Biodegradable fibers of poly(3-hydroxybutyrate) produced by high-speed melt spinning and spin drawing

The effects of high-speed melt spinning and spin drawing on the structure a nd resulting properties of bacterial generated poly(3-hydroxybutyrate) (PHB ) fibers were investigated. The fibers were characterized by their degree o f 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 (alpha modification) and hexago nal (beta modification) crystals, the latter as a result of stress-induced crystallization. The fiber structures formed during these processes were fi bril-like as the atomic force microscopy images demonstrated. The maximum p hysical 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%, res pectively. The fibers obtained by a low draw ratio of 4.0 had spherulitic s tructures and poor textile physical properties. The PHB pellets were analyz ed by their degradation during the processes of drying and spinning and by their thermal and rheological properties. (C) 2000 John Wiley & Sons, Inc.