ORIGINAL PAPER

Interaction between microfibrillar cellulose fines and fibers:influence on pulp qualities and paper sheet properties

Jean-Paul Joseleau • Valerie Chevalier-Billosta •

Katia Ruel

Received: 30 November 2011 / Accepted: 14 March 2012 / Published online: 25 March 2012

� Springer Science+Business Media B.V. 2012

Abstract Due to the high potential of cellulose

nanoparticles in composite materials and for both

fundamental and technological considerations, we

investigated the interaction between microfibrillar

cellulose and fibers. The contribution to the paper

properties of fines added to a pulp suspension was

determined. The impact of various proportions of fines

added to a softwood kraft pulp on the paper strength

and how they affected porosity and density was

evaluated. The respective effects of dried fines (dead

fines), originating from paper or board degradation,

and the newly formed secondary fines (fresh fines)

generated during refining were examined. The nature

of the bonding between the fines and the fibers versus

physical retention was characterized in the pulp

suspension. For the first time the respective parts in

the interaction of hydrogen bonds and mechanical

associations were demonstrated and quantified. The

amount of H-bonded fresh fines exceeded that of dead

fines by more than 30 %. The results revealed that, for

both types, the amount of H-bonded fines reached a

threshold, independently of the proportion of fines

added to the fibers. Addition of fines significantly

affected the porosity of papers, fresh fines decreasing

porosity more readily than dead fines. All the results

are convergent to indicate that fresh fines penetrate

more evenly and more deeply into the fiber network

and induce better bonding that produces a closure of

the fiber mat structure. They also demonstrate that

incorporating an optimal proportion of fresh cellulose

fines in fiber networks can bring significant improve-

ment to the final composite material.

Keywords Cellulosic fines � Fine-fiber bonding �Paper sheet density � Porosity �Mechanical properties �Electron microscopy

Introduction

Disintegrated fibers, principally wood pulp fibers,

constitute the main source of microfibrillated cellulose

(MFC) corresponding to individualized microfibrils

with diameters \100 nm that may be considered

nanofibrils (1–100 nm) (Chinga-Carrasco 2011).

During pulping wood fibers are subjected to various

chemical and mechanical treatments. Chemical

pulping of wood removes lignin and some hemicel-

luloses from the lignocellulosic fibers. This results in

improved contacts between cellulose fibril surfaces

due to an increase in lateral cellulose aggregate

dimensions (Hult et al. 2002). Consequently, impor-

tant modifications in the fibers native arrangement as

well as alterations in individual fiber wall cohesion are

observed. The refining step that is generally applied to

J.-P. Joseleau � V. Chevalier-Billosta � K. Ruel (&)

Centre de Recherches sur les Macromolecules

Vegetales (CERMAV), CNRS UPR 5301, BP 53,

38041 Grenoble Cedex 9, France

e-mail: ruel@cermav.cnrs.fr

123

Cellulose (2012) 19:769–777

DOI 10.1007/s10570-012-9693-5

improve fiber bonding capacities and flexibility may

have undesired side effects. In the disintegrated and

dispersed fiber suspension pores of various sizes are

created, inducing negative effects on pulp drainage

and on the final porosity of papers (Kontturi and

Vuorinen 2009). To overcome these effects, chemical

additives, such as starch and derivatives, are added in

the final stage of the paper sheet formation (Lin et al.

2007). On the other hand, another side effect of

refining is to generate small size microfibrillar

elements (Hubbe et al. 2008) originating from the

peeling of the fiber cell wall, generally designated as

secondary fines, which can fill the voids between

fibers, and thus, cause changes in paper properties

(Taipale et al. 2010). Fibrillar fines have been

suggested to induce various kinds of other effects,

sometimes contradictory, such as participating to, or

blocking, fiber–fiber bonding, improving paper

strength properties, decreasing sheet thickness at

equivalent grammage, or influencing porosity (Sirvio

and Nurminen 2004). The void volumes within the

fibrous mat allowing the permeability of air have

significant consequences on paper qualities. In this

respect the role of microfibrillar cellulose fines may be

of great importance, particularly their impact on the

wet end, such as drainage and retention (Pruden 2005;

Hubbe et al. 2007; Liu et al. 2010).

