Thermal study on the impurity effect on thermodynamic stability of the glacial phase in triphenyl phosphite–triphenyl phosphate system

To investigate the impurity effect on thermodynamic stability of the glacial phase, an apparently amorphous metastable phase observed in triphenyl phosphite (TPP), the differential scanning calorimetry (DSC) was carried out in the temperature range 120–350 K for binary mixtures between TPP and triphenyl phosphate (TPPO). Heating up from the glassy liquid, supercooled liquid phase transformed into glacial phase below the crystallization temperature for all the samples with x < 0.2, where x denotes the mole fraction of TPPO. Both transformation temperatures from liquid to glacial and from glacial to crystal increased and temperature range that glacial phase appears narrowed with the content of TPPO. The peak intensity of exothermic effect due to the transformation from liquid to glacial becomes larger whereas that from glacial to crystal reduced. The kinetic and thermodynamic stabilities were discussed for liquid and glacial phases based on the DSC results.