Cellulose (2007) 14:409–417
`DOI 10.1007/s10570-007-9137-9
`
`Viscosity properties of sodium carboxymethylcellulose
`solutions
`
`Xiao Hong Yang Æ Wei Ling Zhu
`
`Received: 2 April 2007 / Accepted: 27 May 2007 / Published online: 29 June 2007
`Ó Springer Science+Business Media B.V. 2007
`
`Abstract Through viscosity measurements, con-
`centration and temperature dependences of viscosity
`of sodium carboxymethylcellulose (CMC) solution
`were recorded. Effects of glycerin, mechanical
`shearing and several electrolytes on the CMC solu-
`tion were also determined. Results showed that the
`viscosity dependence on concentration obeyed the
`Huggins and Kramer equation, the dependence on
`temperature complied with the Arrhenius equation.
`CMC chain could synergize with glycerin, konjac
`glucomannan (KGM), and aluminum sulfate 18-
`hydrate. Sodium chloride, hydrochloric acid, and
`calcium dichloride reduced the viscosity of the CMC
`solution. By suggesting the ion-binding and hydrogen
`bond as the major form of the electrostatic interaction
`in the CMC solution, the synergistic and pseudoplas-
`tic phenomena as well as the maximum over stirring
`time were reasonably explained.
`
`Keywords Electrostatic interaction Ion-binding
`Hydrogen bond Polyelectrolyte Sodium
`carboxymethylcellulose Viscosity
`
`X. H. Yang (&) W. L. Zhu
`
`Department of Chemistry and Environmental
`Engineering, Wuhan Polytechnic University, Hankou,
`Wuhan 430023, P.R. China
`e-mail: yangxh88@yahoo.com.cn
`
`Introduction
`
`Sodium carboxymethylcellulose (CMC) is a deriva-
`tive of cellulose formed by its reaction with alkali and
`chloroacetic acid. Purified CMC is a white to off-
`white, non-toxic, odorless, biodegradable powder,
`which can be dissolved in hot or cold water. CMC is
`used for a variety of applications in a number of
`industries, including the food, personal care, phar-
`maceutical, oilfield and paper industries due to the
`superior properties as a binding,
`thickening, and
`stabilizing agent
`in these end uses. The most
`important character that makes them useful in these
`applications is high viscosity in low concentration.
`Literature has reported some progress in this basic
`concern about both CMC solution and mixture. After
`the apparent viscosity of CMC solutions as a function
`of shear rate,
`temperature, and concentration was
`modeled (Andriana et al. 2002), the steady shear
`viscosity of aqueous CMC solution was measured
`within the power-law range over temperature and
`concentration (Lin and Ko 1995). By studying the
`Newtonian behavior of aqueous CMC solution, effect
`of shear-induced recombination of CMC macromo-
`lecular crystallites was proposed (Jayabalan 1989).
`Recent years,
`rheological behavior of CMC in
`aqueous solution from non-wood pulps was synthe-
`sized and characterized (Barba et al. 2002). Mixtures
`of CMC with natural or synthesized polymers behave
`more complicated viscous properties and attract more
`attentions. In order to evaluate synergistic/non-syn-
`
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`410
`
`Cellulose (2007) 14:409–417
`
`ergistic effects of mixed polysaccharide systems,
`rheological character of the mixture of CMC with
`xanthan was studied under destructive and non-
`destructive shear conditions (Florjancic et al. 2002).
`By means of viscosity measurement,
`the CMC
`interaction with mucin (Rosi et al. 1996) and with
`5-fluorouracil (Nishida et al. 1982), an anticancer
`drug, were reported. Although these works extended
`the knowledge about
`the viscosity of
`the CMC
`solution, aspects of explanation are not sufficient to
`guide the CMC application.
`The sodium CMC molecular structure is based on
`the b-(1?4)-D-glucopyranose polymer of cellulose.
`Different preparations may have different degrees of