The fine elements generated by disintegration of

wood fibers walls are rather broadly defined. They

consist of elementary cellulose microfibrils (Eriksson

et al. 1998; Ferreira et al. 2000) coated with other cell

wall constituents, such as pectic polymers, hemicel-

luloses and lignin. They correspond to particles c.a.

80 lm in thickness, passing a 200 mesh screen. The

chemical composition of fines may vary according to

the conditions of pulp preparation and the source of

raw material (Luukko et al. 1999; Retulainen et al.

2002; Law et al. 2006; Taipale et al. 2010). Because of

their cellulose-rich nature and high specific surface,

the secondary fines released from fiber surface during

pulp refining (Wistara and Young 1999; Joseleau et al.

2008), contribute to sheet structure and paper strength

(Gorres et al. 1996). Incorporated to pulp fibers they

were shown to influence the drainage rate of the pulp

(Taipale et al. 2010) and paper strength properties

(Backstrom et al. 2008). More generally, MFCs

prepared from mechanical disintegration of fibers

have found important industrial applications such as

reinforcement in biodegradable nanocomposites with

high commercial potential (Nakagaito and Yano 2004;

Hubbe et al. 2008; Siro and Plackett 2010).

The strength of the sheet and the relation between

thickness and density, influencing the sheet gram-

mage, are important aspects of paper qualities. In this

work, for both fundamental and technological consid-

erations, it was of interest to get a better insight about

the interaction between fines and fibers. The conse-

quences of the introduction in a pulp of various

proportions of fines on the paper sheet properties such

as paper sheet strength, porosity and density were

evaluated. The effects of two kinds of fines were

examined, respectively, the dried fines, called dead

fines, originating from paper and board degradation

(Seth 2001), and the newly formed fines, the fresh

fines, generated during fibers refining (Brandstrom

et al. 2005). Although the conditions applied in our

experimentation do not correspond to industrial

practice of pulps (Backstrom et al. 2008), they were

considered appropriate for the fundamental research

that was the objective of this study. The mode of

interaction and the respective part of H-bond and

mechanical retention of the two qualities of fines and

the fibers versus mechanical retention were character-

ized and quantified.

Experimental

Pulp and microfibrillar fines

The pulp used in this work was an industrial softwood

kraft pulp with a kappa number of 30.

The pulp was refined in a Valley beater (according

to standard ISO 5264-2: 2002) at different intensities.

The fines generated during refining were separated

from the bulk of fibers by filtration on a Bauer McNett

apparatus using a 200 mesh filter, then recovered by

decantation. These constituted the ‘‘fresh fines’’ frac-

tion. A part of the fines was subjected to drying for

60 min at 105 �C, until constant weight to insure

complete drying of the MFC material, then re-

suspended in water and disintegrated in a PFI mill at

30,000 revolutions to yield the ‘‘dead fines’’ fraction.

The residual pure fibers fraction was collected and

kept as a suspension in water.

For the evaluation of the capacity of association of

fines to fibers, fines were added in varying proportions

(10–40 %) to the fibers suspension then filtered on a

770 Cellulose (2012) 19:769–777

123

200 mesh filter. In view of getting a general evaluation

of the intrinsic capacity of fines to interact with fibers,

all experiments were carried out in water (Luukko and

Maloney 1999; Zhang et al. 2000) to minimize

electrostatic effects. These are simplified experimental

conditions adapted for the fundamental objective of

this work.

Preparation of paper handsheets

The paper sheets (2.36 g) were made of on a Frank

apparatus equipped with three dryer units, according

to the Rapid-Kothen method (norm ISO 5269-2). The

handsheets containing various proportions of the fines

were conditioned in an atmosphere of 50 % relative

humidity at 23 �C for 24 h.

Evaluation of the fines fraction hydrogen-bonded

in the pulp

Fresh or dead fines (0.25 g) were mixed with a

suspension of fibers (1.0 g) in water (250 ml) for a

proportion of 20 % fines in the pulp. Stirring was

maintained for 20 min and the mixture filtered on a

200 mesh MacNett filter. The fines eliminated in the

filtrate were dried at 105 �C. The pulp retained on the

filter was subjected to the action of a 6 M urea solution

(100 ml) under stirring for 10 min. The mixture was

then filtered and the microfibrillar material passing

through the 200 mesh filter was collected. The

procedure was repeated twice. The pooled filtrates

were freeze-dried and weighed yielding the proportion

of fines that were H-bonded.

