Poly(vinylidene fluoride)-acrylic rubber partially miscible blends: Crystallization within conjugated phases induce dual lamellar crystalline structure

The miscibility of melt mixed poly(vinylidene fluoride)(PVDF)/acrylic rubber(ACM) blends and the crystal morphology of PVDF in the blends over the whole composition range were investigated by dynamic mechanical analysis (DMA), optical microscopy(OM), Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM). DMA analysis revealed that PVDF is partially miscible within the PVDF rich blends whereas it is fully miscible in the ACM rich blends. Phase diagram was obtained for alpha-PVDF/ACM blends using OM and DSC measurements. FTIR study showed that PVDF crystallizes in alpha form in the blends. Dendritic spherulites were observed for the miscible blends as well as for the ACM rich phase in partially miscible blends. Spherulite growth rate in miscible blends was analyzed by Lauritzen Hoffman equation. Blending with ACM increased free energy of folding for PVDF lamella. Lamellar thickness calculated for two conjugated phases in the partially miscible blends showed different values in agreement with the two peaks observed in SAXS profiles of partially miscible blends, suggesting dual lamellar crystal structure. (c) 2013 Elsevier Ltd. All rights reserved.