| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 101 === After Co60 gamma-ray irradiation, the polymer materials will change their mechanical, optical, thermal, and chemical properties. Then this thesis focuses on the evolution of hardness and chemical reactions at elevated temperature. The hardness of polymer is controlled by the defect induced by the gamma-ray irradiation, and the irradiated polymer also generates free radicals since the high-energy particles break the chemical bond of the polymer.
In this experiment, the polyoxymethylene (POM) specimen was irradiated by Co60 gamma-ray. The study is divided into two parts, one is the evolution of hardness during different annealing temperatures, and the other is the Electron Paramagnetic Resonance (EPR) spectra using computer software WINEPR, SimFornia and WinSim2002.
We found the hardness of irradiated polyoxymethylene increases with annealing time. The hardness reduces when gamma-ray dose increases. The annealing of defects which affect the hardness follows a mixture of zeroth order and first order kinetic processes. The EPR spectra of irradiated POM are possibly attributed to four radicals, which are ˗OCH2• as radical Ra, ˗OĊHO˗ as radical Rb, ˗CH2O• as radical Rc and HOO• as radical Rd, respectively. Electron Paramagnetic Resonance spectra decrease with increasing time and the intensity increases when gamma-ray dose rises.
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