Measurement of the physical properties of papers

Mechanical tests for breaking length, tear index, burst

index, and wet zero span were performed in standard

ways according to the norm ISO 5270.

Evaluation of porosity through water absorption

and air permeability

Two methods were applied for porosity measurement.

In the first method the water absorption was measured

in a laboratory apparatus developed at CTP-Grenoble

and consisting in depositing of a calibrated drop of

water on a paper handsheet and evaluating the time

taken for complete absorption of the drop as recorded

by a camera. A drop of water (3.6 ll) was placed on a

paper sample and the time for disappearance of the

meniscus measured. The observation of the evolution

of the meniscus was visualized at 6, 16, 26 and 36 s

with a camera equipped with freeze-frame shot

system.

The second method used for porosity measurement

was by the rate of air flowing through the sheet

under standard conditions, namely the Bekk method

(Chamberlain 2010). In this method (ISO stan-

dard5627/AC1:2002) the flow time of 100 cm3 air is

measured in terms of seconds from a paper sheet

through a flat surface. The measures were performed

on identical samples of fibers added either with fresh

or dead fines. The flow time in seconds of 100 cm3 air

through a paper area of 1 cm2 was measured.

Results and discussion

In a previous study we showed that the addition of

cellulosic fines into pulp fibers significantly influenced

the physical and mechanical properties of the papers.

The effects were considerably different whether

the fines had been dried during the pulp treatments

(the so-called dead fines) or never-dried (the so-called

fresh fines) generated during mechanical refining

(Chevalier-Billosta et al. 2011).

Impact of the addition of fines on sheet porosity

Porosity is a critical parameter for paper quality. It is

defined as the measure of total connecting air voids. In

view of assessing the effects of fines on porosity,

various proportions of fresh or dead fines were added

to pulp fibers, from 0 % to 40 %, and the variations of

porosity due to the incorporation of the fines into the

fiber mesh were measured. Two methods were applied

for porosity evaluation. The first method, in which the

rate of absorption of a drop of water deposited on a

paper handsheet, gives an estimation of the paper

internal cohesion in relation to inter-fiber and fines-

fibers interactions. The looser the interactions, the

more porous the paper, and the fastest the absorption

of the water drop into the paper. The results showed

that for the same proportions of fines added to the

fibers, the water was absorbed much faster when dead

fines were present than when fresh fines were present

(Fig. 1). Interestingly, the phenomenon stabilized

Cellulose (2012) 19:769–777 771

123

beyond 20 % fresh fines incorporated in the fiber net,

indicating a threshold in the capacity of fines to fill up

the voids. This threshold around 20 % is clearly

different from the total capacity of retention of the

fines into the fiber net which goes above 70 % in

weight (see below), suggesting a relationship with the

available specific surface of fibers. Our results are

consistent with the observation that chemical pulp

fines retard dewatering of the pulp suspension due to

their high water holding capacity (Liu et al. 2010) and

to the higher swelling capacity of fresh fines (Laivins

and Scallan 1996).

The second method, known as Bekk method

(Chamberlain 2010), which measures the rate of air

flowing through the sheet under standard conditions,

was performed on identical samples of fibers added

either with fresh or dead fines. For both types of fines

the flow time increased with the amount of fines added

(Fig. 2), although the effect was more pronounced for

fresh fines, in agreement with the reduced porosity

previously observed. This behavior correlates with

Seth’s results (2003), showing that the addition of

fines to the fibers decreased porosity. It is noteworthy

that when fresh fines are present in the paper, the air

volume takes longer to pass through the paper

indicating that the porosity is lowered compared to

dead fines. Thus, both methods demonstrate that the

presence of fines causes a decrease in paper porosity.

For a same percentage of fines added, fresh fines

diminish porosity more readily than dead fines. These

results indicate that cellulosic fine elements have an

important function in the paper formation by influ-

encing inter-fiber bonding. The fresh fines show a

greater aptitude to contribute to the bonding between

fibers than the dead fines. In general, in dried pulps,

dead fines have lost their capacity of interacting tightly

with the fibers, most likely as a consequence of

hornification (Fernandez-Diniz et al. 2004) and self

aggregation (Kato and Cameron 1999).

