| Cellulose is a linear polymer compound composed of glucose units through1,4-β glycosidic bond，having a plurality of active hydroxyl groups. As the earth’s mostabundant renewable resource, cellulose and its derivatives have good chemical stability,biocompatibility, biodegradability, environmental friendiness and have been widelyused in fields of chemical engineering, constructions, pulp and paper-making, etc. Animportant way to explore and utilize cellulose is making it dissolved in a certainsolvent system to obtain a homogeneous polymer solution and then prepare a variety ofcellulose-based material, such as cellulose film, hydrogel, aerogel from it.NaOH/urea/H2O solvent system is a green low-temperature cellulose dissolvedsystem, in which the materials(7wt%NaOH,12wt%urea) are easy to get, pollution-free,inexpensive. What’s more, the dissolve process in NaOH/urea/H2O system is aphysical process and the solvent material is easy to recyle. In addition, the required lowtemperature (-10～-14℃) is easy to achieve both in a laboraty or in a large-scaleindustrial production.This article is based on dissolving cellulose in NaOH/urea systemand prepare a series of cellulose-based material. The main contents are as follows:1. A new non-reactive coagulation system—acetone/water coagulation systemwas adopted to regenerate and prepare cellulose film. The effect of different volumeratio of acetone to water to film-forming ability of cellulose solution was study. Resultsshow that, films regenerated at φ=2.0showed excellent performance both indimensional stability and film-forming ability. Compared to that from pure acetone,cellulose film regenerated from the acetone/water mixture with φ=2.0had morecompact structure, more uniform size distribution and better toughness. The alkaliNaOH, which was capsulated in the film during film formation, could be released atquite a slow rate into the surrounding aqueous solution.2. N,N’-methylenebisacrylamide(MBA) was used to modify cellulose and preparecellulose hydrogel. A series of different degrees of cross-linked cellulose hydrogels canbe obtained by changing the addition amount of MBA. Results show that thetransparency and water absorption properties of hydrogels can be adjusted by thechange of cellulose crystallinity due to the varying amount of MBA. With theincreased addition of MBA, the transparency and the swelling capacity of hydrogelincreased, while the toughness and strength decreased. Hydrogels obtain the best transparency and the greatest degree of swelling when the MBA relative amount is upto90%. Moreover, the hydrogel has a strong adsorption capacity to methylene blue.3. Aerogel can be obtained by freeze-drying. Aerogels with different modifieddegree have been characterized with a lot of methods includes, SEM、TEM、FT-IR、XRD、TGA etc. Results show that structure and properties of aerogel can be changedby altering the amount of MBA. When the relative content of MBA is below60%,cellulose aerogel appears disorder three-dimensional network structure. When MBArelative content reached more than60%, the aerogel transformed into two-dimensionallamellar structure. In addition, a series of aerogels with different structures can beobtained by changing drying conditions in low cellulose concentration. SEM resultsshowed that the aerogel is a fragmental structure when the MBA relative content is60%; when MBA content is90%cellulose aerogels appear a structure of fibrous andfragmented coexistence; it turns into a fibrous structure when the MBA relative amountis up to120%. |
PDF Full Text Request