الفهرس 
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Abstract
This thesis is divided into three main chapters; introduction, experimental, and results and discussion:
INTRODUCTION: Include the definition of nanotechnology, and materials in the nanoscale, and reviewed the composition and properties of the clay (bentonite), and operations of modification (which is the nano-fillers used in this study). As well as the definition of polymer nanocomposites especially polymer/ clay nanocomposites , and its types. Polyurethane (as a matrix for such material polymer/ clay nanocomposites used in this study), was defined and its component of the polyol and diisocynate materials. Also the application of these polyurethane/clay nanocomposites was reviewed, been back to many of the research published worldwide in this field. The introduction also includes the electrical properties of polymeric materials, in general, and polymer/ clay nanocomposites in particular, such as electrical conductivity in different forms, dielectric properties, thermal properties. |The mechanical properties of polymeric composites materials, such as stress and strain, and tensile strength, also included those provided to many research published in scientific journals and the test methods and scientific references.
EXPERIMENTALS: This part includes two main parts:
Fist part: The listing of all chemicals used in this study and their properties and sources.
Second part: : Includes methods of preparation and in vivo experiments to achieve the goal of the study.
Which included the modification methods of Egyptian bentonite represented in the its purification, converting it to Na-Bentonite and its analysis. The determination method and calculation of cationic capacity exchange, and then how to prepare nanoscale organic bentonite using four different surfactants with different lengths of the main alkyl chain and different branching) which are; octadecylamine (ODA), dedocylamine (DDA), cetyltrimethylamonium bromide (CTAB), and 3-aminopropyltri-ethoxysilane (APTES). The preparation method of polyurethane /Organo-Bentonite nanocomposites were reported.
This part also includes the different techniques used for studying the properties of the prepared nanocomposites using, FTIR, X-ray diffraction, Transition Electron microscope, thermal analysis and thermo-gravimetric analysis. Also swelling, mechanical, electrical conductivity and dielectric measurements were reported.
RESULTS and DISSCUSIONS:
This part is concerning with studying the effect of the modification of the Egyptian Bentonite (EB) using four different modifiers on the physical properties of polymer nanocomposites with this modified Bentonite (Organo-Bentonite or Nano-Bentonite) as a filler. Polyurethane was selected as a matrix for these prepared nanocomposites. These Polyurethane/Organo-Bentonite were evaluated from studying their morphology and their mechanical, swelling characteristics.
This study is divided into main three parts:
The First Part: (Modification of Bentonite to nano-Bentonite (Organo-Bentonite)).
Includes study and preparation of the organo-Bentonite from Egyptian Bentonite using four different surfactant materials, and its evaluation as inorganic reinforcement filler in nano scale in polyurethane nanocomposites .
The Egyptian Bentonite was firstly purified to remove impurities then activated using Na-Cl. The activation was evaluated by EDX (energy dispersive X- ray). Then the EB was modified to be Organo-Bentonite using octadecylamine (ODA), dedocylamine (DDA), cetyltrimethylamonium bromide (CTAB), and 3-aminopropyltri-ethoxysilane (APTES) salts. The morphology of the unmodified (Na-B) and the four Organo-Bentonites were studied using FTIR, TGA, WAXD and TEM. The results reveal that the layer galleries of Bentonite were expanded due to the modification of the different surfactants, which contained a long-chain alkyl group. The d-spacing of the O-B increase in the following order:
ODA-B > DDA-B > Silane-B ~ CTAB-B.
The Second Part:(Study of Polyurethane/ Different Type of Organo-Bentonite Nanocomposites)
Includes study of Polyurethane nanocomposites with different content of the O-B (0.25, 0.50, 0.75, 1, 3 and 5 wt.%) using the four different types of the modified Organo-Bentonite. Also the Polyurethane composites filled with unmodified Na-B was used for comparison. The morphology of all the samples were studied using XRD and TEM. As well as the mechanical properties, including tensile strength, elongation at break and Young’s modulus, were studied and also elucidated by using phenomological theory of rubber elastisty
Using the swelling data of the specimen in solvents, the molecular weight and the crosslink density of the nanocomposites with different concentrations were determined.
The obtained data refer to:
• The morphology of PU/O-Bs elucidate that PU chains can only be intercalated to the Bentonite layers, without the formation of exfoliated structure.
• The maximum values in the tensile properties of nanocomposites was obtained with for all the nanocomposites at 0.25 wt % O-B content.
The tensile strength of the nanocomposites increase in the following order:
ODA-B ˃ DDA-B ˃ Silane ˃ CTAB.
• The maximum degree of swelling was affected by the weight content of the organobentonite. Also there was an increase in the cross-link density in the low O-B samples followed by a decrease in samples at high filler content > 1 wt%.
The third part: (Study of Polyurethane/ODA-Bentonite Nanocomposites)
This part includes studying the properties of the polyurethane/ODA-Bentonite nanocomposites using different contents of ODA-B (from 0.25 – 5 wt %)
The morphology of the prepared samples were studied using X-ray diffraction and Transition Electron Microscope. As well as the thermal properties and electrical properties including (dc electrical conductivity and dielectric properties and their dependence on temperature) were studied.
The data refer to:
• The morphology structure of the samples implies that with a smaller content, the layered silicates of ODA-B were dispersed better and exfoliated by the polymer chains, but, as more ODA-B was added, not all the clay could be dispersed well enough. So that, it could be concluded that at high content of the ODA-B one area was mainly intercalated while the other are exfoliated by the polyurethane chains ( which is known as partially exfoliation).
• the thermal stability of these nanocomposites was significantly increased than the pristine PU.
• The current-voltage characteristics indicates the predominance of Pool-Frenckel conduction mechanism for all the nanocomposite samples and the blank one also.
• from the temperature dependence of the dc conductivity, it was found that Ea of the nanocompositesis less than that of neat PU, as well as it drops with the increase of the ODA-B content in the composites which indicate that the process of conduction becomes easier.
• Results confirm that the real part of complex dielectric function of the nanocomposites can be tailored by varying amount of ODA-B filler.