Journal
EUROPEAN POLYMER JOURNAL
Volume 37, Issue 8, Pages 1677-1684Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0014-3057(01)00034-9
Keywords
poly(3-hydroxybutyrate); semicrystalline morphology; dielectric relaxation; rigid amorphous phase
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The dielectric relaxation characteristics of poly(3-hydroxybutyrate) (PHB) in the glass-rubber (alpha) relaxation region has been investigated. A series of cold-crystallized samples were examined, with emphasis on the influence of semicrystalline morphology on relaxation properties. The presence of crystallinity had a marked impact on the alpha -relaxation characteristics of the various cold-crystallized specimens as compared to the wholly amorphous material. The constraining influence of the crystallites produced a progressive relaxation broadening and a positive offset in relaxation temperature. With regard to the dielectric relaxation strength, Delta epsilon, we found that the amorphous phase relaxation in the semicrystalline sample had a completely different temperature dependence compared to the wholly amorphous sample, leading to an increase in relaxation strength as the temperature increases above the glass transition temperature (T-g). This was explained by the existence of a rigid amorphous phase interface which relaxes gradually above the T-g of the mobile amorphous material. We suggest that the mobile material is essentially located in the amorphous gaps between lamellar stacks. (C) 2001 Elsevier Science Ltd. All rights reserved.
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