Thermodynamic properties of lexan polycarbonate from 110–560°k

The heat capacity of Lexan polycarbonate has been accurately measured on samples of different degrees of crystal Unity. No low temperature transitions are observed in Cp. The usual discontinuity in Cp at the glass temperature is observed at 142°C. for a completely amorphous sample. In semicrystalline samples the change in Cp at Tg is greatly suppressed by the presence of crystallites. The crystalline regions of the polymer exhibit melting over the range 200–250°C. and a latent heat accompanies the melting process. From the magnitude of this latent heat the per cent crystallinity has been calculated as 17% (powder sample) and 24% (solvent crystallized sample). Upon slow cooling from the melt a completely amorphous sample is obtained.