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Abstract Natural oils have attracted attention as raw materials for the preparation of natural biodegradable polymeric materials to replace the traditional petrochemical based polymers to be used for insulation purposes and ecological applications. Four chapters in addition to the summary in the english and arabic languages are included in the thesis. Chapter I comprises the introduction and the aim of work. A brief survey on the physical properties of vegetable oils and their applications are included. Some theories dealing with the experimental techniques in addition to some general aspects are given in chapter II. Materials under investigation and brief description of the apparatus used are given in chapter III. Results and discussion are given in chapter IV. Two maleated vegetable oils based on castor oil (COMA) and soybean oil (SOMA) in addition to aliphatic polyester based on propylene glycol and succinic acid (PPS) were prepared and characterized by means of infrared (IR), nuclear magnetic resonance (1H NMR) and thermo gravimetric analysis (TGA). SOMA was found to be more thermally stable than COMA and PPS. The dielectric permittivity ε’, dielectric loss ε” in addition to the electrical conductivity σ were studied over frequency range (0.1Hz to 5 MHz) showing an increase in the order COMA> SOMA> PPS. The moderate range of dc conductivity given for SOMA and PPS indicated that both materials could be used for antistatic applications while COMA is recommended to be used for electrostatic dissipation applications. The effect of different concentrations (1-5 wt %) of the prepared COMA, SOMA, and PPS on the hydrophysical properties of sandy soil was studied through total porosity, bulk density, field capacity, hydraulic conductivity, water holding capacity and water stability aggregates. Such properties are found to be improved by increasing the concentration, following the trend SOMA> PPS >COMA rather than the extraction of polycyclic aromatic hydrocarbons (PAH) from the soil to become suitable for plant growth. Blending is a useful technique to improve the physicomechanical properties of the polymers. Polymethyl methacrylate (PMMA) was selected to be blended with different compositions of COMA, SOMA, PPS to exhibit novel properties as well as biodegradability to be used for insulation purposes and medical applications. ε’ and ε” were found to increase by increasing the percentage of COMA, SOMA and PPS in the blend. The imaginary part of the electric modulus M” at the different frequencies was analysed using Havriliac –Negami function. The analysis of the data reveals three relaxation mechanisms relating to the conductivity relaxation, segmental and local molecular motions. The data given for the σdc indicated that the investigated blends are recommended to be used for antistatic applications. Moreover, it was noticed that the proportionality of σdc with the composition of the investigated blends is linear up till composition 70/30 wt %. This could be attributed to the miscibility of the investigated blends which is expected to be found only at that range of composition. This result is supported by the investigation carried out by SEM.The incorporation of the filler in the polymeric matrix exhibits remarkable improvement in its properties. Calcium carbonate (CaCO3) in the micro and nano scales was added in increasing quantities to PMMA/COMA, PMMA/SOMA and PMMA/PPS blends with composition 70/30 wt%. The prepared films were characterized through different techniques such as, thermo gravimetric analysis TGA, scanning electron microscope SEM, differential scanning calorimetry DSC, in addition to dielectric properties which were carried out at range of frequency from 0.1 Hz to 5 MHz and temperature range from 30 to 90 oC. Moreover the enzymatic degradation was carried out by immersing the prepared films in phosphate buffer solution. The data obtained for the three investigated systems indicate that: The dielectric permittivity ε’ and dielectric loss ε” increased by increasing either the concentration of the filler or the temperature. The analysis of the imaginary part of the electric modulus M″ which was carried out using Havriliak –Negami function revealed three relaxation mechanisms characterizing the conductivity relaxation, segmental molecular motion and the local motion of side groups attached to the main polymer chain. The values of τ1 and τ2 for the investigated systems at different concentrations of CaCO3 can be arranged in the following ascending order PMMA/COMA >PMMA/SOMA>PMMA/PPS while that for relaxation time τ3 follows the trend PMMA/SOMA> PMMA/PPS > PMMA/COMA. The decrease in the relaxations time τ1, τ2 and τ3 noticed by increasing temperature is started sharply up to (~ 60 oC) followed by a slight decrease. This could be attributed to cooperative reorientation motion of the polymeric segments as it is expected to take place at the glass transition.temperature. The slight decrease in τ1, τ2 and τ3 noticed above concentrations 30 and 10 wt % in case of micro and nano fillers could be attributed to the retardation of dipole matrix which become weak. On the other hand, the increase in τ3 noticed above both concentrations could be attributed to the stearic hindrance in the group mobility. According to Arrhenius equation, the two activation energies obtained through the glass transition temperature is considered to be a good support for change in molecular structure happened at such temperature. The data obtained for the electrical conductivity indicated that σdc is directly proportional with either the temperature or the filler content. The activation energy Eσ for the investigated systems shows knicks on the linear dependence of Arrhenius plots indicating that two activating energies below and above glass transition temperature are present. These values are found to follow the trend PMMA/SOMA> PMMA/PPS > PMMA/COMA.which is the opposite to the trend of σdc. Moreover, the data of σdc indicated that PMMA/COMA and PMMA/PPS are recommended to be used as antistatic materials when the concentration of both fillers in the matrix is less than 30 and 10 wt% and at temperature not exceed 60 oC where as at higher concentrations and temperatures, both blends are recommended to be used for electrostatic dissipation applications. On the other hand, it is interesting to notice that PMMA/SOMA blend at the different temperatures and filler concentrations is recommended to be used only in antistatic applications. The effect of different concentrations of CaCO3 in micro and nano scales on the enzymatic degradation of the investigated systems in phosphate buffer solution for 7 days was studied. The weight remaining was SUMMARY XV found to decrease with the increase in either the time of immersing or the concentration of the filler added. This was discussed in terms of the agglomeration which is expected to be found by increasing the filler content. This result is supported by investigation carried out by SEM. The easiest dispertion of the nano filler in the matrix is responsible for the decrease in the biodegradability when compared with that of the micro filler. |