`ionizable group substitution, but it is generally in
`the range 0.6–0.95 derivatives per monomer unit.
`When it dissolves in water, an electrolytic process
`takes place to separate a CMC molecule into sodium
`cations and a polymer anion. In this sense, the CMC
`belongs to polyelectrolyte. These ions in solution
`interact with each other through electrostatic forces.
`In addition to this,
`the water molecule and OH
`groups on the CMC molecule exhibit electric dipole
`that performs considerable electrostatic interacting
`force (the so called hydrogen bond). These electro-
`static interactions play a key role to understand the
`viscosity of
`the CMC polyelectrolyte solution.
`Regarding this important issue, investigations have
`been carried out with experiment on the CMC
`solution filled with low molecular weight salt and
`with theoretical model
`for polyelectrolyte. The
`effect of polyion charge on specific viscosity of
`CMC (Trivedi et al. 1987), and viscosity behavior of
`multivalent metal
`ion-containing carboxymethyl
`cellulose solutions (Thomas et al. 2003) were
`studied. Rheological properties of CMC aqueous
`solution with sodium and chromium chloride salts
`were measured (Matsumoto and Mashiko 1988;
`Andreeva et al. 1992). Polyelectrolyte effects in
`the CMC water-cadoxene solution was studied by
`translational diffusion and viscometry methods
`(Okatova et al. 1990). Although several theoretical
`models (Markus et al. 1997; Kunimasa et al. 2004;
`Dobrynin and Rubinstein 2005)
`for
`the reduced
`viscosity of polyelectrolyte solution may be suitable
`to the CMC solution, correlation between electro-
`static interaction and the viscosity properties of
`the CMC solution is not understood well. For
`example,
`the influence of
`ion-binding on the
`
`123
`
`viscosity properties of the CMC solution has seldom
`been reported. Because of the wide applications of
`CMC and its typical representation for polyelectro-
`lyte, investigation into the electrostatic interaction
`by viscosity measurement has practical and theoret-
`ical values.
`In this paper, the viscosities of CMC solutions will
`be measured over concentration and temperature.
`And then, the influences of several added salt ions,
`glycerin, konjac glucomannan (KGM) and shear rate
`will be determined. Recorded curves will be respec-
`tively fitted to Huggins and Kramer equation (Mothe´
`and Rao 1999), Arrhenius equation (Rubinstein and
`Colby 2003), the equation for polyelectrolyte solution
`and Williamson model. Obtained result will be
`discussed with electrostatic and dynamic interactions
`in the solution.
`
`Experimental
`
`Materials
`
`Sodium CMC in this study was made by Shanghai
`Reagent Co., Ltd., of Sinopharm. It was a white to
`off-white, non-toxic, odorless, biodegradable powder,
`which obeyed the Q/CYDZ-03-92 specification.
`Sodium content located in 6.5–8.5%, chloride com-
`pound  3.0%, water  1.0% in weight. The CMC
`were directly dissolved in distilled hot water to obtain
`the solution samples. KGM sample used in our
`experiment was supplied by Hubei Enshi Hongye
`Konjac Development Co., Ltd., which had principal
`properties: granularity  220 mm, glucomannan
`content  95%, protein content <0.6%, ash con-
`tent <3%. The other reagents were chemical grades.
`
`Methods
`
`For the samples, a NDJ-1 viscometer, equipped with
`column geometries of four scales numbered 1–4 and
`working in steady shear mode, was used to measure
`the viscosities. An electromantle water bath was used
`to control the temperature. To measure the shear rate
`dependence, a rheometer AR500 by TA instruments
`was set to steady state flow. A standard steel parallel
`plate with 1,000 mm gap and 40 mm diameter was
`chosen for the steady flow measurement.
`
`

