PHASE-SEPARATION IN BLENDS OF OLIGO(CAPROLACTONE GLYCOL) BASED POLYURETHANE WITH POLYVINYL-CHLORIDE)

The structure of oligo(caprolactone glycol)-based polyurethane-poly(vinyl chloride) (PVC) blends obtained from tetrahydrofuran solution was studied by X-ray diffraction and electron microscopy. The system is characterized by a complex phase diagram with two types of equilibria: (1) crystal-liquid equilibrium in the region of blend compositions up to 40 wt% PVC; (2) liquid-liquid equilibrium in the region of mean compositions. The crystallization kinetics of oligo(caprolactone) polyurethane blocks from an initially compatible amorphous blend was investigated. Small-angle X-ray scattering (SAXS) studies provide evidence that the amorphous component (PVC) is incorporated in the interlamellar crystalline regions of the compositions. The amorphous blends are characterized by the presence of modulated structures at two scale levels, this being explained as a result of the process in which the bulk samples were obtained from a three-component polymer-polymer-solvent system.