Abstract:
This thesis describes the effects of 60Co gamma radiation and solar radiation on Polyethylene (PE) and Polyvinyl chloride (PVC) materials manufactured by GIAD Industrial Company in Khartoum, Sudan. Both the PE and PVC materials were irradiated by direct solar radiation in air for different periods of time. Then the PE and PVC materials were irradiated by gamma radiation using 60Co source at doses in range of 10 to 108 KGy. The mechanical, thermal and electrical properties of irradiated and non-irradiated PE and PVC materials were studied. Obtained results showed that increasing the total irradiation dose and exposure time of gamma rays and solar radiation, results in increasing the tensile strength for all samples except black PVC sample, where it decreases. Similarly the strength of grain (Distension) and elongation at break increased by increasing the radiation dose and exposure time for both source of radiation for all PE and PVC samples. Generally there was improvement in the mechanical properties of PE and PVC samples after their irradiation by gamma rays as well as by solar radiation, including samples of black PVC. Although the irradiation by gamma rays and solar radiation affected the thermal conductivity and thermal resistance the changes imparted were not systematic. However the effect of gamma rays positively improved the thermal resistance of both samples of PE and PVC, while solar radiation had imparted a negative effect on the polymers. Exposure of PE and PVC to gamma radiation also resulted in decreasing the permittivity and increasing the dielectric constant hence improving isolation properties of the polymer. While irradiation of PE and PVC with solar radiation deteriorated the isolation properties of the polymer samples by increasing the permittivity and decreasing the dielectric constant. Generally there was a curing effect due exposure to gamma radiation while there was degradative effect due to exposure to solar radiation. The change in mechanical and electrical properties exhibited by PE and PVC samples exposed to gamma radiation was linear permitting the measurement of the gamma rays total exposure dose by correlating the amount of change in the mechanical or electrical property to gamma rays total exposure dose. Consequently such a system may be utilized as a dosimeter. Also the change in PE and PVC mechanical,
