Fibrillar crystals of isotactic polystyrene. I. Morphological aspects |
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Authors: | A G Wikjord R St John Manley |
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Institution: | Department of Chemistry , Pulp and Paper Research Institute Mc Gill University , Montreal, Quebec, Canada |
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Abstract: | Fibrillar crystals have been prepared by the crystallization of isotactic polystyrene from stirred solutions in 1,3,5-trimethylben-zene and cyclohexanol. Similar microfibrils have been prepared in the nascent state by the polymerization of styrene in 1,3,5-trimethyl-benzene with a heterogeneous Ziegler-Natta catalyst. The microfibrils varied in width between 140 and 250 Å and were characterized by periodic lamellar overgrowths which were believed to give rise to a discrete X-ray reflection having a d-spacing of 90 A. Thermal analysis suggested that high growth temperatures favored greater crystal perfection. During crystallization from stirred cyclohexanol solutions, a fractionation of high molecular weight chains occurred which was more efficient at higher crystallization temperatures. In comparison to crystallizations under quiescent conditions, a marked facility of the crystallization process was observed in the formation of stirrer-crystallized and Ziegler-Natta polystyrene. The ease of crystallization of the shear-regenerated and nascent microfibrils has been related to a reduction in the free energy of nucleation. Mechanisms have been proposed to account for a favored nucleation process. |
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Keywords: | Poly (ethylene terephthalate) High-speed spinning Swelling Fibrillation Fiber x-ray diffraction |
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