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|Type:||Artigo de periódico|
|Title:||Layer Double Hydroxides For Enhanced Poly(3-hydroxybutyrate-co-3- Hydroxyvalerate) Crystallization|
|Abstract:||Enabling the widespread utilization of poly[(3-hydroxybutyrate)-co-(3- hydroxyvalerate)] (PHBV) is strongly associated with enhancing its crystallization kinetics. In this article, we utilize a highly surface active (one reactive group per nanometer square) anion exchanged layered-double hydroxide (LDH) functionalized by stearic acid to probe the crystallization kinetics of PHBV. Our prior work has shown that the addition of LDH decreases the cold crystallization and induces a melt recrystallization peak in PHBV. Since the melt-recrystallization temperature shifted to higher temperature and its corresponding enthalpy increased with increasing LDH loading, this article is focused on understanding the effect of LDH on kinetics and energetics of PHBV crystallization. Both Avrami and Lauritzen-Hoffman modeling are utilized to develop a comprehensive understanding of thermal history effects through differential scanning calorimetry and polarized optical microscopy measurements. Five concentrations by weight of LDH are used: 1, 3, 5, and 7%. The results show that the addition of LDH promoted both primary and secondary nucleation at low concentrations but additional LDH resulted in primary nucleation alone. The crystallization rate and activation energy show a significant increase, which is accompanied by a decrease in the nucleation constant, the surface energy and the work of chain folding for PHBV crystallization. Copyright © 2012 Wiley Periodicals, Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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