الفهرس 
Introduction and literature surveyOnly 14 pages are availabe for public view
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Abstract
Blends of LDPE/wax in ratios of 100/0, 98/2, 96/4, 94/6, 92/8, 90/10 and 85/15 (w/w) were prepared by melt-mixing at the temperature of 150°C. It was found that increasing the wax content more than 15% leads to phase separation.
Surface morphology, structure, and mechanical properties of low density polyethylene (LDPE) /paraffin wax blends were studied for both un-irradiated and irradiated samples by using scanning electron microscope (SEM), X-ray diffraction (XRD), and mechanical tests. The lattice parameters which include crystal size, dislocation density, interchain distance, interplanner distance, micro stain, and distortion parameters were calculated. Both The blending and gamma irradiation process has an influence on the structure and consequently on the surface morphology of the samples. The values of lattice parameters were calculated. The grain size, inter chain distance and inter-planar spacing decrease with increasing paraffin and increase with increasing gamma irradiation doses. While the dislocation density, the micro-strain and the distortion parameters increase with increasing paraffin wax ratio and decreases with increasing gamma irradiationdoses. The obtained values from X-ray indicates that notable changes of the atomic lattice structure for both unirradiated and irradiated blends, which also confirmed by studying the surface morphology of all blends.
Mechanical properties such as tensile strength, elongation at break, Young modulus, and hardness, were investigated and compared with those of irradiated samples. It was found that an increase in wax content induces a linear decrease in tensile strength; elongation at break, young’s modulus, and hardness. A linear increase of these mechanical parameters was observed with increasing different gamma irradiation doses. The final results show the reliability of gamma radiation as a practical method for the control of long-term properties. Correlation between the mechanical properties and structural parameters of the blend samples were observed
The thermal properties of low-density polyethylene (LDPE)/paraffin
wax blends were studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and melt flow index (MFI). DSC results showed that for all blends both the melting temperature (Tm) and the melting enthalpy (Hm) decrease linearly with an increase in wax content. TGA analysis showed that the thermal stability of all blends decreases linearly with increasing wax content. No clear correlation was observed between the melting point and thermal stability. Horowitz and Metzger method was used to determine the thermal activation energy (Ea). MFI increased exponentially by increasing the wax content. The effect of gamma irradiation on the thermal behavior of the blends was also investigated at different gamma irradiation doses. Significant correlations were found between the thermal parameters (Tm, Hm, T5%, Ea and MFI) and the amount of wax content and gamma irradiation.
Optical and electrical properties of pure samples and LDPE/paraffin wax blend samples were studied before and after gamma irradiation. The optical band gap ( ) and Urbacht energy (EU) in the LDPE/paraffin wax blend samples were determined. The results show a decrease in and increase in EU by increasing paraffin wax ratio (up to 15%) in the LDPE, and the transition energy for electrons is an allowed indirect. The electrical properties include dielectric constant (ε’), dielectric loss (ε’’) and the ac conductivity (σac) in the frequency range (50 KHz - 1 MHz) at room temperature were investigated. ε’, ε’’ and σac increase with increasing paraffin wax ratio. ε’ and ε’’ values is higher at low frequencies while, at high Frequencies the trend is reversed.
Influence of gamma radiation on the optical and electrical properties for the pure samples and LDPE/paraffin wax blends at different gamma irradiation doses has been evaluated. decreases, while EU increases with increasing irradiation dose. Also, ε’, ε’’ and σac increase with increasing irradiation dose. The results of the optical and electrical characteristics indicate a relation between the amorphous nature of the samples and its electrical conductivity.