lab sheet 7 lab beating

8/8/2019 Lab Sheet 7 Lab Beating

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CHAPTER I

LABORATORY BEATING OF PULP(PFI MILL METHOD)

7.1 Theory

Beating is refers to the mechanical action of rotating bars opposing a stationary

bedplate on a circulating fiber suspension where the individual fibers are oriented

perpendicular to the bars.

Both mechanical and hydraulic forces are employed to alter the fibercharacteristics. Shear stresses are imposed on the fibers by the rolling, twisting, and

tensional actions occurring between the bars in the grooves and channels of the refiner

or beater. Normal stresses are imposed by the bending, crushing, and pulling/pushing

actions on the fiber clumps caught between the bar-to-bar surfaces.

Refining or beating also produces fines consisting of fragments of broken

fibers and particles removed from the fiber walls. One obvious effect of refining is the

dramatic change in the drainage or dewatering properties of the pulp. Pulp drainability

is rapidly reduced as refining proceeds, mainly due to the increased concentration of

fines.

1

2

3

7.2 Objective

To increase pulp flexibility in determining the ultimate performance of pulp when

converted to paper.

7.3 Machineries and Apparatus

1. PFI Mill Beater

2. Standard Pulp Disintegrator


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7.4 Materials and Chemicals

1. Unbleached Kraft Pulp


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CHAPTER II

EXPERIMENTAL REPORT

7.5 Procedure

7.5.1 Disintegration

1. Transfer the wet pulp nand water used for soaking to the disintegrator.

2. Add distilled water at 205C to give a total volume of 200025cm, theconsistency will then be 1.5%. Set the counter to 0. For pulps with an initialconsistency of 20% or more, disintegrate for 30,000 revolutions. Forconsistencies less than 20%, disintegrate for 10,000 revolutions.

3. Ensure that the pulp is completely disintegrated. Pulp difficult to

disintegrate, such as unbleached sulphate, may require more longerdisintegration than that specified in (2).

7.5.2 Thickening

1. After disintegration, drain the pulp suspension on a Buchner funnel using acoarse filter paper to approximately 20% consistency. To

2. Couch the sheet that has been formed. Mark the sheet on which the drainagetimes are determined (a minimum of three sheets) with an indelible penciland determine their average weight per unit area (gm) separately for

especial accuracy; otherwise it may be taken as that the complete set ofsheets.

7.5.3 Beating

1. Adjust the temperature of PFI mill to 205C before charging and, ifnecessary, that of the pulp such that the mean temperature does not exceed205C during beating.


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2. Make sure the vernier adjusting screw is completely backed of so that nofixed minimum clearance is set between the roll and housing. Under thiscondition the pulp layer will support the full beating load throughout the

beating process.

3. Ensure that the beater is clean. Transfer the 10% pulp suspension to thebeater housing and distribute it as evenly as possible over the wall. See thatno pulp remains on the bottom of the beater housing witin an areacorresponding to the cross section of the roll.

4. Insert the beater roll in the housing and press the cover into position.

5. Set the electronic counter into desired beating revolution. When the counteris set, press the AUTO (START CYCLE) button.

6. After the required number of revolutions of the roll is achieved, the machine

will automatically shut off. Transfer all pulp to a 2000cm graduate. Rinsethe beater with water and add to the cylinder.

7. Dilute the stock with distilled water to 200025cm and clear thedisintegrator for 10,000 revolutions.

8. The pulp is now ready for freeness determination in accordance with T 227,and making and testing of handsheets in accordance with T 205 and T 220.

7.5.3 Calculation

1. The standard drainage time in seconds, d, for the standard condition of 20Cand 60 gm (dry basis), may be found by the formula:

Where,

d = Average drainage time obtained in secondst = Average temperature (C) of the mixture in the cylinderr = Average weight in grams per unit square meter (moisture-free) of the

resulting sheets.Vt = 100 times the viscosity of water in cgs units at temperature, t

dt = d 60-K r-K + 1Vt 1 d-4


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1. In this empirical formula, K is a constant for a given type of pulp, usuallyabout 25, the exact figure for which is preferably determined by experiment by

plotting the observed drainage time ds, against a series of values of r over arange of 50 to 70 gm at 20C, and taking the value of K from the point wherean extrapolated straight line from the plotted points cuts the r axis.

