A new crystal morphology of straight-stalk dendrites in blends of poly(butylene adipate) with amorphous poly(vinyl acetate)

Discontinuity in crystallization rates and a new and unusual morphology consisting of thickened straight-stalks crystal lamellae with also straight branches radiating out from a common nucleus were observed in blends of poly(vinyl acetate) (PVAc) with poly(1,4-butylene adipate) (PBA). The discontinuity in the crystal growth and mechanisms of straight-dendrite morphology of the PVAc/PBA blends were analyzed using polarized-light optical microscopy (POM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD). The discontinuity in crystallization rate and dendritic morphology occurred only at or near PVAc/PBA 10/90 blend composition upon crystallization at high-temperature regimes of Tc = 30–33 °C. By comparison, when crystallized at the same temperatures, PVAc/PBA blends of amorphous polymer loading greater than 15% or the neat PBA (amorphous polymer loading = 0) developed no dendrites but only typical Maltese-cross spherulites. Mechanism of straight dendrites in the blends is preliminarily expounded. Detailed interpretation requires further analyses.