THERMODYNAMICS OF THE PHASE-BEHAVIOR OF POLYVINYL-CHLORIDE) ALIPHATIC POLYESTER BLENDS

A series of linear aliphatic polyesters having CH//2/COO ratios in their repeat units from 2 to 14 have been examined for miscibility with poly(vinyl chloride). There is a window of structures in the middle of this spectrum where miscibility is observed. At the low end there is a very sharp boundary lying between CH//2/COO equals 3 and 4 dividing the polyesters which are immiscible with PVC from those which are miscible. At the high end the boundary is not so sharp but rather phase separation caused by a lower critical solution temperature occurs at progressively lower temperatures as CH//2/COO increases beyond 10. Thermodynamic interaction parameters for the miscible blends were obtained by analysis of the depression of the polyester melting point after correction for finite crystal thickness using the Hoffman-Weeks method. A binary interaction model has been used to analyze the heat of mixing data.