Crystallization kinetics of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/cellulose nanowhiskers composites

In this study, biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films with 1.2-4.6 wt% of cellulose nanowhiskers (CNWs) were manufactured by solution casting using N,N-dimethylformide (DMF) as the solvent. Crystallization behaviors of PHBV/CNW composites were studied under isothermal conditions using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The changes in PHBV crystalline structure were studied using wide angle X-ray diffraction (WAXD). Avrami analysis was performed to study the effects of CNW concentration and temperature on the crystallization rate and crystallinity of PHBV. POM study confirmed the results from the Avrami analysis. In particular, the results revealed the dual effects (i.e., nucleation and confinement) of CNWs on PHBV nucleation. Depending on the concentration of CNWs, the crystallization rate of PHBV could be either increased or decreased due to the combined effects. High crystallization temperatures increased the diffusion rate of PHBV chains and the growth rate of PHBV spherulites. However, the nucleation effect of CNWs decreased at high crystallization temperatures.