STRUCTURE AND MORPHOLOGY OF CELLULOSE FILMS COAGULATED FROM NOVEL CELLULOSE AQUEOUS SODIUM-HYDROXIDE SOLUTIONS BY USING AQUEOUS SULFURIC-ACID WITH VARIOUS CONCENTRATIONS/

Structure and morphology of the cellulose films coagulated from novel cellulose/9 wt% aqueous (aq.) sodium hydroxide (NaOH) systems (polymer concentration C-p less than or equal to 5.6 wt%) by using aq, sulfuri c acid (H2SO4) with various concentration (C-sa = 20-80 wt%) as coagul ants were investigated. For this purpose two types of alkali-soluble c elluloses with either crystal form of cellulose-I (Cell-I; steam explo ded spruce pulp) or cellulose-II (Cell-II; regenerated from cotton/cup rammonium solution) were utilized. SEM observation on the lyophilized coagulated cellulose films revealed that all the films have basically porous structure more or less, constituted by collision of secondary p articles. Coagulation from two types of cellulose solutions underwent in a quite different way as a function of C-sa of coagulant: (1) For a lkali-soluble Cell-II system, the existence of secondary particles was evident in the range of C-sa greater than or equal to 20 wt% and the most dense structure was given when C-sa = 60-65 wt%, (2) For alkali-s oluble Cell-I system, the secondary particles became detectable at C-s a greater than or equal to 40 wt% and the coagulant with C-sa = 70 wt% gave the most dense structure of the film, and (3) the size of partic les constituting the most dense films is smaller for Cell-II system th an Cell-I system. The coagulant with C-sa greater than or equal to 60 wt% proved to act as strong dehydrant from cellulose solutions by Rama n spectroscopy and the neutralization rate of Cell-II system was much higher than Cell-I system. CP/MAS C-13 NMR analysis showed that both d ensely coagulated films developed practically no intramolecular hydrog en bond at C-3 position.