Morphology and structure of poly(p-phenylene terephthalamide) crystallized from dilute organic solution |
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Authors: | Catheryn L Jackson Henri D Chanzy |
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Affiliation: | E. I. Du Pont de Nemours and Company, Experimental Station, Central Research and Development, Wilmington, DE 19880-0356, USA Centre de Recherches sur les Macromolécules Végétales CNRS, BP 53X-38041, Grenoble Cedex, France |
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Abstract: | The high-temperature crystallization of poly(p-phenylene terephthalamide) (PPTA) from dilute organic solutions was achieved through the introduction of a non-solvent, or precipitating agent, at the desired crystallization temperature. The morphology and crystal structure were examined for crystals produced from PPTA polymer with two different molecular weights (Mw = 46000 and 3430 g mol?1), using transmission electron microscopy. For the high-molecular-weight polymer, ribbon-like crystals were produced, while the low-molecular-weight polymer yielded small needles or platelets. In both cases, electron diffraction showed that the Northolt allomorph was obtained. For the high-molecular-weight polymer, the molecular axes were parallel to the ribbon axes in a chain-extended type structure. A hypothesis for the orientation of the low-molecular-weight PPTA in the small platelets, is also given. |
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Keywords: | poly(p-phenylene terephthalamide) solution crystallization morphology |
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