Impact of the addition of fines on sheet density

Here again, variations of thickness and density of the

papers with the proportions of fines added to the fibers

were not identical whether fresh fines or dead fines

were used. The variation of thickness of the sheet as a

function of the amount of added fresh fines showed an

important decrease up to about 30 % of fines added to

the pulp (Fig. 3) whereas the paper density increased

almost linearly. When dead fines were added, the

variation of thickness of the sheet followed a different

trend, first increasing, at about 10 % fines added, and

then decreasing up to 30 % of fines and then leveled

off. On the other hand the variation of density caused

by the addition of dead fines followed the reverse

evolution, decreasing for 10 % fines added and

increasing slowly with increasing proportions of fines.

Such behaviors induced by the incorporation of fresh

or dead fines, respectively, into the fiber mat shows

Fig. 1 Kinetics of absorption of a drop of water by papers

containing various proportions of fresh or dead microfibrillar

fines. From the compared pictures of the rate of absorption of the

drop of water it is clear that water passes faster through the

papers containing dead fines than those containing fresh fines.

For fresh fines a threshold at about 20 % fines in the paper can be

observed

Fig. 2 Permeability measurement by the Bekk method. The

rate of diffusion of a volume of 100 cm3 through a surface of

1 cm2 of paper, which is inversely proportional to porosity,

shows that the presence of microfibrillar fines in the papers

enhances porosity. Fresh fines have a greater influence on

porosity than dead fines

772 Cellulose (2012) 19:769–777

123

again that fresh and dead fines contribute differentially

to the paper sheet formation and final structure. The

reduction of thickness of the sheet by fresh fines

corresponds to their positive action in tying together

the fibers, bringing them closer, and consequently

increasing the sheet density. This suggests that fresh

fines mediate inter-fiber interactions, exerting a

strengthening effect on the network. On the other

hand, at 10 % of dead fines in the paper, the sheet

thickness is enhanced, suggesting that dead fines do

not favor tight contacts between the fibers. Because

they tend to aggregate, dead fines deposit as clumps

among the fibers (see Chevalier-Billosta et al. 2011)

and thus thicken the sheet.

Nature of bonding involved in fines retention

onto the fiber network

In view of evaluating the yield of retention of the fines

in the pulp and of getting insight about the way they

interact, equal amounts (0.25; 0.50 and 0.75 g) of

fresh and dead fines, respectively, were added to a

given amount of fibers (1.0 g) in suspension in water.

Such ion-free conditions were chosen on the basis of

simplicity and then held constant when evaluating the

behavior and effects of the two types of fines. After

filtration, the retained amount of fines was evaluated.

Figure 4 illustrates with the results of fresh fines

that for the three concentrations, the amount of fine

cellulose elements retained within the fiber network

increased with the amount of fines added. This was

true for both the fresh and dead fines. However, it is

interesting that the total amount retained within the

fibers was always slightly higher with the fresh fines

than the dead ones. Because of the importance of

hydrogen bonds as chemical bonding interaction

between microfibrillar cellulose fines and cellulose

fibers (Joseleau et al. 2008), it was of interest to

evaluate the portion of fines retained on the fibers

through hydrogen bonding. In this objective, we used

the well-known approach developed by biochemists

whereby H-bonds are ruptured in the presence of

strong chaotropic reagents such as 6–8 M urea or

guanidine hydrochloride (Tanford 1968; Higgins

2002; Pace et al. 2005). Thus, after filtration of the

suspension, the fibers were re-suspended into a 6 M

solution of urea. In breaking the hydrogen bonds, the

chaotropic action of urea released that proportion of

fines which was H-bonded to the fibers. The amount of

fresh fines H-bonded to fibers largely exceeded that of

the dead fines, by more than 30 % (Fig. 5). However,

the results revealed that, for both types, the absolute

amount of H-bonded fines reached a threshold and

remained almost constant thereafter independently

of the proportion added to the fibers. Since the amount

of fibers was constant, it can be deduced that the

Fig. 3 Variation of density and thickness of papers according

to the content of fresh and dead fines. The density and thickness

of the paper appear directly related to the amount of fresh fines

whereas a threshold around 10 % is observed when dead fines

are added

Fig. 4 Mode of retention of fines on the fiber net. The amount

of fines retained by hydrogen bonding remains constant

independently of the amount of fines added to the fiber

suspension. Conversely, the amount of fines physically retained

increases regularly. The diagram illustrates the case of fresh

fines

Cellulose (2012) 19:769–777 773

123

observed maximal capacity of fixation by hydrogen

bonding is limited by the specific surface of fibers

which is readily saturated by the fines in the fiber

aqueous suspension. The results also indicate that,

being more individualized, the fresh fines have a

higher specific surface, and thus, more hydroxyl

groups available for H-bond exchanges with fibers

surface than the aggregated dead fines. As a result, the

penetration and distribution of fresh and dead fines

differ in the final paper sheet. Other factors may be

expected to cause differences in the relative tendency

of fresh and dead fines to be retained in the fiber

network, such as stiffness, kinks and zeta potential.

