| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 5206757 | Polymer Testing | 2012 | 7 Pages |
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 Tc 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 Tm of the copolymer from 175.4 °C to a minimum of 168.5 °C, at 20 mol% of HV and, subsequently, 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®609, were tested to increase the Tc and reduce the time for crystallization necessary for injection molding. HPN-68L decreased the Tdecomp of the homopolymer and all copolymers by almost 50 °C. However, the use of ULTRATALC®609 as a nucleating agent slightly enhanced the Tdecomp and had negligible effect on the Tms of all polymers. Also, PHB and PHB-co-HV with 5% (w/w) talc exhibited higher Tc than polymers without ULTRATALC®609. A careful comparison of Tc, Tm and Tdecomp, for PHB-co-HV with 20 mol% of HV indicated that this copolymer is the best option for injection molding, with both a high Tdecomp and more rapid crystallization.
