黏土/聚亞醯胺奈米複合材料之合成與性質

Abstract

本論文乃研究探討利用雙官能基之p-phenylenediamine (PPD)和4,4′-oxydianiline (ODA)當膨潤劑改質親水性之Na+-蒙特納石，使成為疏水性且具有反應性之PPD-Mont和ODA-Mont有機黏土。經由X-光繞射儀及穿透式電子顯微鏡(TEM)分析得知，其分別與pyromellitic dianhydride (PMDA)－4,4′-oxydianiline (ODA)和3,3′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA)－4,4′-oxydianiline (ODA)之聚醯胺酸(poly(amic acid))混成反應後，再經亞醯胺化反應形成黏土/聚亞醯胺奈米複合材料。由傅式紅外線光譜儀(FTIR)分析結果得知，在此類之黏土/聚亞醯胺奈米複合材料中，加入2 ﹪之有機黏土於聚醯胺酸中時，亞醯胺化溫度與時間可由300 ℃，60 min降至250 ℃，50 min即可達到100 ﹪的亞醯胺化；而當加入7 ﹪有機黏土時，在250℃則僅需15 min即可達到100 ﹪的亞醯胺化。由一級反應動力學之研究得知，加入7 ﹪有機黏土於聚醯胺酸中時，亞醯胺化反應之活化能(Ea)可降低約20 ﹪。 對於半結晶性聚亞醯胺(PMDA-ODA)高分子之PPD-Mont/ PMDA-ODA奈米複合材料而言，加入7 ﹪PPD-Mont於PMDA-ODA中時，熱裂解溫度較純的PMDA-ODA提高25 ℃；平行薄膜平面(in-plane)及垂直薄膜平面(out-of-plane)的熱膨脹係數皆分別較純的PMDA-ODA下降33 ﹪及50 ﹪；而由動態機械分析(DMA)結果得知，當加入7 ﹪PPD-Mont於PMDA-ODA中時，在50 ℃之儲存模數(E′)及損失模數(E〞)分別較純的PMDA-ODA增加38 ﹪及30 ﹪；從機械性質分析結果發現，其楊氏模數(Young's modulus)較純的PMDA-ODA提高3.5倍，而最大應力(max. stress)及伸長量亦分別較純的PMDA-ODA增加18 ﹪及30 ﹪；對水氣吸收率(moisture absorption)而言，添加3 ﹪PPD-Mont時，較純的PMDA-ODA降低40 ﹪。 對於完全非結晶之聚亞醯胺(BTDA-ODA)高分子之ODA-Mont/ BTDA-ODA奈米複合材料而言，亦有相同之現象。加入7 ﹪ODA-Mont於BTDA-ODA中時，熱裂解溫度較純的BTDA-ODA提高27 ℃；平行薄膜平面的熱膨脹係數較純的BTDA-ODA下降30 ﹪；而由動態機械分析結果得知，加入7 ﹪ODA-Mont時，BTDA-ODA在20 ℃之儲存模數(E′)及損失模數(E〞)分別增加30 ﹪及22 ﹪；而添加7 ﹪ODA-Mont時，其楊氏模數(Young's modulus)較純的BTDA-ODA提高3倍，而最大應力(max. stress)及伸長量亦分別較純的BTDA-ODA增加50 ﹪及20 ﹪；對水氣吸收率(moisture absorption)而言，添加3 ﹪ODA-Mont時，亦較純的BTDA-ODA降低43 ﹪。

Two kinds of clay/polyimide nanocomposites, pyromellitic dianhydride (PMDA)－4,4′-oxydianiline (ODA) and 3,3′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA)－4,4′-oxydianiline (ODA) have been synthesized, and their thermal and mechanical properties were investigated. Poly(amic acid) consisted of PMDA and ODA or BTDA and ODA were synthesized in N,N-dimethylacetamide (DMAc), and then they were mixed with organoclay formed by Na+-montmorillonite (Mont) intercalated with p-phenylenediamine (PPD) and 4,4′-oxydianiline (ODA) (PPD-Mont and ODA-Mont), respectively. Subsequently, these mixtures were cast into films and were subject to thermal treatment in their converion to PPD-Mont/PMDA-ODA or ODA-Mont/BTDA-ODA nanocomposites. The dispersion of layered silicates in polyimide was analyzed with X-ray diffraction and with transmission electron microscopy (TEM). It was found that by dispersing a small amount of organoclay in nanometer scale in the poly(amic acid), both the temperature and the time in the imidization of organoclay/poly(amic acid) can be reduced dramatically as compared to that of pure poly(amic acid). In specific, when two percent of silicate layers were present, the imidization temperature of 2/98 organoclay/poly(amic acid) was lowered by 50℃ (250℃versus 300℃), and the imidization time of 7/93 organoclay/poly(amic acid) at 250℃can be reduced to 15 minutes. A 20 ﹪drop in the activation energy for the imidization of 7/93 organoclay/PMDA-ODA was determined by using the first-order reaction to model in imidization kinetics of organoclay/poly(amic acid) as compared to that of neat PMDA-ODA. Moreover, a 2.5-fold increase in the modulus of PPD-Mont/PMDA-ODA film was obtained as compared to that of pure PMDA-ODA. Both the maximum stress and elongation-for-break of these PPD-Mont/PMDA-ODA nanocomposites increased slightly with the amount of PPD-Mont (i.e. 18 ﹪and 30 ﹪). The largest reduction in the in-plane and in the out-of-plan coefficient of thermal expansion for 7/93 PPD-Mont/PMDA-ODA nanocomposites were 33 ﹪and 50 ﹪respectively as compared to that of pure PMDA-ODA. When the amount of PPD-Mont in PMDA-ODA reached 3 ﹪, a 40 ﹪decrease in moisture absorption of PPD-Mont/PMDA-ODA nanocomposites was reached as compared to that of pure PMDA-ODA. For BTDA-ODA system, a 2-fold increase in the modulus of ODA-Mont/BTDA-ODA film was found as compared to that of pure amorphous BTDA-ODA. The in-plane coefficient of thermal expansion of these ODA-Mont/BTDA-ODA nanocomposites decreased with the amount of ODA-Mont. The maximum increases in the maximum stress and the elongation-for-break of these types of ODA-Mont/BTDA-ODA nanocomposites were 50 ﹪and 20 ﹪respectively as compared to that of pure BTDA-ODA. A 43 ﹪decrease in moisture absorption of 3/97 ODA-Mont/BTDA-ODA nanocomposites was resulted in as compared to that of pure BTDA-ODA.