Glass transitions of poly(bisphenol-A carbonate)/ultraviolet light stabilizer blends by DSC and TOA



Glass transition temperatures are reported for poly(bisphenol-A-carbonate) plasticized by 0–12 wt % of the ultraviolet light stabilizers 2-hydroxy-4-methoxy-benzophenone, 2-hydroxy-4-n-octooxy-benzophenone, and 2-hydroxy-4-dodecyloxy-benzophenone. Differential scanning calorimetry (DSC) and thermooptical analysis (TOA) were employed. The glass transition temperatures increased somewhat with shelf time for the room temperature air-dried 1-mil films drawn from methylene chloride solutions. A Bierbaum scratch hardness of 8.8 kg·mm−2 was observed for a 10-mil poly(bisphenol-A carbonate) film. The effect of load applied to the diamond point (Bierbaum scratch technique) on the shape of TOA transmitted light intensity vs. temperature curves for the resultant scratches was examined. Although the curve shapes are greatly affected, the characteristic TOA temperatures derived therefrom remain essentially unchanged. The glass transition regions are not quite as broad for these polymer/plasticizer blends as they are for compatible polymer/polymer blends. TTOA, the temperature at which birefringence disappears in the scratched films, is found identical to Tf (DSC), the temperature at which the specific heat transition is completed.