Preparation and properties of aligned poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites

In this study a unidirectionally aligned cellulose nanowhisker (CNW) composite was developed. CNW in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrix was aligned using an external electric field and the morphology and mechanical properties of the resultant anisotropic composites were studied. PHBV films with 1.5-7 wt% of CNWs were manufactured using solution casting. A DC electric field of 56.25 kV/m was applied during solvent evaporation. Both microstructural and mechanical analyses were performed to study the orientation of CNWs in the films. Mechanical properties of the samples were tested at 0°, 15°, 30°, 45° and 90° with respect to electric field direction by a dynamic mechanical analyzer (DMA). DMA results showed that CNW concentration has a strong influence on the degree of CNW alignment. The electric field was effective in aligning CNWs up to 4 wt% CNW concentration. The samples with higher concentrations showed virtually isotropic behavior, due to significantly enhanced restraints on CNW mobility. The restrains were attributed to CNW/CNW and CNW/polymer interactions. Rheological results confirmed the enhance restraints.