文摘
The regeneration kinetics of cellulose from cellulose-NaOH-water gels immersed in a nonsolvent bath is studiedin detail. Cellulose concentration, bath type, and temperature were varied, and diffusion coefficients weredetermined. The results were compared with data measured and taken from the literature on the regenerationkinetics of cellulose from cellulose-N-methylmorpholine-N-oxide (NMMO) monohydrate solutions. Differenttheories developed for the transport behavior of solutes in hydrogels or in porous media were tested on the systemsstudied. While the diffusion of NaOH from cellulose-NaOH-water gels into water has to be described with"porous media" approaches, the interpretation of NMMO diffusion is complicated because of the change ofNMMO's state during regeneration (from solid crystalline to liquid) and the high concentration of NMMO in thesample. The activation energies were calculated from diffusion coefficient dependence on temperature for bothsystems and compared with the ones obtained from the rheological measurements. The activation energy ofcellulose-NaOH-water systems does not depend on cellulose concentration or the way of measurement. Thisresult shows that whatever the system is, pure NaOH-water solution, cellulose-NaOH-water solution, orcellulose-NaOH-water gel, it is NaOH hydrate with or without cellulose in solution, which is moving in thesystem. The swelling of cellulose in different nonsolvent liquids such as water or different alcohols duringregeneration was investigated and interpreted using the Hildebrand parameter.
