Effect of acrylonitrile content of SAN on the bending morphology and its quantitative variation inside crystals of PCL/SAN blends confined in thin films

The effect of acrylonitrile content of SAN on the bending morphology of PCL/SAN blends was studied. The blends were prepared from solution with different compositions, and isothermally crystallized at a certain temperature. During crystallization at 45°C, the truncated lozenge-shaped morphology of the PCL crystals being modified to regular/inverted S- or C-shaped morphology for PCL/SAN blends with 9.5–25% AN in SAN. The bending curvature increases by lowering the crystallization temperature, and the growth rate of PCL decreases with SAN reflecting the miscible nature of the blends. For blends with 30% AN in SAN, mix morphologies with different crystal growth rates reflects the immiscible nature of the blends. Raman spectroscopy reveals at lower crystallization temperature, for miscible blends, a small amount of SAN is retained in the PCL crystal, with a regular increase in concentration from the midpoint to the edge of the crystal, whereas a homogeneous distribution of SAN is found in immiscible blends. Those distribution of SAN are completely absent at higher crystallization temperatures due to a higher crystallographic order of the PCL crystals.