SWELLING AND DISSOLUTION OF CELLULOSE IN NaOH AQUEOUS SOLVENT SYSTEMS

As a fundamental step towards creating a new class of cellulose engineering materials, the proposed research investigated swelling and dissolution of cellulose in NaOH aqueous solvent systems (NaOH/H2O, NaOH/thiourea/H2O and NaOH/thiourea/urea/H2O). The dependence of swelling and dissolution behavior of cellulose fibers on the quality of the solvent was investigated in detail. For the two cellulose samples cotton linter and spruce wood fibers the swelling and dissolution mechanisms in NaOH-water and NaOH-water-additives stayed the same. Adding thiourea to NaOH-water produced the same ballooning mechanism, but with a larger expansion of the balloons, indicating a better solvent. The cotton fiber could not completely dissolve in NaOH/H2O and NaOH/thiourea/H2O. However, the cotton fiber swelled evidently showing no balloon formation and then disintegrated into rod-like fragments in NaOH/thiourea/urea/H2O, which was an indication of the best solvent of all the NaOH aqueous solutions used.