`

`Cellulose (2007) 14:409–417
`
`411
`
`2
`
`The fitting results were evaluated by a standard
`error defined in Eq. (1).
`ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
`r
`P
`ðxmÿxcÞ
`n
`ð1Þ
`range
`where xm was the measured value and xc was the
`calculated value of x for each data point, n was the
`number of data points, and the range was the
`maximum value of xm minus the minimum value.
`Generally speaking, a reasonable fit gives a standard
`error  3%.
`
`Results and discussion
`
`Dissolving process with mechanical stirring was the
`necessary step to make sodium CMC solution,
`therefore it was important to measure the viscosity
`during this process. The measured viscosity data at
`50 rounds/min stirring angular velocity was presented
`in Fig. 1 as hollow diamonds with smoothly lined
`curve for clarity. It showed that viscosity initially
`increased to a maximum, and then decreased to a
`stable value from the moment when CMC was added
`in water to a sufficient long period. Firstly, a part of
`solid CMC dissolving in water resulted in a sharp
`viscosity increase, while the others remained as
`suspended powder, neither swelling nor dissolving.
`With continuous stirring, the majority of the solid
`CMC had dissolved into the water reaching a point of
`
`maximum viscosity without complete disaggregation
`of CMC molecule. Finally,
`the CMC molecules
`reached maximum disaggregation corresponding to
`an unchangeable viscosity value. These phenomena
`in the dissolving process proposed that the CMC
`solution had its maximum viscosity at an intermedi-
`ate state at which the CMC polymer remained some
`molecular binding.
`In order to obtain a basic knowledge into the flow
`properties of the sodium CMC solution, the depen-
`dences of viscosity upon concentration in weight
`percent and temperature were showed in Figs. 2 and 3
`as smoothly lined points of various shape (The
`following figures mean the same). Viewing Fig. 2, it
`was clear that the viscosity exponentially increased
`with concentration. A lot of polymer solution had this
`tendency that was classically described by the
`Huggins and Kramer equation (Mothe´ and Rao 1999),
`
`ln gr
`c ¼ g½ Š þ k2 g½ Š2c
`ð2Þ
`where gr = g/gs was the relative viscosity, g, gs the
`viscosities of the solution and the solvent, g in a
`[g] was a variable traditionally
`square bracket
`denoting the intrinsic viscosity, c the concentration,
`k2 the constant. After curve in the Fig. 2 was fitted to
`Eq. (2), good agreement was obtained. The corre-
`sponding parameters were numerically determined as
`[g] = 115, gs = 31.6 mPa.s, k2 = 0. Standard error
`between the experimental data and the theoretical
`data calculated by Eq. (2) with this set of constants
`was 1.8%.
`
`10000
`
`1000
`
`100
`
`Viscosity (mPa.s)
`
`0
`
`5
`
`15
`10
`Stirring Time (min)
`
`20
`
`25
`
`10
`
`0
`
`1
`
`4
`3
`2
`Concentration (%)
`
`5
`
`6
`
`1500
`1400
`1300
`1200
`1100
`1000
`900
`800
`700
`600
`
`Viscosity (mPa.s)
`
`
`
`Fig. 1 Viscosity variation during the dissolving process of
`CMC in water with a final concentration of 3% by mechanical
`stirring at 50 rounds/min angular velocity
`
`Fig. 2 Viscosity of CMC solution against concentration in
`weight percent
`
`123
`
`

