Phase diagram of binary system PG-TAM

Polyscohols exhibit crystalline transformation which reversibly absorb large amount of heat and can be used for thermal energy storage. The experimental phase diagram of binary system trimethylol ethane-tris(hydroxymethyl) aminomethane (PG-TAM) was established by three kinds of techniques: differential thermal analysis (DTA) method, X-ray diffraction and IR spectra at various temperatures. The phase diagram is characterized by three eutectoid invariants of 71°C, 111°C and 165°C. Infrared spectra of two polyalcohols and their binary system at room temperature show a strong absorption centered at 3347 cm-1 which is identified as the -OH stretching band and indicates that between molecules there are hydrogen bonds which play a dominant role to the structure of the low temperature phase. In the temperature range closely corresponding to the solid-solid phase transition, -OH stretching band shifts to a higher wavenumber, which indicates that the hydrogen bands between molecules are broken. The temperatures of solid-solid phase transition for polyalcohols measured by DTA method are consistent with the results of IR which can declare the mechanism of solid-solid phase transition for polyalcohols. The miscibility of this system was discussed on the basis of intermolecular interactions between ordered low-temperature phase and orientationally disordered high-temperature phase.