Altogether, fresh fines are more active for strengthen-

ing the network with fibers by opposition to dead fines

which interact more passively with the fibers through

physical entangling. All that may explain that fresh

and dead fines differently influence the paper sheet

properties.

Incidence of fines on the paper sheet formation

and structure

The variations of thickness and density of the paper

sheet show that fresh fines and dead fines are not

incorporated into the fiber network in the same

manner. The inverse relation between thickness and

density is the illustration of the capacity of fines to

favor the contact between fibers and to tighten them

together. This inverse relationship is explained by the

fact that in a paper sheet, the more fines added, the less

fibers per volume unit. As a result, the reinforcing

action of the fines on the inter-fiber bonding

counterbalances the lower proportion of fibers corre-

sponding to the diminution of long elements that have

the capacity to associate. Clearly, the fresh fines show

a better aptitude than the dead fines to contribute to the

sheet integrity and compactness. The foregoing results

showing the differential impacts of fresh and dead

fines are in keeping with the effect of drying on

cellulose microfibrils which has been described as

affecting irreversibly not only the internal organiza-

tion of cellulose chains at the macromolecular level

(Laivins and Scallan 1996; Hubbe et al. 2007) but also

the longitudinal direction of the microfibrils (Kontturi

and Vuorinen 2009). All these factors significantly

impact the paper sheet properties and its quality.

Scheme 1 illustrates a view of how fresh and dead

fines respectively interact with the fibers and are

integrated in the paper mat. The fresh fines have higher

capacity to insert between fibers and keep them

individualized, whereas the dead fines tend to form

aggregates scattered in the void volumes of the fiber

mat, hindering optimal closeness between fibers.

Influence of fines on the paper physical properties

Porosity and density are considered as the most

relevant structural parameters that influence the

mechanical properties of paper (Sirvio and Nurminen

2004). Papers containing fibrillar fines have been

shown to have high tensile strength (Laivins and

Scallan 1996). We studied the influence of fresh fines

on paper physical properties in relation to density of

the sheet and to porosity, respectively. Figure 6 shows

that when fresh fines were added to the pulp suspen-

sion the breaking length increased rapidly to reach a

maximal value for the addition of 20 % fines. On the

other hand, air permeance, as measured by the Bekk’s

method (flow time in seconds of 100 cm3 air through a

paper area of 1 cm2), varied regularly corresponding

to an important decrease in porosity. Zero span,

indicative of intrinsic strength of fibers, decreased

between 10 and 20 % fines added whereas density

showed regular diminution (Fig. 7). The threshold

observed around 20 % fines added for breaking length

and wet zero span was not observed for porosity nor

density indicating that the degree of association of

fines with fibers, determining the mechanical proper-

ties, differs from that determining the compactness of

the paper. This illustrates that the capacity of associ-

ation by H-bonding between fines and fibers is

Fig. 5 Mechanically versus hydrogen-bonded fines. The

proportion of fines interacting with fibers through hydrogen

bonding is higher with fresh fines than dead fines

774 Cellulose (2012) 19:769–777

123

determinant for the tensile properties, and the thresh-

old appears always inferior for dead fines which have a

lower capacity to exchange H-bonds with fibers.

Whereas breaking length and zero span are depending

on the direct interactions between microfibrillar fines

and fibers, and therefore limited by the available

specific surfaces, density and porosity involve the

gross amount of fines that interact with fibers, a part of

which is incorporated in the void volumes of the fiber

meshwork.

Conclusions

Although fresh and dead fines both consist of micro-

fibrillar cellulose elements the results of their action on

Fig. 6 Fresh fines effect on mechanical resistance and porosity.

Fresh fines show a marked effect on breaking length beyond

10 % fines added. In parallel the sheet porosity is gradually

diminished as indicated by the regular increase of the air flow

time measured by the Bekk test

Fig. 7 Fresh fines affect tensile strength and density of paper.

