隨著硬化反應進行其儲存模數G'、損失模數G'和複合黏度會有兩段的上升曲線,而D.E.R. 331/DETA系統則只有一段的上升曲線,此外也發現D.E.R. 331/DMP-30系統於相分離後其儲存模數G'、損失模數G'曲線接近,而影響高分子富相或溶劑富相於相分離後其尺度上成長受到限制,因此硬化後環氧樹脂薄膜孔洞結構會較小。 環氧樹脂和二種不同硬化劑系統依不同比例混合,於相同的溶劑含量下,利用化學誘發相分離法可製備出不同孔洞結構之多孔性環氧樹脂材料。環氧樹脂D.E.R. 331和硬化劑DMP-30/DETA 混合,隨著硬化劑DETA的比例增加,環氧樹脂材料截面孔徑尺寸會愈大,當DMP-30/DETA為1/1和0/1時,材料截面孔洞形態會由原本的內部通孔形態轉變為封閉式的孔洞形態。而環氧樹脂和DMP-30/DETA混合,隨者DETA的比例增加材料表面孔徑尺寸會逐漸縮小,當DMP-30/DETA超過1/0.4時材料表面開始呈現緻密形態。 因此可藉由反應組成、反應溫度、硬化劑種類、硬化劑含量和接觸界面等條件控制薄膜孔洞形態之外,也可根據環氧樹脂和不同比例硬化劑混合,製備出不同的孔洞結構和不同孔隙度範圍之多孔性環氧樹脂材料。期望能應用於例如:低介電材料、多孔性的隔熱材、層析儀用管柱、膜過濾及分離應用、經由纖維強化的人工關節減輕其重量和增加透氣性,和鋰電池中作為耐熱絕緣多孔性黏著劑,使隔離膜有好的熱阻斷效果及穿透力並在安全上多了一個設計。

並列摘要


Epoxy thermosets were prepared from a commercial epoxy resin, D.E.R. 331 cured with a tertiary amine, 2,4,6-tris-(dimethylaminomethyl) phenol (DMP-30) in the presence of a solvent, diisobutyl ketone (DIBK). During the curing process, the polymerization resulted in an increase in the molecular weight of polymer and a decrease in its solubility in DIBK; the solution thus phase-separated, usually referred to as chemically induced phase separation (CIPS). The phase separation formed solvent rich phase that then became interconnected pores after the removal of DIBK. By varying the content of DIBK from 32 to 40 vol.% , the epoxy thermosets with interconnected pores were prepared, of which surface pore size ranging from 0.20 to 2.33 μm, overall porosity from 0.41 to 0.60, and ethanol permeability from 10 to 4717 L/(m2.h.bar). The glass transition temperatures of the epoxy thermosets, determined by differential scanning calorimetry, were all higher than 100oC. The thermal stability of the porous epoxy thermosets were further investigated by thermal gravimetry analysis. It was found that temperatures of 5% weight loss, were higher than 350oC. A novel and simple method for producing epoxy thermoset with controlled surface morphology is demonstrated in this study. The epoxy thermosets were made via stepwise polymerization of a mixture of epoxy resin, D.E.R. 331, and diethylene triamine in diisobutyl ketone (DIBK). Both the surface and bulk morphology of the cured polymers are dependent on the solvent fraction of the reactive solution. With higher than about 30 vol.% of DIBK, the chemically induced phase separation, CIPS, occurred during polymerization, and closed spherical pores, about 4 μm in diameter, appeared in the bulk of the cross-linked polymers, which increased to about 4.5, and 9 μm when the solvent was increased to 40, and 50vol.%, respectively. The surface morphology of the epoxy thermosets might be different from that in the bulk. Smaller pore size or dense skin was formed via the CIPS process, which can be tailored by covering the reactive solution with different contacting films during cure. The competition between the solvent-rich and polymer-rich phase absorbed onto the surface of contacting film could change the surface morphology. Therefore, the porous epoxy thermosets having similar bulk morphology could be prepared with a variety of surface structures. In order to understand the different mechanism of phase separation between the porous epoxy thermosets cured by DMP-30 and DETA. A DSC and rheometer were further used to monitor the phase separation process. The DSC curve for the solution cured with DMP-30 shows a phase separation behavior much different from that cured with DETA. For the system with DMP-30, there are two main exothermic peaks on the DSC curve, the first peak is considered to be contributed a quaternary ammonium alcoholate formed via the initiation reaction of the epoxy and tertiary amine groups, and the second one from the chain propagation proceeds by the active site via the anionic polymerization. While, for the system with DETA, via a step-wise polymerization only one exothermic peak was found during the curing process. The rheological results as indicated, the D.E.R. 331/DMP-30 system after phase separation, its storage modulus and loss modulud curves was closing mean that the polymer-rich domain was easier to gel and the domain size of polymer rich or solvent rich was small. Different structures of the cured epoxy thermosets have been observed in the epoxy resin, D.E.R. 331 cured with DMP-30/DETA curing agents mixture, in the presence of a solvent, diisobutyl ketone (DIBK) via chemically induced phase separation. The epoxy thermosets increase in pore size of cross-section and decrease in pore size of surface with increasing amount of DETA. Moreover, have the dense structure of the surface epoxy thermoset, while the content of DMP-30/DETA was increased to 1/0.4. When mixture of curing agent DMP-30/DETA was 1/1 and 0/1, the pore structure of epoxy thermoset transform from interconnected pore into close pore mophology.

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