The effects of high‐speed melt spinning and spin drawing on the structure and resulting properties of bacterial generated poly(3‐hydroxybutyrate) (PHB) fibers were investigated. The fibers were characterized by their degree of crystallinity by differential scanning calorimetry (DSC) and wide‐angle X‐ray scattering (WAXS), their orientation by WAXS, and the textile physical properties. The WAXS studies revealed that the fibers spun at high speeds and high draw ratios possessed orthorhombic (α modification) and hexagonal (β modification) crystals, the latter as a result of stress‐induced crystallization. The fiber structures formed during these processes were fibril‐like as the atomic force microscopy images demonstrated. The maximum physical break stress, the modulus, and the elongation at break observed in the fibril‐like spin drawn fibers were about 330 MPa, 7.7 GPa, and 37%, respectively. The fibers obtained by a low draw ratio of 4.0 had spherulitic structures and poor textile physical properties. The PHB pellets were analyzed by their degradation during the processes of drying and spinning and by their thermal and rheological properties. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2841–2850, 2000

A process for the large-scale production of 4-hydroxyvalerate (4HV)-containing biopolyesters with a new monomer composition was developed by means of high-cell-density cultivation applying recombinant strains of Pseudomonas putida and Ralstonia eutropha, harboring the PHA-biosynthesis genes phaC and phaE of Thiocapsa pfennigii. Cell densities of about 20 g/L revealing a PHA content of 52% (w/w) and a molar fraction of 4HV of up to 15.4 mol % were obtained by a two-stage fed-batch cultivation process at a 25-L scale using octanoic acid during the growth phase and levulinic acid for the accumulation of 4HV-containing polyesters. Besides 4HV the polyester contained significant amounts of both 3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV) and traces of 3-hydroxyhexanoic acid (3HHx) and 3-hydroxyoctanoic acid (3HO). With glucose or gluconic acid as the growth substrate, the components of the polyester could be reduced to mainly 3HV and 4HV with only a negligible fraction of 3HB, resulting in a polyester with a new composition. Scale-up of the cultivation process to a 500-L scale was successfully performed, resulting in the production of these polyesters at a pilot plant scale. Short-term shifts in temperature and pH resulted in the formation of cell agglomerates of about 50-100 microm by which the effectiveness of the semicontinuous centrifugation process was drastically increased. Washing of the freeze-dried cells with boiling methanol significantly shortened the extraction process and resulted in a polyester of higher purity. The physical and mechanical properties of these copolyesters were characterized by means of size exclusion chromatography, dynamic mechanical analysis, differential scanning calorimetry, stress-strain measurements, and measurements of the viscosity of the solution. The copolyesters were cast into films, spun to fibers, or processed into test bars by melt spinning and injection molding, respectively. They revealed an almost entirely amorphous structure and consequently were sticky and lacked strength. However they showed high thermal stability and an unusually high elongation at break of about 200%; the molecular weights (M(w)) were between 2.0 x 10(5) and 3.3 x 10(5) g/mol. It was shown that 4HV-containing polyesters belong to the class of thermoplastic elastomeres.

This paper reports on an attempt to use CD and CD/PHB ICs as nucleation agents for PHB in a high-speed melt spinning process. At first rheological and thermal properties of the nucleated melts are determined in order to assess the influence of the nucleating agents. Then spinning tests are carried out. Thermal and textile properties of the spun PHB fibers are also determined. An estimation of the improvement of inhibition of the secondary crystallization from use of the described blood compatible nucleating agents is given.

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Five kinds of polylactides (PLAs), with different d-lactide contents and tacticities, were subjected to high-speed melt-spinning experiments. In addition to stereochemical purity, the PLA types differed in molecular mass and molecular mass distribution. The properties of the different PLA materials were characterized by thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis, size exclusion chromatography, and 1 H-NMR and 13 C-NMR spectroscopy. The material was spun with a highspeed spinning process within the range 2000 -5000 m/min. The physical and tensile properties of the fibers were determined. The maximum tensile properties of the fibers were a 300 MPa tenacity at an elongation at break of 30% and a tensile modulus of 6.8 GPa.