The Effect of Poly(Butylene Adipate-co-Terephthalate) on Crystallization Behavior and Morphology of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)

Abstract

The effects of poly(butylene adipate-co-terephthalate) (PBAT) on crystallization behavior and morphology of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied to provide the useful information to control and improve PHBV processing. PHBV were blended with 15, 30 and 50 wt% PBAT by twin screw extrusion and these were subsequently compared to unblended PHBV. The rate of crystal development determined from differential scanning calorimetry (DSC) at 120 °C showed that the incorporation of PBAT retarded the crystal growth rate. Moreover, the crystal structure of polymer blends was examined by X-ray diffraction (XRD) and the results revealed that PBAT did not affect the crystal structure of PHBV. The responses of the melt-crystallized PHBV to different quantities of PBAT were recorded by polarized optical microscopy (POM). The results demonstrated that the size of spherulite dramatically increased when 15 wt% PBAT was added and the shape of spherulite was imperfect when PBAT reached 30 wt%. The morphologies of PHBV and its blends on the freeze-fractured specimens were exposed using scanning electron microscopy (SEM). The SEM images revealed the phase separation of PHBV/ PBAT blends in any composition. The morphology of 15 and 30 wt% PBAT presented droplet in matrix morphology and changed to co-continuous morphology at 50 wt% PBAT.