Poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)]/layered double hydroxide nanocomposites

BACKGROUND: The thermomechanical performance of poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] (PHBV) is associated with its crystallization. Enhanced nucleation using a stearate-functionalized synthetic layered double hydroxide (LDH) presents a potential solution. RESULTS: PHBV crystallization varied with concentration of LDH. At lower LDH concentration, thermal history-induced cold crystallization was present. The extent of this order-disorder transition decreased with increasing LDH concentration and was completely eliminated at 7 wt% LOH. PHBV did not have a melt recrystallization peak but the introduction of LDH resulted in an increasingly pronounced melt recrystallization with increasing LDH concentration. Polarized optical microscopy coupled with differential scanning calorimetry and wide angle X-ray diffraction (WAXD) analysis indicated increased lamella thickness in the nanocomposites compared to pure PHBV. WAXD and transmission electron microscopy showed that the nanocomposites had an intercalated but aggregated dispersion. CONCLUSION: The concentration of nanofiller provides unique effects in PHBV. Mechanical performance was found to scale with composition as determined using dynamic mechanical analysis and tensile testing. (C) 2008 Society of Chemical Industry58213314

Layer double hydroxides for enhanced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) crystallization

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 LauritzenHoffman 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. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 201312753395340