A DSC investigation on the stabilizer distribution in PVC blends

The distribution of a liquid organotin stabilizer between the phases of heterogeneous poly(vinyl chloride) (PVC) blends has been studied by differential scanning calorimetry (DSC). This method can be used even at low stabilizer concentrations. At concentrations > 1 wt.-% the stabilizer can be detected in both phases of a PVC/SAN (poly(vinyl chloride)/poly(styrene-co-acrylonitrile)) blend. At lower concentrations no stabilizer could be found in the SAN phase. Determination of the induction period of thermal degradation at 180°C under nitrogen atmosphere showed no loss of thermal stability for blends containing the stabilizer partly in the SAN phase. Kinetic measurements with the DSC indicate a migration of the stabilizer out of the SAN phase, PVC/PMA (poly(vinyl chloride)/poly(methyl acrylate)) blends showed no solubility of the stabilizer in the soft PMA phase.