Article

Nucleation mechanism of polyhydroxybutyrate and poly (hydroxybutyrate-co-hydroxyhexanoate) crystallized by orotic acid as a nucleating agent

Journal of Applied Polymer Science (impact factor: 1.29). 01/2010; 115(2):709.
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    Dataset: The effect of nucleating agents on physical properties of poly-3- hydroxybutyrate (PHB) and poly-3-hydroxybutyrate-co-3- hydroxyvalerate (PHB-co-HV) produced by Burkholderia cepacia ATCC 17759
    Chengjun Zhu, Christopher T Nomura, Joseph A Perrotta, Arthur J Stipanovic, James P Nakas
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    ABSTRACT: a b s t r a c t In the absence of nucleating agents, polyhydroxyalkanoates (PHAs) generally exhibit slow crystallization rates which make them less favorable for injection molding purposes. The copolymer, PHB-co-HV (poly-3-hydroxybutyrate-co-3-hydroxyvalerate), exhibited increased T c as compared to the homopolymer PHB (poly-3-hydroxybutyrate). Increasing the mol fraction of HV monomer in the PHB-co-HV initially led to a decrease in the T m of the copolymer from 175.4 C to a minimum of 168.5 C, at 20 mol% of HV and, subse-quently, increased in PHB-co-HV copolymers with higher fractions of HV, indicating a typical isodimorphic relationship. Two nucleating agents, heptane dicarboxylic derivative HPN-68L and ULTRATALC Ò 609, were tested to increase the T c and reduce the time for crystallization necessary for injection molding. HPN-68L decreased the T decomp of the homopolymer and all copolymers by almost 50 C. However, the use of ULTRATALC Ò 609 as a nucleating agent slightly enhanced the T decomp and had negligible effect on the T m s of all polymers. Also, PHB and PHB-co-HV with 5% (w/w) talc exhibited higher T c than polymers without ULTRATALC Ò 609. A careful comparison of T c , T m and T decomp , for PHB-co-HV with 20 mol% of HV indicated that this copolymer is the best option for injection molding, with both a high T decomp and more rapid crystallization.
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