| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 99 === The melt crystallization process of two classical crystallized polymer (polyethylene and syndiotactic polystyrene) is to be examined by means of TEM and AFM for this study. There are considerable amount of nanograins formed at the beginning, and they can be mainly divided into two categories, which are the disc-like ones and the tower-like ones. The polymer chains of the disc-like ones would be perpendicular or parallel to the sample surface, with height of less than 20 nm. However, these nanograins might coalesce at the initial phase of crystallization because of a high density of nucleation, resulting in the polymer chains’ random arrangement of worm-like nanograins. The entire polymer chains of the tower-like nanograins are parallel to the sample surface yet developed perpendicularly. There are three primary polymer crystallization mechanisms having been proposed in the literature: 1. A hexagonal mesophase developed from the outset of the crystalline phase proposed by Stephen Z. D. Cheng and Lotz. 2. That a mesomorphic layer being absorbed at first, then thickening and turning into a constant arranged granular crystal layer, finally into homogeneous lamellar crystallines proposed by Strobl. 3. That the lamellar were coalesced by nanograins proposed by Jeng U. et al. However, based on our experiments, nanograins would be melting into a state of fusion and connecting each other at the early stage of melt crystallization instead of growing and coalescing into lamellae. We found that here were great amount of nanograins formation at the initial stage, the nanograins then coalesced and melted into the fusion mesophase which was amorphous. In the last stage the fusion droplets were solidified and transformed into a large scale of lamella. Thus, a newly discovered crystallization mechanism will thus be proposed, developed and illustrated further in this study.
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