DYNAMICS OF POLY(VINYL BUTYRAL) STUDIED BY DIELECTRIC SPECTROSCOPY AND 1H NMR RELAXOMETRY
| Autor: | Silvia Pizzanelli, Daniele Prevosto, Massimiliano Labardi, Tommaso Guazzini, Simona Bronco, Claudia Forte, Lucia Calucci |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | XLVI national Congress on Magnetic Resonance, Fisciano (Salerno), 27-29/09/2017 info:cnr-pdr/source/autori:Silvia Pizzanelli, Daniele Prevosto, Massimiliano Labardi, Tommaso Guazzini, Simona Bronco, Claudia Forte, Lucia Calucci/congresso_nome:XLVI national Congress on Magnetic Resonance/congresso_luogo:Fisciano (Salerno)/congresso_data:27-29%2F09%2F2017/anno:2017/pagina_da:/pagina_a:/intervallo_pagine |
| Popis: | The combined use of Dielectric Spectroscopy (DS) and 1H Fast Field-Cycling (FFC) NMR relaxometry allowed a detailed understanding of the dynamic behavior of the amorphous ter-polymer poly(vinyl butyral) (PVB) to be achieved across the glass transition temperature (Tg=70 °C by Differential Scanning Calorimetry). Above Tg, main chain segmental motions (alpha relaxation) were detected and characterized by both DS and FFC NMR relaxometry. The alpha process showed a Vogel Fulcher Tammann temperature dependence, with an associated Tg of 69 °C and a fragility of 155 for PVB glass. Below Tg, DS revealed a beta relaxation ascribed to reorientations of the vinyl alcohol dipoles due to local twisting motions and allowed an activation barrier of 11 kcal/mol to be determined. NMR relaxometry data supported the occurrence of this motion, although 1H relaxation could also be affected by reorientations of propyl side chains. |
| Databáze: | OpenAIRE |
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