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Dielectric relaxation spectroscopy of poly[( R )‐3‐hydroxybutyrate] (PHB) during crystallization
Author(s) -
Bergmann Antje,
Owen Anthony
Publication year - 2004
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.1445
Subject(s) - spherulite (polymer physics) , crystallization , materials science , dielectric , relaxation (psychology) , amorphous solid , quenching (fluorescence) , glass transition , analytical chemistry (journal) , embrittlement , composite material , chemical engineering , crystallography , polymer , chemistry , organic chemistry , optics , fluorescence , psychology , social psychology , physics , optoelectronics , engineering
The dielectric response of poly [( R )‐3‐hydroxybutyrate] (PHB) was investigated as a function of time after quenching a film from the melt to a crystallization temperature of 20 °C. In the frequency range investigated (20 to 10 6 Hz) a relaxation maximum was observed–attributable to the glass transition–which could be analysed by the Havriliak–Negami relation. Changes in the complex dielectric constant were monitored both during spherulite growth (primary crystallization) and subsequently during a period of progressive crystallization (secondary crystallization) at room temperature. The relaxation strength changed only slightly during primary crystallization and its peak position remained at a constant frequency. Subsequently a continuous decrease in relaxation strength occurred, indicating considerable changes in molecular mobility after spherulite growth had been completed. The results provide further evidence that molecular mobility in the amorphous regions decreases significantly with time, and that this would be the reason why PHB shows embrittlement on ageing at room temperature. Copyright © 2004 Society of Chemical Industry