2. To facilitate calculation, Table I gives the values of [(1/ Vt) 1] for differenttemperatures.

Table 1

Temperature(C)

[(1/ Vt) 1] Temperature(C)

[(1/ Vt) 1]

567

891011121314151617181920

-0.34-0.32-0.30

-0.28-0.25-0.23-0.21-0.19-0.16-0.14-0.12-0.10-0.07-0.05-0.020.00

212223

242526272829303132333435

0.020.050.07

0.100.120.150.180.200.230.250.280.310.330.360.39


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CHAPTER III

RESULT AND DISCUSSION

3.1 Experimental Result1) Freeness of Pulp

2) Standard Drainage Time of Pulp

Test Reading(s) Reading 1 Reading 2 Reading 3 Reading 4 Average

1. Consistency (%)2. Temperature (C) 22C 22C 22C 22C3. Drainage Time (Sec) 6.2 6.6 6.5 7.14. Sample Weight (g) (M) 1.10 1.13 1.14 1.145. Sample Area, cm (A) 198.56 201 201 198.566. Sample Grammage,

(gm)

G = 10000 MA

55.4 56.22 56.72 57.41

7. Standard Drainage Timeof pulp, dt

7.25 7.53 7.3 7.825 7.48

Test Reading(s) R1 R2 R3 R4 Avg

1. 1000 ml pulp stock temp. before discharge (C) 22 22 22 222. Temperature (C) 200 210 200 2003. Drainage Time (Sec) 37 37 37 374. Sample Weight (g) (M) 10 11 10 105. Sample Area, cm (A) 227 236 227 227 229.5


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3) Laboratory Results

Figure : The relationship between freeness reading and beating time of unbleachedKraft Pulp

Figure : The relationship between Standard Drainage Time and Beating Time ofUnbleached Kraft Pulp.

Calculation For Standard Drainage Time Of Pulp

d, average drainage time obtained in secondst, average temperature (C) of the mixture in the cylinderr, average weight in grams per unit square meter (moisture-free) of the

resulting sheets.K, constant value for a given type of pulp Approx. 25Formula:

Beating Revolution Freeness Reading Standard Drainage Time1.

5000

i) 532.5 i) 4.71ii) 473 ii) 4.52

Average 502.75 4.62

2.

15000

i) 339.5 i) 6.33i) 298 ii) 6.59

Average 318.75 6.46

3.

25000

i) 217 i) 11.58i) 229.5 ii) 7.48

Average 223.25 9.53


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Standard drainage time of pulp, d = d 60-Kr-K +1Vt- 1 d-4

Diameter=15.9

Area= r2 = 7.95 =198.56 cm

Sample grammage, r

r=10000 mA

r=10000 1.10198.56 cm

r=10000 0.00554

r=55.4 gm

Standard Drainage Time of Pulp

Drainage time, d Temperature, t

1Vt- 1

Constant, K Sample Grammage, r

6.20 22C 0.05 25 55.4

Standard drainage time of pulp, dt = d 60-Kr-K +1Vt- 1 d-4

Standard drainage time of pulp, dt = 6.20 60-2555.4-25 +0.05` 5.42-4


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dt = 189.7 28.54 +0.23 1.42

dt = 6.65 +0.327

dt = 6.98

Diameter=16

Area= r2 = 8 =201 cm

Sample grammage, r

r=10000 mA

r=10000 1.13201 cm

r=10000 0.005622

r=56.22 gm


Drainage time, d Temperature, t1Vt- 1


6.6 22C 0.05 25 56.22


Standard drainage time of pulp, dt = 6.6 60-2556.22-25 +0.05 6.6-4

dt = 231 31.22 +0.05 2.6

dt = 7.4 +0.13

dt = 7.53


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Diameter=16

Area= r2 = 8 =201 cm

Sample grammage, r

r=10000 mA

r=10000 1.14201 cm

r=10000 0.005672

r=56.72 gm


Drainage time, d Temperature, t1Vt- 1


6.5 22C 0.05 25 56.72



dt = 227.5 31.72 +0.05 2.5

dt = 7.172 + 0.125

dt = 7.3


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Diameter=15.9

Area= r2 = 7.95 =198.56 cm

Sample grammage, r

r=10000 mA

r=10000 1.14198.56 cm

r=10000 0.005741

r=57.41 gm


Drainage time, d Temperature, t

1Vt- 1


7.1 22C 0.05 25 57.41



dt = 248.5 32.41 +0.05 3.1

dt = 7.67 + 0.155

dt = 7.825

Average

Average of Standard drainage time of pulp, dt = 7.25+7.53+7.3+7.8254


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dt=7.483.2 Discussion

This standard practice describes the processing of pulp by means of the PFI mill to

evaluate pulp quality for papermaking. In principle, the standard practice applies to all types

of pulp; in practice, the method may not give satisfactory results with certain very long

fibered pulps such as cotton. The standard practice is especially suited to processing test

specimens too small for processing in the Valley beater.

