الفهرس 
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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
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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.