DSC and p-V-T study of PVC/PMMA blends

Poly(vinyl chloride)/Poly(methyl methacrylate) - PVC/PMMA - blends were investigated by comparative p-V-T and differential scanning calorimetry (DSC) measurements. The study was concentrated on the glass transition range of the blends, and it was found that the blends are characterized by a single glass transition temperature suggesting miscibility of the blend components. It is shown that the glass temperature of the blends increases with both increasing heating rate and pressure. In parallel hereto one observes a decrease in the volume expansion coefficients, which is more accentuated for the polymeric melts than for the polymeric glasses. The dependence of the glass temperature on the composition of the polymer blends shows a sigmoidal behaviour which is due to the fact that positive deviations of the glass temperature from values predicted by additivity rules are observed in the high PVC concentration range, whereas in the high PMMA range negative deviations occur. This suggests a denser packing of the blends and thus a stronger interaction between the blend components in the high PVC concentration range. These packing differences increase with increasing pressure and decreasing heating rate and are generally more accentuated for the glass temperatures evaluated from p-V-T measurements.