Phase Behavior and Its Effects on Crystallization in a Poly(trimethylene terephthalate)/Phenoxy Resin Blend
Phase behavior and its effects on crystallization in an extruded poly(trimethylene terephthalate) (PTT)/phenoxy resin blend were studied with time-resolved light scattering (TRLS), optical microscopy (OM), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS). During annealing in the molten state, a two-phase structure with unique periodicity and phase connectivity was developed by liquid–liquid phase separation. After the formation of the phase-separated structure, the blend was homogenized by the interchange reactions between the two polymers. The crystallization behavior of PTT predominantly depended on the phase morphology developed during annealing. The pre-existing phase structures disturbed the lamellar orientation, resulting in a poorly ordered spherulitic superstructure.
Crystallization of Poly(ε-caprolactone) in Poly(vinylidene fluoride)/Poly(ε-caprolactone) Blend
The crystallization behavior of poly(ε-caprolactone) (PCL) in a poly(vinylidene fluoride) (PVDF)/PCL blend as well as on a highly orientated PVDF substrate was studied by means of POM, DSC and TEM. The results show that the miscibility of the PVDF/PCL blend and the spherulitic morphology of PVDF varies with the blend ratio. For all the compositions, the pre-existing PVDF crystals accelerated the crystallization of PCL because the PVDF exhibits very strong nucleation ability toward PCL as reflected by the occurrence of heteroepitaxy and the transcrystallization of PBA on the PVDF substrate. This is associated with the perfect lattice matching between the PBA and PVDF crystals.
Nonequilibrium liquid-liquid phase separation in crystallizable polymer solutions
The relation between liquid-liquid phase separation and crystallization was investigated by applying a systematic change in the interaction in isotactic polypropylene (i-PP) solutions with a proper selection of solvents. A series of dialkyl phthalates, with a different number of carbon atoms in the alkyl chain, was usded to control the solvent quality. The liquid-liquid phase separation temperature decreased remarkably when the interaction became favorable while the melting point curve remained constant. As the result of this systematic change in polymer-solvent interaction, the liquid-liquid phase separation was observed under nonequilibrium conditions below the equilibrium liquid-solid transition