Abstract
An attempt was made (1) to prepare porous regenerated cellulose membranes by casting cellulose cuprammonium solutions and then immersing them into aqueous acetone solutions as coagulant, and (2) to investigate membrane characteristics such as radius of secondary particles S2 on the surfaces of the membranes, mean pore diameter measured by the water-flow-rate method 2rf, membrane porosity by apparent density method Pr(d3), and membrane thickness of dry membrane Ld, and (3) to clarify phenomenological effects of solvent-casting conditions on pore characteristics of the membrane formed and to explain the effect in terms of the particle growth theory proposed previously by Kamide-Iijima et al. (KI). Surfaces of membranes prepared by immersing cast solutions in coagulation solution having weight fraction of acetone wAcetone below 0.30 consisted of the secondary particles of polymer-rich phase (referred to as “polymer particle”). As the ammonia concentration in the system was higher, polymer particles of polymer-rich phase grow faster; ammonia was one of the most important factors dominating the size of polymer particles, composing the membranes. Ld was in proportion to the cellulose weight fraction wCell of cast solutions; on the contrary, Pr(d3) and 2rf were inversely proportional to wCell. These experimental findings suggest strongly that density of dried polymer particles increases in proportion to wCell in the solutions. Pore shape in a whole body of a membrane changed drastically from noncircular pores to circular pores when wAcetone in coagulation solutions exceeded 0.30, indicating that wAcetone dominates phase separation conditions such as phase volume ratio R(≡V(1)/V(2); V(1) and V(2) are volumes of polymer-lean and -rich phases, respectively), compositions of phase separation points. Changes in Pr(d3), 2rf and tensile strength TS of the membranes, prepared by using coagulation solutions having different wAcetone, coincide fairly well with that of pore shape. Membranes constructed by larger cellulose particles have larger pores, and this tendency agreed well with results obtained by KI’s lattice theory on pore size distribution proposed before.
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Iijima, H., Iwata, M., Inamoto, M. et al. Phenomenological Effects of Solvent-Casting Conditions on Pore Characteristics of Regenerated Cellulose Membranes. Polym J 29, 147–157 (1997). https://doi.org/10.1295/polymj.29.147
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DOI: https://doi.org/10.1295/polymj.29.147