Thermodynamics, Crystal structure, and Characterization of Bio-based Nylon 54 monomer.
Nylon 54 is a new type of bio-based polyamide and can be applied to many industrial fields. Its raw materials 1,5-pentanediamine and succinic acid are both from biomass and obtained by bio-refinery. High-quality polymer materials require first high-quality monomers. Crystallization was one of the most popular and effective approach to obtain good products. In this report, we investigated the solid-liquid equilibrium of nylon 54 monomer salt in different proportions of methanol-water mixtures at different temperatures and correlated the solubilities with temperature and solvent ratio by the modiﬁed Apelblat model, van't Hoff equation, and (CNIBS)/Redlich–Kister model. It proved it that the solubility of nylon 54 monomer salt increases with the increase of temperature, decreases with the increase of methanol content. Meanwhile, the crystal structural characteristics and thermal behaviors were characterized by the single crystal X-ray diffraction (SCXRD), Powder X-ray diﬀraction (PXRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and hot-stage microscope analysis. The crystallization of nylon 54 monomer salt in different systems was investigated as well, and it was found that the quality of crystal obtained by cooling crystallization in methanol-water system is relatively better in terms of particle size. These studies help us to obtain nylon 54 monomer salt with better quality for polymerization.