`

`Cellulose (2007) 14:409–417
`
`full of electrostatic interactions, by which ion-binding
`and hydrogen bond might connect
`two or more
`ployions as an effective larger polyion. Just like the
`neutral polymer solution, the temperature stochastic
`process in the solution tended to separate some bound
`ions to an equilibrium state. There was thus a balance
`at which the entire interacting mechanism in the
`solution reached. Each balance corresponded to an
`activation energy value in Eq. (3), which determined
`the temperature dependence of viscosity.
`Beyond these basic properties, sodium CMC
`solution performed much more interesting flow
`properties in the presence of low molecular weight
`electrolytes, which introduced cation and anion into
`the solution, such as NaCl. The properties of the
`CMC solution could be obviously altered by these
`ions. Figure 4 illustrated the influences of various
`ions from added salts on the viscosity of 1% CMC
`solution. It showed that sodium chloride, hydrochlo-
`ric acid, calcium dichloride and ferric chloride
`decreased the viscosity when increasing their molar
`concentration. However, aluminum sulfate 18-hy-
`drate increased the viscosity while increasing its
`molar concentration to reduce the pH value of
`solution from 7 to 6. For aluminum ion, a similar
`result was previously reported for Al3+ to form CMC
`solution as rigid elastic gel (Elliot and Ganz 1974).
`Mechanically, viscosity is the ratio of stress and
`shear rate, which describes the ability for faster fluid
`layer to draw slower fluid layer. The more expanded
`polymer in solution can connect more distant layers,
`so enhances the ability to transfer drawing force from
`
`Al2(SO4)3*18H2O
`NaCl
`HCl
`CaCl2*2H2O
`FeCl3
`
`200
`
`150
`
`100
`
`50
`
`Viscosity (mPa.s)
`
`0
`
`0
`
`0.04
`0.03
`0.02
`0.01
`Molar concentration (mol/L)
`
`0.05
`
`Fig. 4 Effects of various salts on the viscosity of 1% CMC
`solution
`
`1%
`3%
`5%
`
`20
`
`60
`40
`Temperature (°C)
`
`80
`
`100
`
`10000
`
`1000
`
`100
`
`10
`
`1
`
`0
`
`412
`
`Viscosity (mPa.s)
`
`Fig. 3 Viscosities of CMC solutions at 1, 3, 5% concentrations
`versus temperature
`
`the viscosities of CMC
`Figure 3 showed that
`solutions behaved like most water-soluble polymers,
`whose viscosity decreased when temperature in-
`creased. The measured data could be satisfactorily
`fitted to Arrhenius equation given by
`
`ER
`
`gðTÞ ¼ Aexp
`ð3Þ
`T
`where E was the activation energy and R = 8.31 J/
`8K.mole was the gas constant, T was absolute
`temperature, and A was a pre-exponential constant.
`The fitted parameters A and E for 1, 3, 5% CMC
`solutions were 2.29 · 10ÿ4 mPa.s and 3.17 · 104 J/
`mole, 6.50 · 10ÿ4 mPa.s and 3.46 · 104 J/mole,
`3.72 · 10ÿ3 mPa.s and 3.61 · 104 J/mole, respec-
`tively. Standard error between experimental and
`theoretical data for these sets of constants were
`within 2.1%.
`A number of literatures have reported similar
`results for
`the viscosity of neutral hydrocarbon
`polymer solution varying with concentration and
`temperature. They were commonly interpreted with
`both the dynamics of the neutral polymer chains in
`solution and the stochastic effect of the temperature.
`In the case of sodium CMC solution, which belonged
`to a polyelectrolyte solution, electrostatic interaction
`among ions globally existed in the solution. Not only
`the polyions electrolysed from the CMC interacted
`with the small counterions which rendered the system
`electroneutral, but also the electric dipole of the OH
`group on the CMC molecule joined in the interaction.
`As a matter of fact, the CMC solution was a system
`
`123
`
`

