Fibers from Polyhdroxyalkanoates and Its Derivatives and Blends
Polyhydroxyalkonates are a diverse family of biopolyester produced by bacteria as energy and carbon storage materials. Poly(3-hydroxybutyrate) (PHB) is the most common type of PHA used commercially. PHB is an thermoplastic material with a melting temperature of about 180 °C and glass temperature that is below room temperature. Structure and properties of PHB are highly dependent on the conditions prevailing during fiber production. For instance, slow cooling from the melt produced large spherulites and rapid cooling results in amorphous state [01Yam]. It was suggested that PHB assumed orthorhombic or α-form or the β-zigzag form depending on the annealing conditions. PHB crystallized into orthorhombic form when annealed under high tension and into β-zigzag form when annealed under high tension [01Yam]. Based on X-ray diffraction patterns, it was found that the amorphous molecules transformed into orthorhombic crystal when annealed without tension and when annealed under tension, the amorphous regions were stretched and crystallized into the β-form [01Yam].