The effect of fresh fines on tensile strength, as measured by the

wet zero span, is observed beyond 10 % fines added. In parallel

the sheet density is gradually increased

Scheme 1 Schematic representation of the interaction of

microfibrillar cellulose fines into the paper sheet fiber network.

Fresh and dead fines added to fibers; t0 = thickness of the sheet

with no addition of fines; t10 = thickness when 10 % of fines

were added; t40 = thickness when 40 of fines were added. At

the highest content the fresh fines tighten the links between

fibers resulting in a higher compactness of the paper. For the

same amount added, dead fines establish less direct chemical

bonds with the fibers and form bulky aggregates that maintain

the fibers apart

Cellulose (2012) 19:769–777 775

123

paper formation and physical properties were not

equivalent. This is important on a practical interest

since the drying occurring during the sheet formation

has negative effects on cellulosic materials. The

microfibrillar fines generated whenever paper materi-

als are recycled have been dried and correspond to

dead fines the ultrastructural characteristics of which

differ from those of the fresh fines newly generated

from pulp fiber erosion during refining. Because of

these differences the two types of fines impacted

differentially the quality of the paper sheet and its

physical properties. In the present work, the ability of

fresh and dead fines to interact by hydrogen bonding

and physical retention, respectively, was quantified for

the first time. This showed the higher potential of fresh

fines to associate to the fiber surfaces by hydrogen

bonding conferring them a higher conformable nature

than the dead fines. Being more individualized than

the dead fines they also penetrate more evenly and

more deeply into the fiber network. Several important

properties of the paper sheet were modified and

improved by the presence of fresh fines, such as tensile

strength, porosity and density. It is worth noting that

the amount of added fines affecting paper mechanical

properties exhibits a threshold of 20 %, whereas

porosity and density are still affected beyond this

limit.

Altogether our results demonstrate that incorporat-

ing an optimal proportion of fresh fines into a pulp can

significantly enhance paper properties and qualities.

We suggest that, if optimal amounts and quality of

microfibrillar cellulose fines present in the pulp

suspension are properly controlled, substantial

improvements of certain qualities of the paper could

be determined, to the benefit of the pulp and paper

industry. By reducing the amount of filler agents the

incorporation of fines should have positive impact on

the environment. The types of the interactions that we

described are inherent to all MFC interacting with a

cellulosic fiber network and may therefore be of

interest for cellulose-based materials reinforced with

MFCs.

Acknowledgments Financial support for this work was

provided by the Association Nationale de la Recherche

Technique (convention CIFRE no 376/2003 allocated to

Valerie Chevalier-Billosta for her PhD thesis). Thanks are

expressed to the Centre Technique du Papier CTP–Grenoble for

technical assistance.

References

Backstrom M, Kolar M-C, Htun M (2008) Characterization of

fines from unbleached kraft pulps and their impact on sheet

properties. Holzforshung 62:546–552

Brandstrom J, Joseleau J-P, Cochaux A, Giraud-Telme N, Ruel

K (2005) Ultrastructure of commercial recycled pulp fibers

for the production of packaging paper. Holzforschung

59:675–680

Chamberlain G (2010) Correlating Bekk air resistance with

Bendtsen air permeability measurements. Appita J 22:

121–125

Chevalier-Billosta V, Joseleau J-P, Cochaux A, Ruel K (2011)

Tying together the ultrastructural modifications of wood

fibre induced by pulping process with the mechanical

properties of paper. Cellulose 14:141–152

Chinga-Carrasco G (2011) Cellulose fibres, nanofibrils and

microfibrils: the morphological sequence of MFC compo-

nents from a plant physiology and fibre technology point of

view. Nanoscale Res Lett 6:417–423

Eriksson LA, Heitmann Jr JA, Venditti RA (1998) Freeness

improvement of recycled fiber using enzymes with refining.