`

`Cellulose (2007) 14:409–417
`
`413
`
`Table 1 Fitted parameters to Hess and Klein formula
`c0 (mol/L)
`
`Added salt
`
`g0 (mPa.s)
`
`Standard
`error (%)
`
`NaCl
`
`HCl
`CaCl2 2H2O
`FeCl3
`
`105
`
`112
`
`113
`
`113
`
`0.0958
`
`0.0358
`
`0.0453
`
`0.0309
`
`3.2
`
`3.9
`
`4.2
`
`4.6
`
`here, ca was a constant, and ga was the viscosity
`amount in the absence of added salt. It was clear that
`the variation trend of this equation qualitatively
`agreed with measured data in Fig. 4 for sodium
`chloride, hydrochloric acid, calcium dichloride and
`ferric chloride. Quantitative numerical fitting results
`were listed in Table 1 for these salts. Standard error
`between the experimental data and the theoretical
`data calculated with Eq. (5) were within 5%.
`As an example of the importance of order of
`addition for the small ions, Fig. 5 was a graph of
`viscosity versus salt concentration at 2% CMC
`concentration. In one case, the CMC was dissolved
`in the water before the sodium chloride salt, and the
`salt had a minimal effect on the viscosity of the
`solution. In the other case, the CMC was dissolved
`after the salt, and the resulting final viscosity was
`much lower, especially as the salt concentration
`increased. As pointed out above,
`if the salt was
`dissolved in water before CMC, the salt ion promptly
`shielded the dissolved CMC chains stopping the
`expansion. In contradiction, the salt ion could not
`depress all the expansion by shielding if the salt were
`
`After CMC
`Before CMC
`
`0.01
`
`0.1
`Molar concentration of cation
`
`1
`
`300
`250
`200
`150
`100
`50
`0
`
`Viscosity (mPa.s)
`
`faster to slower fluid layers, and results in higher
`viscosity in the solution. In the presence of low
`molecular weight ions, the ionized –COO groups on
`CMC chain was electrostatically shielded and the
`CMC chains then adapted a less expanded structure.
`The viscosities were thus reduced by the small ions,
`such as sodium cation, chloride anion, hydrogen
`cation, and so on. For gel
`formation, a higher
`concentration was thus required in the presence of
`salts than for a small ion free medium. However,
`when the aluminum sulfate dissolved in the CMC
`solution, hydrolyzing and polymerizing reactions
`occurred in the solution to produce colorless and
`viscous Al(OH)3 colloid. This colloid itself increased
`the viscosity of the CMC solution. Futhermore, the
`OH groups on the colloid had the steric capability of
`binding CMC polyions in solution through hydrogen
`bond. Therefore, the viscosity of CMC solution was
`actually increased by two mechanism. The hydrolyz-
`ing and polymerizing reactions are as follows,
`
`Hydrolyzing reaction 2Al2(SO4)3 + 2n H2O =
`2Al2(OH)n (SO4)3ÿn/2 + nH2SO4
`Polymerizing reaction mAl2(OH)n (SO4)3ÿn/2 =
`[Al2(OH)n (SO4)3ÿn/2]m
`The electrostatic shielding effect commonly exits in
`polyelectrolyte solution. By considering the influence
`of charges on the single hydrodynamics of a poly-
`electrolyte and the cooperative coupling of all parti-
`cles, a formula for viscosity of polyelectrolyte solution
`at low polymer concentration was calculated (Hess and
`Klein 1983). It was expressed as a reduced viscosity,
`cpZ4
`ð2MsMp cs þ ZeffcpÞ3=2
`whereZeff was the effective charge number per polymer,
`Mp andMs the molecular weights of the polymer and low
`molecular weight salt in solution, cp and cs the concen-
`trations of the polymer and salt. When considering the
`dependence of viscosity on the molar concentration of
`added salt, it was beneficial to assume this formula
`could be extended to the solution at high concentration of
`this paper by fixing the other variables at constant.
`On this assumption, a formula describing the effect of
`added salt on the CMC viscosity was proposed as,
`
`gred /
`
`eff
`
`ð4Þ
`
`g ¼ ga
`
`c3=2a
`ðcs þ caÞ3=2
`
`ð5Þ
`
`Fig. 5 The viscosities of CMC solution with sodium chloride
`addition when the salt added after and before CMC
`
`123
`
`

