CRYSTALLIZATION BEHAVIOR AND ITS INFLUENCE ON THE MECHANICAL-PROPERTIES OF A THERMOPLASTIC ELASTOMER PRODUCED BY PSEUDOMONAS-OLEOVORANS

An investigation was conducted into the crystallization kinetics of PHO, poly(beta-hydroxyoctanoate), a bacterially produced copolyester containing mostly beta-hydroxyoctanoate repeating units. The crystallization rate reached a maximum at 0-5-degrees-C. The equilibrium melting point was determined to be approximately 68-degrees-C. The long-term crystallization study on PHO crystallized from the melt at -20,+5, and +20-degrees-C revealed that stable but different levels of crystallinity were reached after 3-7 weeks. The melting endotherm peak continued to change shape for up to 19 weeks. After 24 weeks of crystallization, the mechanical properties of the films were evaluated. The tensile modulus ranged from 2.5 to 9 MPa, the tensile strength at break from 6 to 10 MPa, and the ultimate elongation from 450% to 300%. A high tensile set, approximately 35% after 100% elongation, was observed for PHO crystallized at all three temperatures. Unusual melting endotherm peak shapes were observed for long-term crystallized samples after undergoing large extensions.