| Summary: | 碩士 === 元智大學 === 化學工程研究所 === 87 === First, we use differential scanning calorimeter (DSC) to analyze the crystallization and melting behavior of syndiotactic polystyrene (s-PS), then use small angle x-ray scattering (SAXS) and transmission electron microscope (TEM) to study the morphology of s-PS.
We use Hoffman-Weeks equation to analyze the data that obtained from DSC. For s-PS200K, the equilibrium temperature of a-form is 277.30oC, the equilibrium temperature of b-form is 291.21oC, and the equilibrium temperature is 286.49oC using the way of recrystallization. Similarly, for s-PS400K, the equilibrium temperature of a-form is 293.50oC, the equilibrium temperature of b-form is 293.21oC, and the equilibrium temperature is 289.35oC using the way of recrystallization. We know has something to do with temperature and time in the process of experiments. It is not a constant. So all equilibrium temperatures have to be revised.
In the experiments, we found the crystallization behavior for a-form and b-form structure of s-PS is different. a-form crystals are kinetically-favored structure, but b-form crystals are thermodynamically-favored structure. We discover only b-form structure which possesses a phenomenon of recrystallization.
Avrmai constant (n) is 3 and spherulites of hetergeneous nucleation are expected.
Prue a-form and b-form structure are obtained with different press conditions. Then we use fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffactometer (WAXD) to analyse structures.
In the morphology studies, we discover stacked lamellae when the isothermal temperature is below 265oC, and lamellae will be thickened when the isothermal temperature is increased. We can observe the single crystals when isothermal temperature is longer then 267oC. We can found those single crystals are almost a-form structure with the help of TEM.
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