Phase transitions in pentaerythritol and 2-amino-2-methyl-1,3-propanediol binaries

Abstract

Organic molecular plastic crystals such as polyalcohols and amines reversibly absorb large amounts of heat during solid state phase transitions. These materials have potential applications in thermal energy storage for solar buildings. A binary phase diagram for two such energetic plastic crystals, pentaerythritol (PE) and 2-amino-2-methyl-1. 3- propanediol (AM PL) is proposed. This diagram was determined by high temperature Guinier x-ray diffraction and differential scanning calorimetric methods. The phase diagram in this study is rather complex with two eutectoids at 34°C and 147°C and a peritectic at 184°C. The low temperature phases of PE and AMPL are in equilibrium between 20°C and 84°C in the composition range of 12 to 98 mol % AMPL The solubility of AMPL in PE is very high, up to 45 mol % AMPL in PE at 147°C. The solubility of PE in AMPL is very low. Only up to 10 mol % PE in AMPL at 84°C. The details of detem1inati on of phase equilibria by calorimetry and x-ray diffraction methods are presented.