Miscible blends prepared from two crystalline polymers

Abstract

Abstract Differential scanning calorimetry was used to determine the miscibility behavior of several polyester/Saran blends, the two polymers forming these blends being semicrystalline. It was found that Saran is miscible with polycaprolactone (PCL), polyvalerolactone, poly(butylene adipate), and poly(hexamethylene sebacate) since a single glass transition temperature T g was observed at each composition. However, immiscibility was found between Saran and poly(ethylene adipate), poly‐(ethylene succinate), poly(β‐propiolactone), and poly(α‐methyl‐α‐ n ‐propyl‐β‐propiolactone) since two T g 's were recorded at several compositions. Blends were then obtained containing, over a wide range of composition, a miscible amorphous phase and two different types of crystals. From melting‐point depression data on PCL and Saran crystals, thermodynamic interaction parameters χ were calculated and found to be different for PCL‐rich blends and for Saran‐rich blends. This result suggests a variation of χ with composition. Saran is a polymer which does not contain α‐hydrogens and its miscibility with polyesters may result from a β‐hydrogen bonding interaction or a CO/CCl dipole‐dipole interaction.