| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 99 === We observe Syndiotactic Polystyrene (sPS) and Syndiotactic Polystyrene (sPP) by means of transmission electron microscope (TEM) and atomic force microscope (AFM). First, the samples are heating to above the melting point (Tm) to eliminate nuclei and cooling to suitable temperature for crystallization. The results of TEM indicate that sPS forms nanograins in early stage of melt crystallization at first. Its forms much more grains and aggregates as time of crystallization increasing. In thermodynamics, tiny grains have great surface energy, yet the aggregated grains cannot grow up individually. After many nanograins aggregate, a part of grains become liquid-like structure and adjust molecular chains to the same direction. Finally, liquid-like structure transforms into lamellae which is beta phase flat-on lamellae by [ool] zone electron diffraction pattern. Therefore, it does prove that beta phase flat-on lamellae forms at early stage of melt-crystallization.
Observing sample of sPS which crystallizes at 255 oC in 3 minutes by atomic force microscope (AFM), it forms multilayer flat-on lamellae and spiral lamellae. It not only corresponds with TEM experimental results, but also shows that it has lattice relationship between lamellae. Increasing time of crystallization to 5 and 10 minutes, we can observe liquid-like region forming.
Observing sample of Syndiotactic Polypropylene (sPP) which crystallizes at 100 oC in 3 minutes by AFM, it forms many nanograins. Increasing time of crystallization to 5 minutes, it forms nonograins and lamellae.
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