Recognition of the syndiotactic polypropylene polymorphs via dynamic-mechanical analysis |
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Authors: | Giuliana Gorrasi Liberata Guadagno Concetta D'Aniello Carlo Naddeo Gennaro Romano Vittoria Vittoria |
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Affiliation: | 1. Dipartimento di Ingegneria Chimica e Alimentare - Università di Salerno Via Ponte Don Melillo 84084 Fisciano Salerno, Italy;2. Istituto di Chimica e Tecnologia dei Polimeri - CNR Via CampiFlegrei, 34 80078-Pozzuoli, Napoli, Italy |
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Abstract: | Three syndiotactic polypropylene samples were crystallized under different conditions in order to obtain different polymorphs. A first sample was crystallized at high temperature, obtaining the helical form I; a second was crystallized from the melt at 0°C for many days obtaining the trans-planar mesophase; a third sample was obtained by solvent induced crystallization followed by annaeling of the trans-planar mesophase, leading to a mixture of both the helical forms I and II. In the dynamic-mechanical analysis the helical form I showed only one peak of tan δ corresponding to the amorphous glass transition. The other polymorphs also showed this transition centered at about the same temperature. Beside the peak corresponding to the Tg, the trans-planar mesophase was characterized by a peak appearing at 70°C, and the helical form II by a peak at 100°C. These peaks, unambiguously associated to transitions of the different forms, can be considered a distinctive evidence for the polymorphs obtained in different processing conditions. |
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Keywords: | polymorphism polypropylene syndiotactic trans-planar mesophase |
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