The effect of wall depletion on the rheology of microfibrillated cellulose water suspensions by optical coherence tomography

Saarinen, Timo; Haavisto, Sanna; Sorvari, Anni; Salmela, Juha; Seppälä, Jukka

doi:10.1007/s10570-014-0187-5

Cited by 61 publications

(77 citation statements)

References 39 publications

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“…40,41,63,65,72,73 As mentioned above, these suspensions possess shear thinning behavior, which is observed at wide range of shear rates. In a number of studies, a Newtonian plateau was reported between the low and high shear rate regions 46,64,[74][75][76][77] , and a hysteresis loop was observed when increasing-decreasing (or vice versa) the shear rate 36,65,76 . It is noteworthy that the Newtonian plateau and hysteresis were observed for CNF suspensions produced both without and with chemical pretreatments.…”

Section: Shear Flow Propertiesmentioning

confidence: 99%

“…58,75,77 Owing to such a complex structure, these suspensions exhibited a heterogeneous velocity over the entire height of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 26 the Couette. The height average velocity profiles at different times of steady shear (Figure 9a) also demonstrate the heterogeneous (non-laminar) flow within the Couette gap.…”

Section: Local Flow Propertiesmentioning

confidence: 99%

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Current Progress in Rheology of Cellulose Nanofibril Suspensions

2016

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Cellulose nanofibrils (CNFs) are produced and commonly used in the form of aqueous suspensions or gels. A number of studies have focused lately on rheological properties of CNF suspensions, which gives insight into properties of such materials and can reflect their behavior during handling. This Review summarizes the recent progress in rheological studies on CNF aqueous suspensions using rotational rheometry. Here, we discuss linear viscoelastic properties, i.e., frequency-dependent storage and loss moduli; shear flow behavior, i.e., apparent viscosity and shear stress as a function of shear rate; local flow characteristics, etc. In this Review, we point out that the rheological behavior of at least two types of CNF suspensions should be distinguished: (i) ones produced using mechanical fibrillation with or without enzymatic pretreatment (no surface chemical modification), which possess highly flocculated structure, and (ii) ones produced involving chemical modification pretreatments, e.g., carboxylation, carboxymethylation, quaternization, or sulfonation, which possess better colloidal stability and do not evidently flocculate.

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Section: Shear Flow Propertiesmentioning

confidence: 99%

Section: Local Flow Propertiesmentioning

confidence: 99%

Current Progress in Rheology of Cellulose Nanofibril Suspensions

2016

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“…The gap change data, plotted in Figure , depict the dewatered equilibrium state in respect to sample volume. The final position at which the gap becomes constant is lower for the NFC‐ than MFC‐composite suspensions, related to compaction within matrix . Of interest to the current research here is the gap behaviour during the start‐up of the rotation intervals (CSR), which shows markedly significant gap increase points at the beginning of each rotation cycle, due to the response of the highly viscoelastic structure formed during relaxation in the DSO interval .…”

Section: Resultsmentioning

confidence: 91%

“…Complex systems, as described by the materials used in this study, undergo multiple structural configurations including and generating a variety of elastic interactions . This is reflected using a Physica MCR 300 rheometer with an immobilisation cell (IMC) accessory, as licensed from BASF AG, Figure (a).…”

Section: Methodsmentioning

confidence: 99%

Defining a strain‐induced time constant for oriented low shear‐induced structuring in high consistency MFC/NFC‐filler composite suspensions

Dimić-Mišić

Maloney

Gane

2015

J of Applied Polymer Sci

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Micro and nanofibrillated cellulose is an essentially one-dimensional high aspect-ratio particle material, which can undergo two-dimensional layer (band) structuring under shear. Controlling the evolving rheological properties in aqueous suspension is essential for industrial applications in composite materials. This study focuses on an as yet considered to be unreported phenomenon of structure hardening under low shear. The timescale of the quasi gelation-controlled structure formation under low shear is studied using the large gap vane-in-cup geometry of the Brookfield viscometer. It is proposed that localized structure forms within continuous shear bands, similar to quasi liquid-crystal formation. By extrapolating a characteristic structure growth parameter to the rotation speed at which it becomes zero, the strain-induced structure time constant, t gel , can be obtained as _ c(5 f (X)) 5 1/t gel for the range X 5 10-100/min. The time constant of low shear structure formation is shown to be separable from the static viscoelastic structure build under oscillation in concentrated composite suspension using plate-plate geometry, which is manifest by a Weissenberg normal force response on switching to applied shear, when the time constant of structuration t gel is long.

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“…Seeking for new applications for these materials, the flow properties of CNF-water suspensions are important to understand. Probably owing to the fibres ability to form network structures and flocs, CNF suspensions show strong shear-thinning behaviour even at solids of 1 wt% [6]- [8]. The power-law flow curves is commonly used for mildly attractive colloids [9] including CNF [10].…”

Section: Introductionmentioning

confidence: 99%