`

`414
`
`Cellulose (2007) 14:409–417
`
`mixture of water and glycerin. At higher than 70%
`concentrations of glycerin, the CMC was not fully
`dissolved in solution and thus did not give as much
`viscosity. There were three OH groups on a glycerin
`molecule. Unlike molecules prefer to interact with
`each other. So it was more reasonable to assume
`hydrogen-bonds on a glycerin molecule bound three
`CMC molecules as an effective larger molecule.
`According to Mark–Houwink equation, this effect
`(the so called synergy) increased the viscosity of the
`solution.
`Other hydrocolloids can also give a synergistic
`viscosity increase with sodium CMC. Figure 8 pre-
`sented an example. If one were to mix a 2% KGM
`solution of 340 mPa.s with a 2% CMC solution of
`380 mPa.s, the net result was not the 360 mPa.s
`average of the two;
`it would be higher than the
`average value. With the ratio of CMC solution to
`total solution rising from 0 to 100%, the viscosity
`went up to a maximum, and then gradually dropped
`down to the average value. As is well known that
`KGM molecule contains glucose and mannose on
`which there are rich hydroxyls. The hydroxyl would
`form hydrogen bonding between the KGM and CMC
`molecules in the solution. There were more average
`electrostatic attractions (hydrogen bonding) between
`unlike molecules, which resulted in this synergistic
`viscosity increase. The occurrence of the interactions
`between KGM and CMC molecular chains through
`hydrogen bond was previously found in blend films
`of KGM and CMC by using FT-infrared, wide-angle
`X-ray diffraction, and differential thermal analysis
`(Xiao et al. 2001). The ratio of synergistic viscosity
`
`dissolved after CMC. The higher ion concentration
`the larger stoppage in the solution leaded to more
`viscosity drops. This effect moderately reduced the
`viscosity when the molar concentration of cation
`increased. Furthermore, a fraction of the CMC chains
`might have bound with each other before the salt
`dissolved. This might be the other reason for the
`viscosity of the solution had much higher viscosity
`value when the salt was added after CMC than before
`CMC.
`Figures 6 and 7 showed examples of the effect of
`water/non-solvent mixtures on the viscosity of CMC
`solution at various concentrations and temperatures.
`In this test,
`the non-solvent was glycerin. With
`increasing glycerin concentration, the viscosity went
`up. The maximum value was reached with a 30/70
`
`5%
`3%
`1%
`
`100000
`
`10000
`
`1000
`
`100
`
`Viscosity (mPa.s)
`
`10
`
`0
`
`20
`
`60
`40
`% water
`
`80
`
`100
`
`Fig. 6 CMC viscosity in water–glycerin solution at 1, 3, 5%
`concentration
`
`Synergistic
`value
`Average value
`
`0
`
`20
`
`60
`40
`% CMC
`
`80
`
`100
`
`700
`
`600
`
`500
`
`400
`
`300
`
`Viscosity (mPa.s)
`
`
`
`20°C
`40°C
`60°C
`60
`40
`% water
`
`80
`
`100
`
`100000
`
`10000
`
`1000
`
`100
`
`10
`
`0
`
`20
`
`Viscosity (mPa.s)
`
`Fig. 7 CMC viscosity in water–glycerin solution at 20, 40,
`60 8C
`
`Fig. 8 Synergistic viscosity with konjac glucomannan
`
`123
`
`

`

`415
`
`20°C
`40°C
`60°C
`
`Cellulose (2007) 14:409–417
`
`10000
`
`1000
`
`100
`
`Viscosity (mPa.s)
`
`to average value could be roughly estimated by using
`Mark–Houwink equation. Considering a simple
`binary interaction, a hydrogen bond connected a
`KGM and a CMC chain as an effective chain that had
`the molecular weight of their sum. Keeping concen-
`trations of CMC and KGM at constant and ignoring
`the small effect of solvent viscosity, the ratio of
`synergistic viscosity to average value could be
`derived as
`
`10
`
`0.1
`
`1
`
`10
`Shear rate (s-1)
`
`100
`
`1000
`
`Fig. 10 Dependence of viscosity of CMC solution upon shear
`rate at 20, 40, 60 8C and 3% concentration
`
`viscosity was higher because random molecular
`orientations exhibited increased resistance to flow.
`In addition to this orientation effect,
`there were
`enough OH groups on a CMC chain, which could
`cause hydrogen bonding among CMC polymers. The
`electrostatically bound state of the CMC chain in the
`solution was not stable. Strong mechanical shearing
`could break some hydrogen bonds in the solution
`leading to smaller effective molecular weight.
`According the Mark–Houwink equation, smaller
`molecule weight corresponded to lower viscosity.
`Due to the relatively high bonding energy,
`it
`suggested that
`this mechanism preferred to cause
`pseudoplastic property in higher shear rate regime.
`The reversible pseudoplastic property of CMC solu-
`tion reflected the break and recover of both hydrogen
`bond and random molecular orientation.
`Due to the behavior of the CMC solution was
`pseudoplastic,
`the most suitable model
`to fit
`the
`experimental curves of viscosity versus shear rate in
`Figs. 9 and 10 might be the Williamson model given
`by
`
`g0
`
`n
`
`g ¼
`1 þ ðk_cÞ
`where k was the consistence index, n was the flow
`behavior index and g0 was the zero-rate viscosity.
`Numerically fitting the data in Figs. 9 and 10 to this
`equation, parameters were determined in Table 2.
`Standard errors between the experimental data and
`the theoretical data calculated with Eq. (7) were
`consistently within 2%. At the same temperature, all
`
`123
`
`a
`
`ratio  ðMCMC þ MKGMÞ
`ð6Þ
`
`
`ðMaCMC þ MaKGMÞ
`Here, MCMC and MKGM respectively denoted the
`molecular weight of the CMC and KGM polymers, a
`the Mark–Houwink constant that usually takes the
`in 0.5*1. No matter what amounts the
`amount
`molecular weights took,
`the numerical value of
`Eq. (6) was bigger than 1 to show a viscosity synergy.
`Figures 9, 10 demonstrated changes of viscosity
`with shear rate at different sodium CMC concentra-
`tions and temperatures. Measured results showed
`totally reversible pseudoplastic (or shear-thinning)
`properties, which meant that the viscosity decreased
`at increasing shear rate. As soon as the shear stopped,
`the viscosity returned to its original value. These
`pseudoplastic properties could be attributed to
`CMC’s long chain molecules that tended to orient
`themselves in the direction of flow. As the shear
`stress was increased,
`the more chains rearranged
`themselves along the shear direction, then the shear
`resistance to flow (viscosity) decreased. When a
`lower stress was imposed on the same solution, the
`
`12
`
`1%
`3%
`5%
`
`100000
`
`10000
`
`1000
`
`100
`
`Viscosity (mPa.s)
`
`
`
`100.1
`
`1
`
`10
`Shear rate (s-1)
`
`100
`
`1000
`
`Fig. 9 Dependence of the viscosity of CMC solution upon
`shear rate at 1, 3, 5% concentration and 20 8C
`
`

