Dissolution and regeneration of cellulose from different sources in an NaOH/urea aqueous system

Cellulose is one of the most abundant natural polymers in the world which has recently attracted the attention of researchers due to it is renewable, biodegradable, biocompatible, nontoxic and hence it serves as a sustainable material for the increasing demand of green products. Ecuador, which has a great biodiversity of plants, has a wide variety of fibrous plants from which cellulose can be extracted for use in different applications, such as films of regenerated cellulose (RC) for industry as well in the field of biomedical engineering. Due to its solvent resistant properties, it is hard to dissolve cellulose. However, within the variety of cellulose solvents; sodium hydroxide (NaOH) is one of the most commonly used due to the fact it is a simple, inexpensive and environmentally friendly solvent. Together with additives, such as urea, it can enhance the solubility of cellulose. This work focused on 1) the dissolution of different natural cellulose fibers as well as industrial type cellulose in NaOH/urea aqueous solution and 2) the fabrication of RC films. It was systematically varied the solvent concentrations, cellulose concentrations and different coagulation media in order to optimize the dissolution process in order to improve the integrity and morphology of the regenerated films. Although it was not possible to fabricate films from all the cellulose samples that were tested, it was found that the best films were obtained from a solvent concentration of 14 wt% NaOH/ 24 wt% urea, cellulose concentration of 5.7 wt% and regeneration from a coagulation bath in 80 v% ethanol.