A synchrotron SAXS study of miscible blends of semicrystalline poly(vinylidenefluoride) and semicrystalline poly(1,4-butylene adipate). II. Crystallization, morphology, and PBA inclusion in PVF2 spherulites

摘要

The incorporation of poly(1,4-butylene adipate) (PBA) and its crystallization behavior within poly(vinylidenefluoride) (PVF2) spherulites in miscible PVF2/PBA blends have been further studied with small-angle X-ray synchrotron scattering (SAXS). The incorporation of PBA into the PVF2 interlamellar region was found to be dependent on the PVF2 crystallization conditions. In our previous work, where the blends were crystallized by a one-step quenching process directly from 190 (a single-phase region) to 20 degrees C (a three-phase region), the transition from PBA inclusion in the PVF2 interlamellar region to interlamellar exclusion occurred at a PBA weight fraction of similar to 0.5. In this case, where the blends were first quenched from 190 (a single-phase region) to 130 degrees C (a two-phase region) and then further quenched to 20 degrees C (a three-phase region), the transition occurred at a PBA weight fraction of less than 0.3. That is, when a blend is crystallized under different conditions, different amounts of the PBA component are incorporated into the PVF2 interlamellar phase. The thickness of the PVF2 interlamellar phase, in turn, may affect the PBA crystalline structure in the interlamellar region. Time-resolved SAXS was used to probe the crystallization dynamics of both PVF2 and PBA components in a blend containing 60 wt % PBA. The blend was quenched from the single-phase region at 190 to 130 degrees C to crystallize the PVF2 component and was then further quenched to 20 degrees C to crystallize the PBA component. This study, together with our earlier results, shows that the time dependence of the PVF2 crystallization rate and crystalline lamellar thickness is a function of the PBA content in the blend. The glass-transition temperature of the blend and the PBA diffusion process are the two dominant factors that control the PVF2 crystallization dynamics. (C) 2000 John Wiley & Sons, Inc. [References: 14]