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Authors
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Chang, B. ; Schneider, K. ; Vogel, R. ; Heinrich, G.
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Title
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Influence of annealing on mechanical ac-relaxation of isotactic polypropylene: A study from the intermediate phase perspective
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Date
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01.11.2017
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Number
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54273
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Abstract
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The influence of annealing on mechanical ac-relaxation of isotactic polypropylene (iPP) is investigated. In the sample without annealing, polymer chains in the intermediate phase are constrained by crystallites with a broad size distribution, leading to one ac-relaxation peak with activation energy (Ea) of 53.39 kJ mol-1. With an annealing temperature between 60 and 105 °C imperfect lamellae melting releases a part of the constraining force. Consequently, two ac-relaxation peaks can be observed (ac1- and ac2-relaxation in the order of increasing temperature). Both relaxation peaks shift to higher temperatures as annealing temperature increases. Ea of ac1-relaxation decreases from 38.43 to 35.55 kJ mol-1 as the intermediate phase thickness increases from 2.0 to 2.2 nm. With an annealing temperature higher than 105 °C, a new crystalline phase is formed, which enhances the constraining force on the polymer chains. So the ac1-relaxation peak is broadened and its position shifts to a higher temperature. Moreover, the polymer chains between the initial and the newly formed crystalline phase are strongly confined. Therefore, the ac2-relaxation is undetectable. Ea of ac1-relaxation decreases from 23.58 to 13.68 kJ mol-1 as the intermediate phase thickness increases from 2.3 to 3.0 nm.
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Publisher
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Macromolecular Materials and Engineering
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Wikidata
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Citation
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Macromolecular Materials and Engineering 302 (2017) ID1700291
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DOI
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https://doi.org/10.1002/mame.201700291
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Tags
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