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Интеллектуальная Система Тематического Исследования НАукометрических данных |
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Rheology of combined solutions cellulose-PAN, hybrid fibers spinning and their thermolysisтезисы доклада
- Авторы: Berkovich Anna K., Makarov Igor S., Ilyin Sergey O.
- Сборник: Proceeding of Iternational Conference on Rheology and fluid mechanics
- Тезисы
- Первая страница: 45
- DOI: 10.4172/2157-7048.C1.006
- Аннотация: The combined concentrated solutions of cellulose and acrylonitrile copolymers, containing carboxyl groups, in N-methylmorpholine-N-oxide (MMO) were prepared first time using solid-phase activation of powders with subsequent heating to the melting point of MMO. The rheological measurements at 120 and 135°С were performed to estimate the effect of the phase state of the considered combined solutions and the observed morphological transformations on the flow patterns. The addition of PAN to cellulose solutions has practically no effect on solution viscosity at 120°С, but the situation changes drastically during heating of systems to 135°C. This effect can be explained by suppression of the nonlinear elastic reaction of cellulose solutions by PAN macromolecules. With the use of IR spectroscopy, it was previously found that, at temperatures above 130°С in PAN solutions in MMO, the cyclization of nitrile groups with the formation of polyconjugated segments in macromolecules occurs and is accompanied by decrease in viscosity and viscoelasticity. The recorded structural–rheological features of the combined-solution behavior raises a question: Are the observed chemical transformations in PAN macromolecules mainly responsible for changes in the mechanism of the combined-solution flow, or is the flow limited by specific interactions arising between macromolecules of cellulose and the PAN copolymer in an MMO solution? The evolution of the viscoelastic and viscous properties over time was examined in the 25% solution PAN carried out at 120 and 135oC. It was found that the parameters characterizing the viscosity as well as the elasticity of the solution decreased over time. This can be the case only if chemical reactions did not lead to interchain crosslinking but to a change in the chain conformations due to the cyclization discussed above. Degradation of PAN at such temperatures is excluded. Therefore, the rheological data also indicated that the PAN/MMO solutions are “living systems” at elevated temperatures due to partial cyclization of nitrile groups. Thermolysis of the hybrid fibers with a minor PAN content demonstrates a decrease of intensity of the main heat effect at the cellulose carbonization that indicates the strong interaction between PAN and cellulose. In other words, PAN can be considered as the catalyst of the cellulose pirolysis.
- Добавил в систему: Беркович Анна Константиновна