Phase Transformations in a PAN–N-Methylmorpholine-N-Oxide–Water Systemстатья
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Дата последнего поиска статьи во внешних источниках: 10 апреля 2024 г.
Аннотация:Optical interferometry has been employed to study the mass exchange processes that accompany the dissolution of PAN ternary copolymer and to determine limiting copolymer concentrations in solutions in different crystal hydrate forms of N-methylmorpholine-N-oxide (NMMO). Turbidity spectra, interferometry, and optical microscopy have been used to study the effect of the nature of a precipitant on the phase transformations in the system during solution coagulation and to find the precipitation numbers upon the addition of water and aqueous NMMO solutions (20–50 wt %) to dilute solutions of PAN. In the case of the aqueous coagulant, the precipitation number for a PAN solution in NMMO is almost four times lower than that for traditional PAN solutions in DMSO and DMF due to the high NMMO affinity for water. The analysis of the diffusion processes occurring upon the contact of a PAN solution with coagulants has revealed the conditions for the formation of almost defectless PAN films. These conditions can be used in real casting processes. From this point of view, optimal precipitants for PAN are aqueous solutions containing ~20% NMMO, while 50% solutions do not precipitate PAN.