`

`416
`
`Cellulose (2007) 14:409–417
`
`Table 2 Fitted parameters to Williamson model
`n
`
`g0 (mPa.s)
`
`K (s)
`
`Condition
`
`Standard
`error (%)
`
`pseudoplastic property of the CMC solution in
`the high shear rate regime.
`
`Investigation into the complicated interaction due
`to Coulomb force in the polyelectrolyte solution is
`one of the most important theoretical problems that
`interest the polymer chemist. CMC not only has the
`properties of both polymer and electrolyte, but also is
`a typical example of the polyelectrolyte. Appending
`the wide variety of application of CMC, the presented
`results in this article have theoretical and practical
`values.
`
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`5% at 20 8C
`3% at 20 8C
`1% at 20 8C
`3% at 40 8C
`3% at 60 8C
`
`1.12 · 104
`1.12 · 103
`1.20 · 102
`5.00 · 102
`1.66 · 102
`
`0.198
`
`0.0879
`
`0.0741
`
`0.0917
`
`0.0129
`
`0.742
`
`0.593
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`0.409
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`0.438
`
`0.410
`
`1.2
`
`1.6
`
`1.5
`
`1.9
`
`1.4
`
`the three parameters increased when concentration
`rose. Among the three parameters the most sensitive
`one was the zero-rate viscosity g0.
`
`Conclusion
`
`the viscosities of sodium CMC
`In this paper,
`solutions over concentration, temperature, and the
`influences of several added salt ions, glycerin, KGM
`and shear rate were determined. Recorded curves
`were respectively fitted to Huggins and Kramer
`equation, Arrhenius equation, the equation for poly-
`electrolyte solution and the Williamson model. By
`suggesting the electrostatic and dynamic interactions
`as well as temperature stochastic process as the
`fundamental mechanism in the CMC solution, the
`measured data were reasonably interpreted. It was
`concluded that:
`
`1. The concentration and temperature dependences
`of viscosity of CMC solution obeyed the Huggins
`and Kramer equation and the Arrhenius equation,
`respectively.
`2. CMC chain could synergize with aluminum ion,
`glycerin and KGM. This character provided a
`useful method to make CMC product of special
`properties, which was required by the increasing
`industrials.
`3. Electrostatic interaction globally existed in the
`CMC solution. It was the key factor to explain
`the viscous properties of CMC solution. Ion
`binding and hydrogen bonding were the most
`important interactive forms.
`4. The balance of hydrogen bonding in CMC
`solution was at quasi-static, which could be
`broken by strong mechanical shearing. This
`mechanism might be one of the reasons of the
`
`123
`
`

`

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`