Nanofibrillated cellulose rheology: Effects of morphology, ethanol/acetone addition, and high NaCl concentration

Abstract

The effects of ethanol or acetone addition (2.5% to 40% w/w) and high ionic strength (50 mM to 1000 mM NaCl) on the rheology of carboxymethylated (NFC-carb) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized (NFC-TEMPO) nanofibrillated cellulose (NFC) suspensions were studied. Morphological characterization and centrifugation showed that NFC-TEMPO had a much finer overall morphology than NFC-carb. Rheological measurements were taken at 1.3 wt% using a stress-controlled rheometer equipped with cone and plate measurement tools with rough surfaces. The dynamic moduli were investigated through oscillatory stress sweeps. The results showed that as little as 2.5% (w/w) of either ethanol or acetone decreased the viscosity and the dynamic moduli, while 40% (w/w) increased the viscosity to values higher than those of the aqueous suspensions, doubled the storage modulus, and extended the gel-like behavior. Increasing the NaCl concentration from 50 mM to 100 mM drastically increased viscosity; moreover, the storage modulus in the elastic region linearly increased with increasing NaCl concentrations in the range of 100 mM to 1000 mM, suggesting the increased content of interparticle bonds with NaCl addition. The elastic domain was also extended from 10 Pa to 50 Pa and above 500 Pa with acetone addition (40%) and NaCl addition, respectively.

A novel CuFe2O4 ink for the fabrication of low-temperature ceramic fuel cell cathodes through inkjet printing

“…Weaker hydrogen bonding interactions may result in fewer molecular entanglements and less resistance to flow, both of which contribute to lower viscosity. 62 Moreover, the smaller particle size can lead to lower viscosity. 63…”

Populus alba L., an Autochthonous Species of Spain: A Source for Cellulose Nanofibers by Chemical Pretreatment

“…The shear-thinning behavior observed fitted properly the power-law model included in Equation (5): where and are the consistency and flow indices, respectively. Once more, the stiffer samples generated when decreasing pH yielded higher values of the consistency index, whereas the flow index values close to 0 (see inset Figure 6 b) demonstrate poplar CNFs to possess an extremely pronounced shear-thinning behavior [ 69 , 70 ]. Nonetheless, the extreme toughness exhibited by the pH 1 CNF did not allow a proper fit to be obtained as a consequence of the expulsion of the sample during the test.…”

Design and Engineering of Natural Cellulose Fiber-Based Biomaterials with Eucalyptus Essential Oil Retention to Replace Non-Biodegradable Delivery Systems

“…Oscillatory assays were also carried out on the CMC/EO sample (Figure 5b,c). Two different approaches were studied to record the corresponding modulus: (1) for a fixed strain, the oscillation frequency was changed (Figure 5b), and (2) at a fixed frequency (0.01 Hz), the shear stress was changed (Figure 5c) [43]. The results indicated that from the frequency of 0.1 Hz, the storage moduli could not be determined, as verified in Figure 5b.…”

“…In the flow mode, controlled rate flow tests were performed with a shear rate (ẏ) in the range of 0.03 to 1000 s −1 for 180 s to determine the shear stress (т) and viscosity (ƞ). In the oscillation mode, viscoelastic behavior was studied with shear stress in the range of 0.07 to 1000 Pa and a frequency of 0.01 Hz to analyze the storage modulus (G′) and loss modulus (G″) [43]. The frequency value was selected by measuring G′ and G″ parameters at frequencies ranging from 0.01 to 1.0 Hz and applying a chosen stress value, allowing measurements within the linear viscoelastic region.…”