In: Eriksson K-EL, Cavaco-Paulo A (eds) Enzyme appli-

cations in fiber processing. ACS Symp Series 687:41–54

Fernandez-Diniz JMB, Gil MH, Castro JAAM (2004) Hornifi-

cation-its origin and interpretation in wood pulp. Wood Sci

Technol 37:489–494

Ferreira PJ, Martins AA, Figueiredo MM (2000) Primary and

secondary fines from Eucalyptus globulus kraft pulps

characterization and influence. Pap Puu Pap Tin 82:

403–408

Gorres J, Amiri R, Wood JR, Karnis A (1996) Mechanical pulps

fines and sheet structure. J Pulp Pap Sci 22:491–497

Higgins H (2002) Sticking together—how interfibre cohesion

works. The magic of hydrogen bonds. Appita J 55:187

Hubbe MA, Rojas OJ, Lucia LA, Jung TM (2007) Consequences

of the nanoporosity of cellulosic fibers on their streaming

potential and their interactions with cationic polyelectro-

lytes. Cellulose 14:655–671

Hubbe MA, Rojas OJ, Lucia LA, Sain M (2008) Cellulose

nanocomposites: a review. BioResources 3:929–980

Hult E-L, Liitia T, Maunu SL, Hortling B, Iversen T (2002) CP/

MAS 13C-NMR study of cellulose structure on the surface

of refined kraft pulp fibers. Carbohydr Polym 49:231–234

Joseleau J-P, Chevalier-Billosta V, Ruel K (2008) Tracing cel-

lulose elements adsorbed on composite cellulose bioma-

terials by a new labeling method. Biomacromolecules

9:767–777

Kato KL, Cameron RE (1999) A review of the relationship

between thermally-accelerated ageing of paper and horni-

fication. Cellulose 6:23–40

Kontturi E, Vuorinen T (2009) Indirect evidence of supramo-

lecular changes within cellulose microfibrils of chemical

pulp fibers upon drying. Cellulose 16:65–74

Laivins GV, Scallan AM (1996) The influence of drying and

beating on the swelling of fines. J Pulp Pap Sci 22:178–183

Law KN, Song XL, Daneault C (2006) Influence of pulping

conditions on the properties of recycled fibers. Cellul Chem

Technol 40:335–343

776 Cellulose (2012) 19:769–777

123

Lin T, Yin X, Retulainen E, Nazhad MM (2007) Effect of

chemical pulp fines on filler retention and paper properties.

Appita J 60:469–473

Liu H, Yang S, Ni Y (2010) Effect of pulp fines on the dye-fiber

interactions during the color-shading process. Ind Eng

Chem Res 41:8544–8549

Luukko K, Maloney TC (1999) Swelling of mechanical fines.

Cellulose 6:123–135

Luukko K, Laine J, Pere J (1999) Chemical characterization of

different mechanical fines. Appita J 52:126–131

Nakagaito AN, Yano H (2004) The effect of morphological

changes from pulp fiber towards nano-scale fibrillated

cellulose on the mechanical properties of high-strength

plant fiber based composites. Appl Phys A Matter Sci

Process 78:547–552

Pace CN, Grimsley GR, Scholtz JM (2005) Denaturation of

proteins by urea and guanidine hydrochloride. In: Kief-

haber T (ed) Protein folding handbook. Wiley-VCH Verlag

GmbH & CoKGaA, Hamburg, pp 45–69

Pruden B (2005) The effect of fines on paper properties. Pap

Technol 46:19–26

Retulainen E, Luukko K, Fagerholm K, Pere J, Laine J, Pau-

lapuro H (2002) Papermaking quality of fines from

different pulps—the effect of size, shape and chemical

composition. Appita J 55:457–463

Seth RS (2001) The difference between never-dried and dried

chemical pulps. Tappi J 1:1–23

Siro I, Plackett D (2010) Microfibrillated cellulose and new

nanocomposite materials: a review. Cellulose 17:459–494

Sirvio J, Nurminen I (2004) Systematic changes in paper

properties caused by fines. Pulp Pap Can 105:39–42

Taipale T, Osterberg M, Nykanen A, Ruokolainen J, Laine J

(2010) Effect of microfibrillated cellulose and fines on the

drainage of kraft pulp suspension and paper strength.

Cellulose 17:1005–1020

Tanford C (1968) Protein denaturation. Adv Prot Chem 23:

121–282

Wistara N, Young RA (1999) Properties and treatments of pulp

from recycled paper. Part 1. Physical and chemical prop-

erties of pulps. Cellulose 6:291–324

Zhang S, Peterson D, QI D (2000) Effects of fines concentration

on mechanical properties of recycled paper. Tappi recy-

cling symposium, pp 653–661

Cellulose (2012) 19:769–777 777

123