STRUCTURAL-ANALYSIS OF POLY(3-HYDROXYBUTYRATE-CO-3-HYDROXYVALERATE) FIBERS PREPARED BY DRAWING AND ANNEALING PROCESSES

Structure of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepa red by drawing and annealing processes has been analyzed through wide- angle X-ray diffraction (WAXD), density, infrared dichroism, and biref ringence measurements. There are three different types of crystalline structure in these fibers: two of these are the two types of orthorhom bic with different orientation modes (the ordinary c-axis orientation (c parallel to Z), and the preferential orientation of c-axis to the d irection perpendicular to the fiber axis (c perpendicular to Z)); and the third is pseudohexagonal. The weight fractions of the three types of crystals and amorphous phase were analyzed combining the WAXD integ rated intensity and density data. The relation between crystalline ori entation factors obtained separately from the WAXD measurement and the infrared dichroic ratio is also discussed. The birefringence of these fibers shows negative and positive values, depending on drawing and a nnealing temperatures. Considering the intrinsic birefringence and wei ght fraction of the c parallel to Z, c perpendicular to Z, and pseudoh exagonal crystals, birefringence of the amorphous phase was evaluated. The amorphous birefringence shows positive values and decreases with an increase in the annealing temperature. From the analyzed fiber stru cture, it was speculated that the c perpendicular to Z and pseudohexag onal crystals are preferentially formed in the drawing process irrespe ctive of the drawing temperature. (C) 1998 John Wiley & Sons, Inc.