The superior material properties of polymer/clay nanocomposites have attracted much research interests in the past years. The hypothesis of polymer stiffening in the vicinity of the nano-c1ay described using the "core-shell" model has not been fully investigated yet. The investigation of the interfacial region by atomic force microscopy (AFM) has provided us with details of the physical state of this region. It was found that the polymer stiffening region could extend as far as 200nm and 100nm from the face and the edge of a nano-clay respectively. Two different degrees of polymer stiffening have been observed from AFM micrographs with the help of amplitude and phase contrasting techniques. The temperature dependant property of the stiffened polymer has been studied using a heating stage, which showed the stiffened polymer was softened with increasing temperature between the studied range, 60°C and 91°C. The relative polymer crystallinity derived from the X-ray diffraction (XRD) data showed a general trend that increases with the clay content, regardless of the clay modification. However, an exception has been observed with the set of bi-axially drawn specimens, of which the highest polymer crystallinity was found to be the neat polymer when compared with the nanocomposites counterpart. It is believed that the presence of nano-c1ay particles restricted the reorientation of the polymer chains upon stress. From the in situ isothermal investigation of polymer crystal growth, it has been found the crystal grown from a nano-clay particle is larger than that from the bulk. This indicated that the crystallisation began at a lower temperature. The nano-clay and polymer crystal orientations have been further studied with X-ray texture analysis. It was found that the polymer chains were not completely aligned alone the extrusion direction as expected. Also, from the annealed specimens it was found that the orientation of the nano-clay particles had been influenced by the relaxation of the polymer chains.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:561104 |
| Date | January 2011 |
| Creators | Chan, Siu Cheong |
| Contributors | Assender, Hazel |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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