Development and Characterization of Poly(butylene succinate-co-adipate)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Cowpea Lignocellulosic Fibers as a Filler via Injection Molding and Extrusion Film-Casting

Biodegradable poly(butylene succinate-co-adipate)/Poly(3-hydroxybutyrate-co-3-hydoxyvalerate) (PBSA/PHBV) filled with lignocellulosic sidestream/fibers from cowpea, a neglected and underutilized African crop are produced by injection molding and extrusion film casting. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) suggests that the fibers have more affinity and interfacial interaction with PBSA than PHBV. This is shown by a decrease in dampening of PBSA and an increase in dampening of PHBV with fiber addition. In addition, fiber addition results in more homogeneous crystal morphology of PBSA, while resulting in more heterogeneous crystal morphology of PHBV. The tensile strength of injection molded bio-composites increases with fiber addition due to good interfacial adhesion between the matrix and fibers revealed by scanning electron microscope. In contrast, the tensile strength of bio-composite films decreases with fiber addition due to the high-volume fraction of pores in bio-composite films that act as stress raisers. The stiffness of both injection molded, and bio-composite films increase with fiber addition, as revealed by an increase in Young's modulus and storage modulus, while the tensile strain decreases. In conclusion, low-value cowpea sidestream can be used as a filler to produce injection molded bio-composites and bio-composite films for potential application as rigid and flexible packaging.