Miscibility, crystallization and melting behaviour, and morphology of binary blends of polycaprolactone with styrene-co-maleic anhydride copolymers

Blends of polycaprolactone (PCL) and random copolymers of styrene and maleic anhydride (SMA) with different maleic anhydride contents were prepared by the coprecipitation technique. The miscibility of both polymers in the melt and in the solid state was studied by means of optical microscopy, light transmission measurements and dynamic mechanical analysis. The crystallization behaviour of PCL in the miscible blends was examined using optical microscopy and the morphology of the semicrystalline PCL/SMA blends was investigated by means of small-angle X-ray diffraction measurements. Their melting behaviour was studied by differential scanning calorimetry. SMA containing 14 and 25 wt% MA was found to be miscible with PCL over the entire composition and temperature range (up to 200°C). SMA appears to segregate interlamellarly during the isothermal crystallization of PCL. The double melting behaviour of PCL in the blends was attributed to a secondary crystallization process and not to a partial melting-recrystallization-remelting process.