Biophysical Properties of Prepared Polyesters Based on Some Vegetable Oils

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.