Application of extrusion plastometry in poly(3-hydroxybutyrate) (PHB) processing and the effect of ground wool fiber on the mechanical properties of PHB/wool blends

Poly(3-hydroxybutyrate) (PHB) is a well-known member of the polyhydroxyalkanoate family of biopolymers and it has been extensively investigated as an environmentally-benign replacement for petrochemical-based polymers. The practical application of PHB in the biomedical field and in packaging has been limited because of its relatively narrow processing window, high brittleness, and low thermal stability. In this study, a melt flow extrusion plastometer was used to investigate the processability of PHB by evaluating its melt flow rate and the mechanical properties of its monofilament extrudates. The monofilament extrudates were collected after exposure to different processing temperatures (180°C and 190°C) and heating times as well as after blending the biopolymer with different fractions of ground raw wool. The melt flow rate of PHB was not significantly affected when blended with different amounts of wool fiber. However, the melt flow rate increased significantly with the increase in heat duration and temperature. The mechanical properties of the monofilament extrudates from the parental PHB and PHB/wool blends were influenced by the fraction of wool, temperature, and heat duration. The results of this study will be useful in selecting appropriate conditions to produce PHB-based blends/composites with desirable properties for a wide range of applications.