Crystallization of poly(ε-caprolactone)/poly(vinyl chloride) miscible blends under strain:: The role of molecular weight

The effect of poly(epsilon-caprolactone) (PCL) molecular weight on the orientation of crystalline PCL in miscible poly(epsilon-caprolactoiie)/poly(vinyl chloride) (PCL/PVC) blends, melt crystallized under strain, has been studied by a combination of wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) studies. An unusual crystal orientation with the b-axis parallel to the stretching direction was observed in miscible PCL/PVC blends with PCL of high molecular weight (>21 000). SAXS showed the presence of nanosize confined PCL in the PCL/PVC blends, which could be preserved at temperatures higher than the T-m of PCL but lower than the T-g of PVC. A mechanism based on the confinement of PCL crystal growth was proposed, which can explain the formation of b-axis orientation in PCL/PVC blends crystallized under strain.