Rheological Properties of Aqueous Dispersions of Bacterial Cellulose

Abstract

Bacterial cellulose as polysaccharide possessing outstanding chemical purity and a unique structure compared with wood cellulose, attracts great attention as a hydrocolloid system. It was shown, that at intense mechanical action on a neat bacterial cellulose film in presence of water, the gel-like dispersions are obtained. They retain stability in time (at least, up to several months) and temperature (at least, up to 60 °C) without macro-phase separation on aqueous and cellulose phases. The main indicator of the stability is constant viscosity values in time, as well as fulfilling the Arrhenius dependence for temperature dependence of viscosity. Flow curves of diluted dispersions (BC content less than 1.23%) show strong non-Newtonian behavior over the entire range of shear rates. It is similar with dispersions of micro- and nanocrystalline cellulose, but the absolute viscosity value is much higher in the case of BC due to more long fibrils forming more dense entanglements network than in other cases. Measuring the viscosity in increase and decrease shear rate modes indicate an existence of hysteresis loop, i.e., thixotropic behavior with time lag for recovering the structural network. MCC and NCC dispersions even at cellulose content more than 5% do not demonstrate such behavior. According to oscillatory measurements, viscoelastic behavior of dispersions corresponds to gel-like systems with almost total independence of moduli on frequency and essentially higher values of the storage modulus compared with the loss modulus.

Preparation of Cellulose Nanoparticles from Foliage by Bio-Enzyme Methods

“…The concentration of CNF affects the state of its dispersion. As the concentration increases, the CNF dispersion changed from a stable suspension to a gel state [ 15 ]. The CNF prepared in this experiment had a low concentration and presented a relatively stable suspension state, as shown in Figure 2 .…”

“…The FTIR signal scanned at around 3414 cm −1 (3500–3000 cm −1 ) was attributed to O-H stretching vibrations, and the absorption band at around 2918 cm −1 was attributed to C-H stretching vibrations [ 14 ]. The band at 1636 cm −1 was due to -OH groups of the absorbed water [ 15 ]. The peak at around 1382 cm −1 was attributed to C-H asymmetric deformations [ 15 ].…”

“…The band at 1636 cm −1 was due to -OH groups of the absorbed water [ 15 ]. The peak at around 1382 cm −1 was attributed to C-H asymmetric deformations [ 15 ]. The signal scanned at around 877 cm −1 may be due to the asymmetric out-of-plane ring stretching in cellulose (the β-linkage and the amorphous form), which is more apparent in amorphous cellulose and cellulose II [ 16 , 17 ].…”

Исследование Процесса Сублимационной Сушки Бактериальной Наноцеллюлозы

“…При этом происходит удаление большей части влаги от 30,9 % до 50,5 %. Отмеченным [4], создании водных дисперсий с особыми реологическими свойствами [5], использовать в медицине как матрицу-носителя лекарственных препаратов для приема внутрь или в виде покрытия на раны и ожоги [6,7].…”

Viscoelastic properties and flow instabilities of aqueous suspensions of cellulosic fibers: Effects of a gelation agent on dispersion, rheology, and flow stability

“…However, the rheological characterizations of cellulosic suspensions have been generally carried out under stable flow conditions, without the analysis of demixing effects. [ 19‐22 ]…”