Rheological Properties of Lignocellulosic Nanomaterial Aqueous Suspensions as Influenced by Water-Soluble Biopolymer Additives

Abstract

Rheological properties including gel strength, steady-state viscosity, and oscillatory rheology of four types of cellulose nanomaterials (CNMs) under the influence of two different biopolymers were studied. The processed CNMs had distinct fiber morphology (individual fibril vs bundles with/without lignin particles), composition (lignin content varying from 52.88% to 6.86%), and surface chemical properties (zeta potential values from −28.62 mV to −13.4 mV). The presence of lignin in lignin-containing nanofibrillated cellulose (LNFC) decreased a suspension’s gel strength, viscosity, and dynamic modulus. The chosen bleached NFC contained large fibril bundles, and the processed material with more individualized fibril and enhanced fluid rheology was demonstrated after regrinding the original NFC. Biopolymer xanthan gum (XG) showed a much larger effect in modifying gel strength, viscosity, and dynamic moduli compared with polyanionic cellulose (PAC). Among the three chosen rheological models, the Nasiri–Ashrafizadeh model fitted the measured shear stress and shear rate data the best for each fluid system with correlation coefficients larger than 0.99. The use of biopolymers (e.g., XG and PAC) helped reduce negative effect of lignin on gel strength and other rheological properties for LNFC. The much-improved rheological performance for biopolymer-modified LNFC suspensions open new opportunities for CNMs to be used as more environmentally friendly fluids for the energy industry.

Lignocellulosic Nanomaterial in an Oil-in-Water Emulsion Fluid System with or without an Emulsifier Sucrose Ester

“…The difference in morphological structure among (L)CNFs was highly influenced by the lignin content. Smaller dimension of fibers for LCNFs could be attributed to the radical scavenging effect of lignin during the mechanical grinding process, which helped hindering interfibrillar hydrogen bonding between fibers. , Nevertheless, there were aggregates in the LCNFs formed by lignin particles. However, the dimensions of aggregates were much smaller compared to the flocs and bundles formed in CNFs.…”

“…Sodium hydroxide treatment did not fully remove hemicellulose in the high-lignin-content system. 25,33 The IR spectra of SE blended (L)CNFs are shown in Figure 1f. Significant increase in the intensity of −OH bands for LCNFs was detected.…”

“…Two types of LCNFs from different sources were used to investigate the effect of the lignin content in LCNFs on stabilizing the emulsions. The lignin contents for both bLCNFs and wLCNFs, measured in triplicate by following modified TAPPI method., − were 52 ± 3.9 and 14 ± 1.2%, respectively. The average acid-insoluble and acid-soluble lignin contents for bLCNFs were 49.8 and 2.2%, respectively.…”

“…A distinctive peak at 1740 cm –1 was observed only in bLCNFs, which could result from unconjugated carbonyl in hemicellulose. Sodium hydroxide treatment did not fully remove hemicellulose in the high-lignin-content system. , The IR spectra of SE blended (L)­CNFs are shown in Figure f. Significant increase in the intensity of –OH bands for LCNFs was detected.…”

“…Lignin content in all three types of (L)­CNFs was assessed using modified TAPPI methods (T222 om-21) with freeze-dried (L)­CNF samples. − Freeze-dried samples of 0.1 g each were placed into each of the four separate 20 mL vials. Subsequently, 1.5 mL of aqueous H 2 SO 4 solution (72%) was added to each vial, and the mixtures were stirred at room temperature for a duration of 2 h. These mixtures were then transferred to 200 mL rounded-bottom flasks with the addition of 56 mL of deionized water.…”