PNNL

Abstract

A new calculated phase diagram of pentaerythritol [PE:P C(CH2OH)4]-2-amino-2-methyl-1,3-propanediol [AMPL: (NH2)(CH3)C(CH2OH)2 ] 'plastic crystals' is presented. The low temperature PE-rich * phase has a tetragonal structure whereas the AMPL-rich * phase has a monoclinic structure. Upon heating, these low temperature * or * phases transform to a high temperature * or *' plastic crystal phases. The PE-rich * phase has an FCC structure and the AMPL-rich *' phase has a BCC structure. The system exhibits complex behavior with one low temperature peritectoid, a high temperature eutectoid, and a peritectic. The * and * phases are assumed to be regular solutions and the plastic crystal phases (* and *') are described using sub-regular solution models. The optimization for excess Gibbs energy parameters was perfomred using Thermo-Calc (TCC) software. The magnitudes of the interaction parameters are relatively large compared to those for similar plastic crystal binary systems.