Effect of poly(butylene succinate) on the morphology evolution of poly(vinylidene fluoride) in their blends

The effect of PBS on the morphological features of PVDF has been investigated by optical and atomic force microscopies under various conditions. It was found that neat PVDF forms large γ form spherulites with extraordinarily weak birefringence at 170°C. Adding 30% PBS makes PVDF exhibit intrigued flower-like spherulitic morphology. The growth mechanism was explained by the decrease of the supercooling and the materials dissipation. Increasing the PBS content to 70% favors the formation of ring banded spherulites. Temperature dependent experiments verify the γ→γ phase transition occurs from the junction sites of the α and γ crystals, while starts from the centers of α spherulites in the blends. Ring banded structures could be observed in neat PVDF, 70/30 blend and 30/70 blend when crystallized at 155°C, without γ crystals. The band period of PVDF α spherulites increases with crystallization temperature as well as the amount of PBS content. At 140°C, spherulites in neat PVDF lose their ring banded feature, while coarse spherulites consisting of evident lamellar bundles could be found in 30/70 blend.