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

The incorporation of poly(1,4-butylene adipate) (PBA) and its crystallizati on behavior within poly(vinylidenefluoride) (PVF2) spherulites in miscible PVF2/PBA blends have been further studied with small-angle X-ray synchrotro n scattering (SAXS). The incorporation of PBA into the PVF2 interlamellar r egion was found to be dependent on the PVF2 crystallization conditions. In our previous work, where the blends were crystallized by a one-step quenchi ng process directly from 190 (a single-phase region) to 20 degrees C (a thr ee-phase region), the transition from PBA inclusion in the PVF2 interlamell ar region to interlamellar exclusion occurred at a PBA weight fraction of s imilar 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 furt her quenched to 20 degrees C (a three-phase region), the transition occurre d at a PBA weight fraction of less than 0.3. That is, when a blend is cryst allized under different conditions, different amounts of the PBA component are incorporated into the PVF2 interlamellar phase. The thickness of the PV F2 interlamellar phase, in turn, may affect the PBA crystalline structure i n the interlamellar region. Time-resolved SAXS was used to probe the crysta llization 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 13 0 degrees C to crystallize the PVF2 component and was then further quenched to 20 degrees C to crystallize the PBA component. This study, together wit h our earlier results, shows that the time dependence of the PVF2 crystalli zation rate and crystalline lamellar thickness is a function of the PBA con tent in the blend. The glass-transition temperature of the blend and the PB A diffusion process are the two dominant factors that control the PVF2 crys tallization dynamics. (C) 2000 John Wiley & Sons, Inc.