Polyimides are thermally stable at high temperatures. Carbon nano-tubes (CNT) reinforced polymer composites improve multi-functionalities such as structural and thermal properties. We prepared polyimide composites with 0 and 1 wt% CNTs. Three varieties of CNTs: Single Wall � functionalized, Double Wall � functionalized, and Double Wall � non-functionalized CNTs were used. The functionalization is performed by oxidation in acid. Polyimides were prepared using BPADA, BAPP refluxing in anhydrous NMP followed by precipitation, cleaning, dissolving and dispersing CNT. Films of polyimides with and without CNTs were characterized using FT-IR, TGA, DSC, and Positron lifetime spectroscopy (PLS). All samples showed the characteristic peaks of polyimide such as C=O asymmetric/symmetric stretching and bending of imide, C-O-C between two aromatic rings, (CO)2-NC of imide, etc. This confirms the completion of polymerization to form polyimide in all films. TGA curves showed weight loss with temperature in two stages. The first stage 180 - 300 �C showed a weight loss of ~ 15%, that may be associated with the trapped NMP release. The second stage 500 � 750 �C with a drastic weight loss is associated with decomposition. The residual weight is ~ 40% at 750 �C in pure polyimide and functionalized single or double wall. The non-functionalized CNT polyimide showed similar two-step behavior, but the weight loss is remarkably less and about 80% weight remained at 750 �C. DSC curves of all polyimide samples showed two distinguishable endothermic peaks at around 90 �C and 200 �C. The first peak correlated with the onset of NMP release, while 200 �C for structural change. We used PLS to study the micro-porosity of CNT incorporated polyimide composites. The third lifetime component provided the information on pore size (lifetimes) and concentration of pores (intensities) using a simple model, and the values were compared between the films with and without CNT.

CNT-polyimide film synthesis

245th National Meeting (2013)

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