Synthesis and Characterization of Polyimide（BPDA-ODA）/ Clay Nanocomposites
|摘要:||本研究乃合成聚亞醯胺（BPDA-ODA）/ 黏土奈米複合材料並分析其性質。使用的黏土為蒙特納石（Na+-Montmorillonite）以p-phenylene diamine（PPD）作為夾入劑來改質黏土，製備得有機黏土（PPD-MONT），再以3,3',4,4',-biphenyl tetracarboxylic dianhydride及4,4'-oxydianiline合成聚醯胺酸（BPDA-ODA），將有機黏土與聚醯胺酸在溶劑DMAc中混合，經加熱脫水閉環反應形成聚亞醯胺/ 黏土複合材料，以X-ray繞射分析其是否為奈米複合材料。
經由in-situ FTIR光譜圖分析聚醯胺酸/黏土奈米複合材料亞醯胺化之動力學，發現有機黏土具有催化作用，能降低亞醯胺化溫度及時間，添加5 phr的有機黏土能使得完全亞醯胺化的溫度由300℃降到250℃，並且使得完全亞醯胺化時間降至10 min，使用一級反應來模擬亞醯胺化反應初期，添加5 phr的有機黏土比純的聚醯胺酸的亞醯胺化活化能降低17％。
添加5 phr的有機黏土所形成的聚亞醯胺/黏土奈米複合材料能使5％熱重損失溫度比純的聚亞醯胺提高23℃。在熱膨脹係數方面，添加5 phr有機黏土的聚亞醯胺/黏土複合材料其在230℃的熱膨脹係數較純聚亞醯胺之熱膨脹係數降低20％。在機械性質方面，添加5phr的有機黏土其楊氏模數比純的聚亞醯胺提高16％，而在結晶性質方面，純的BPDA-ODA聚亞醯胺具有結晶性，添加5phr有機黏土會使得其結晶度降低為原來之38％。|
Polyimide /organoclay nanocomposites have been synthesized, and the properties of these polyimide /organoclay nanocomposites were investigated. First, poly(amic acid) consisted of 3,3',4,4',-biphenyl tetracarboxylic dianhydride (BPDA) and 4,4'-oxydianiline (ODA) was synthesized in dimethylacetamide (DMAc). Then Na+-montmorillonite was intercalated with p-phenylene diamine to form organoclay (PPD-MONT), and different amount of organoclay in DMAc was mixed with poly (amic acid) and was cast into films. These organoclay/ poly (amic acid) films were subsequently subject to thermal treatment for converting to BPDA-ODA/clay nanocomposites. It was found that by dispersing a small amount of organoclay in nanometer scale in the poly(amic acid) both the imidization temperature and the imidization time can be reduced through Fourier Transform Infrared analysis. In specific, the imidization temperature was lowered by 50℃( 250℃ versus 300℃) and the imidization time at 250℃ can be reduced to 10 min for achieving a complete imidization. Using a first-order reaction to model the imidization kinetics of poly(amic acid)/organoclay, a 17% drop in activation energy for imidization of 5 phr BPDA-ODA/clay nanocomposites was obtained as compared to the neat BPDA-ODA. The thermal properties of these BPDA-ODA/clay nanocomposites were promoted by the presence of silicate layers. The thermal degradation temperature ( at 5% weight loss ) of 5 phr BPDA-ODA/clay nanocomposites was 23℃ higher than that of neat BPDA-ODA(628℃versus 651℃). Moreover, the in-plane thermal expansion coefficient of 5 phr BPDA-ODA/ clay nanocomposites was reduced by 20% as compared to that of pure BPDA-ODA at 230℃. The degree of crystallinity of 5 phr BPDA-ODA/clay nanocomposites was also reduced by 38% by the presence of silicate layers, whereas, the Young's modulus of 5 phr BPDA-ODA/clay nanocomposites was 16% higher than that of pure BPDA-ODA.