Polyimide/clay nanocomposites were synthesized via two processes. The one-step process is a polymer-diffusion process, and the two-step process is a monomer-diffusion/in-situ polymerization process. Effect of clay loading, surfactant, solvent-release, and clays on the structural formation and properties of the hybrids were studied. XRD (X-ray-diffractometer), TEM (transmission electron microscopy), FTIR (Fourier-transform infrared spectroscopy), DLS (dynamic light scattering), TGA (thermo-gravimetric analyzer), TMA (thermo-mechanical analyzer), DMA (dynamic mechanical analyzer), and GPA (gas permeability analyzer) were used for the characterization of the clays and composites.
For the effect of clay-loading, it is found that the threshold of clay loading capable of efficiently improving the properties of polyimide (PI) matrix, should be larger than 0.08 ~ 0.31 wt% for the clay with aspect ratio of 200 ~ 50, as judged by the calculation of classical excluded volume argument. For the effect of surfactant, a thermally stable organoclay of 1-methyl-3-octyl-imidazolium chloride modified montmorillonite (8M) displayed the degradation temperature at maximum rate (Td.max) 91 0C higher than that of dodecyl-amine hydrochloride modified montmorillonite (12M). For PI8M hybrid with 5 wt% clay loading, the T10% Loss and Td.max increased 4 0C and 15 0C respectively as compared to that of the neat PI. Besides, two organoclays with improved affinity to solvent NMP (N-methyl-2-pyrrolidone) 18M {octadecylmethyl-bispolyoxylene [15] ammonium chloride modified montmorillonite} and 30B (Methyltallow-bis-2-hydroxyethyl ammonium ion modified montmorillonite) were used to prepare PI/clay nanocomposites. The relative oxygen permeation rate decreased to 0.5 upon the incorporation of these organoclays of 1 wt%, displaying superior improvement on the gas barrier property of polyimide. For the solvent-release effect, the intercalation behavior of the structural formation of PI/clay nanocomposites was studied. The reduction of d-spacing (~1.30 nm) of clay exists in PI/clay nanocomposites even with the case of 1 wt% clay-loading as characterized by XRD and TEM observation. An opposite argument was presented about the explanation to the contraction in galleries of clay with d001~1.30 nm for PI/clay nanocomposites, after the examination of PAA/clay, organoclay/NMP, organoclay, and pristine clay subjected to a specific heating process. We suggest this phenomenon cannot be ascribed to a poly(amic acid) monolayer adopts a flattened conformation is intercalated in the gallery upon thermal elimination of the solvent. And found it is irrelevant to the intercalation of PAA or PI molecules, but is primarily in consequence of the out-flow NMP together with the out-bound surfactants molecules, partial degradation of surfactants, and the re-aggregation of clays induced by the increasing concentration (volume fraction) of clays upon evaporation of NMP. For the effect of different methods of preparation, PI/clay nanocomposites prepared by monomer-diffusion into non-reactive clay (M) process show the higher relative oxygen permeation rate of 0.1, and Td.max of 11 0C as compared to that of hybrids synthesized by polymer-diffusion process. For the effect of different clays, properties of PI/clay nanocomposites prepared by a reactive layered silicic acid of hydrogen-magadiite (H) and nonreactive clay of montmorillonite were studied. The latter displayed a higher Td.max of 7 0C, and the lower relative oxygen permeation rate of 0.07 as compared to the former, demonstrating the better improvement on thermal, and gas barrier properties.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0705105-225951 |
| Date | 05 July 2005 |
| Creators | Hu, Yi-chun |
| Contributors | none, none, none, none, none, none |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0705105-225951 |
| Rights | not_available, Copyright information available at source archive |
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