Effect of Irradiation on Some Mechanical and Physical Properties of Locally Produced Linear Low Density Polyethylene (LLDPE) and High Density Polyethylene (HDPE)

Abstract

The aim of the thesis is to study the effect different doses of X-ray radiation of 10 MeV energy on some mechanical and physical properties of the HDPE and LLDPE film samples. Chapter (I) is a general introduction on polymers; the molecular structure, classifications, nature, processing methods and applications of polymer and polyethylene grades, the ionization radiation definition, types, action with mater and radiation dose, types and relation between electromagnetic radiation and ionized radiation. Chapter (II) is concerned with the review of literature on different radiation doses and their effect on some mechanical and physical properties of polyethylene. The experimental work is given in Chapter (III). Preparation method used for preparing polyethylene thin film sheets and irradiation technique with different doses to the present study are studied. Tensile test was carried out and various mechanical parameters were calculated. The absorption spectra of the samples were measured using a spectrophotometer in wavelength range (200-900) nm. Recording infrared spectrophotometer in the wavelength range from (350-4000) nm was used. The differential thermal analysis scanning calorimeter was also used for measuring the thermal stability of the samples before and after irradiation. In chapter (IV), the results and discussion are given. The stress-strain curves for all samples were measured. From these curves, different mechanical parameters were calculated; namely, the yield strength, tensile strength, elongation at break and toughness. From calculation measurement it was found that the yield strength and tensile strength increases with increase radiation dose while the elongation at break and toughness decreases with increasing dose and this was explained due to the change in the molecular structure of polyethylene samples when exposed to X-ray radiation such as crosslinked or scission. From the optical absorption spectra, the electronic transition responsible for the absorption was found to be an allowed direct transition. The optical energy gap was calculated for each sample, it was found that the absorption curves show a sharply structured onset optical absorption attributed to exciton absorption. From the comparison of the infrared spectra revealed that the samples not significantly differ from each other. But it was noticed that the thermal analysis measurements indicated that the thermal stability is slightly affected by the variation of doses intensity.