Rheology of cellulose nanofibrils in the presence of surfactants

Abstract

Cellulose nanofibrils (CNFs) present unique opportunities for rheology modification in complex fluids. Here we systematically consider the effect of ionic and non-ionic surfactants on the rheology of dilute CNF suspensions. Neat suspensions are transparent yield-stress fluids which display strong shear thinning and power-law dependence of modulus on concentration, G' ∼ c(2.1). Surfactant addition below a critical mass concentration cc produces an increase in the gel modulus with retention of optical clarity. Larger than critical concentrations induce significant fibril aggregation leading to the loss of suspension stability and optical clarity, and to aggregate sedimentation. The critical concentration was the lowest for a cationic surfactant (DTAB), cc ≈ 0.08%, while suspension stability was retained for non-ionic surfactants (Pluronic F68, TX100) at concentrations up to 8%. The anionic surfactant SDS led to a loss of stability at cc ≈ 1.6% whereas suspension stability was not compromised by anionic SLES up to 8%. Dynamic light scattering data are consistent with a scenario in which gel formation is driven by micelle-nanofibril bridging mediated by associative interactions of ethoxylated surfactant headgroups with the cellulose fibrils. This may explain the strong difference between the properties of SDS and SLES-modified suspensions. These results have implications for the use of CNFs as a rheology modifier in surfactant-containing systems.

Cellulose nanofibril-reinforced composites using aqueous dispersed ethylene-acrylic acid copolymer

“…The lower G 0 of the CNF-EAA suspensions was expected, due to the reduction in CNF concentration by the addition of EAA dispersion and the excess of water. The transition from the linear viscoelastic region to the non-linear region increased with decreasing CNF concentration, the addition of EAA and the excess of water as expected (Quennouz et al 2015). The critical strain value, indicated by the drop in storage modulus, increased from 1.1% for the CNF paste to 2.3% for the CNF-EAA suspension with 0.7 wt% CNF dry content.…”

Steady-shear and viscoelastic properties of cellulose nanofibril–nanoclay dispersions

“…S3), which suggests that wall slip was insignificant. Oscillatory viscoelastic measurements showed that both HCNF and MCNF dispersions were viscoelastic above the gelation threshold (Nechyporchuk et al 2015;Quennouz et al 2016).…”

“…Previous work has shown that aqueous dispersions of slender and kinked CNFs display non-Newtonian rheological behavior characterized by shear thinning and pronounced viscoelastic behavior at concentrations above the gelation threshold (de Kort et al 2016;Jowkarderis and van de Ven 2015;Martoia et al 2016). Recent studies have investigated the effects of pulp source (Tanaka et al 2016), fibril dimension and concentration (Agoda-Tandjawa et al 2010), mechanical treatments (Pääkkö et al 2007), ionic strength (Dong et al 2013), pH (Fall et al 2013), as well as addition of amphiphilic molecules (Quennouz et al 2016) on the rheology of CNF dispersions. Additionally, CNFs can also assist in preparation of homogeneous dispersions of a variety of fillers and pigments, such as carbon nanotubes (Hamedi et al 2014), reduced graphene oxide (Duan et al 2016), TiO 2 (Schütz et al 2012), and CaCO 3 (Lourenço et al 2016) nanoparticles.…”

Nanofibrillated cellulose: properties reinvestigated

“…But, the number of publications in the field is relatively few (Lowys et al 2001;Karppinen et al 2011;Quennouz et al 2016), and the conclusions are often not satisfactorily substantiated due to the inadequate investigation of the modes of interactions of NFC and other system components. The investigations are further complicated by the inadequate knowledge of the proper method of mixing of different components, which has been shown to have a major impact on the recorded rheological properties (Naderi et al 2015b;de Kort et al 2016).…”