A measured amount of pulp at specified concentration is beaten between a roll withbars and a smooth-walled beater housing, both rotating in the same direction but at different

peripheral speeds. Beating action is achieved through the differential rotational action and the

application of a specified load between the beater roll and housing for a specified number of

revolutions.

Laboratory beating of the pulp is a widely accepted method of simulating commercial

refining practices. Physical testing of laboratory-beaten pulps provides significant data that

aid in determining the ultimate performance of pulp when converted to paper.

The strength properties of a sheet of paper depend on its original qualities, strength of

fibers and on the extent of bonding between fibers that make up the sheet. A paper sheet made

from virgin pulp which has not undergone a form of mechanical treatment is characterized by

low strength, bulkiness, surface roughness and not suitable for papermaking (Bhardwaj et al.,

2004). These undesirable characteristics can be changed to a large extent by treating the pulp

mechanically in a highly controlled manner. This mechanical treatment of fibers is termed

beating (Bowyer et al., 2007; Bhardwaj et al., 2004). The beating of fibers consists of

mechanical crushing and abrasion of fiber caused by contact with edge and faces of rapidly

moving metal bars in the presence of polar penetrating liquid, such as water. Both mechanical


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and hydraulic forces are employed to alter the fiber characteristics. The major effects of

beating on fiber include (Clark, 1985):

i) External fibrillation- the outer layer of the fiber bonds are removed, exposing fibrils

of the secondary wall. New external surfaces are created, which can participate in

polyelectrolyte adsorption and inter-fiber bonding.

ii) Internal fibrillation- intra-fiber bonds are broken and the wall structure becomes

more porous, enhancing water absorption, fiber swelling (hydration) and flexibility.

The fiber wall swelling occurs inwards towards the lumen, with a corresponding

decrease in lumen volume, while the other diameter of the fiber remains unchanged.

iii) Fine formation- pieces of fiber wall depth from the fiber, creating secondary fine.

These can consist of exposed cellulose fibrils from the secondary wall, and material

from the primary wall and middle lamella, in case of high yield pulps.

iv) Release of the chemical components wood polymers and pulping chemicals may be

released during the beating and may in themselves create a cationic demand in the

pulp suspension.

All four effects occur simultaneously, but to different extents depending on the control

of the variable in the beating process. The shortening of fibers improves sheet formation

considerably, thus contributing to paper uniformity and smoothness. However, fiber

shortening causes a large reduction in tearing and folding resistance of the resulting paper, a

proportional reduction in the bursting strength, and small reduction in tensile strength. The

action of crushing the fiber against each other, or between metal surfaces organizes the

bundles of cellulose fibrils, near the surface to become free.

The newly exposed surfaces avidly interact with water molecules producing swelling

and an increase in fiber surface. Both shortening and external fibrillation of the fibers produce

free small fragments of cell wall called fines. Fines greatly reduce the drainage of water in

paper formation by filling pores in the sheet, but provide at same time more fiber - fiber

contact area. It is known that internal fibrillation separates bundles of fibrils located in the


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interior of cell wall of fibers without causing generation of fines. Water is then able to reach

the new surfaces producing swelling and separating individual interior fibrils (hydration). As

a result of the internal fibrillation, the fiber becomes plasticized and more deformable,

improving fiber fiber contact area when pressed and dewatered (Clark, 1985).

INTERNAL FIBRILLATION

Also called cell wall delamination, is the splitting apart of the cell

wall layers into their constituent lamellae. The microfibrils making up the

lamellae have greater adhesion in the tangential than in the radial

direction. As beating proceeds, the fiber wall is delaminated into thinner

and thinner coaxial layers. Cleavage also occurs in the tangential

direction, thus creating an "honeycomb" structure with pores of a few nm,

as shown in Figure 1. The "honeycomb" structure possesses effective local

plasticity in the cell wall and conformability of fibers, which is essential for

sheet formation. As the fibers become soft and flexible, the cell wall, on

drying, tends to collapse into the lumen, giving a ribbon-like structure.

The most visible difference between beaten and unbeaten fibres is that beaten fibres

are fibrillated. When fibre is dried it is in a glassy state, thus the cell wall of the fibre can be

soften by water. During beating internal dissolution is increased and fibrils are separated from

each other. It makes fibres more flexible, thus the bonded area increases. During refining the

internal structure of fibres modifies and bonds which limited the swelling of hemicelluloses

are progressively broken. In pulp of the high yield and in mechanical pulp such restricting

factor is lignin. As the result of swelling fibres become straighter that has positive effect on

the wet web strength.


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Figure 1: The development of internal fibrillation by chemical pulping and

beating


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EXTERNAL FIBRILLATION

External fibrillation is accompanied by removing of the primary wall and making the

fibrils in the secondary wall visible. The main result of the external fibrillation is the

appearance of new surfaces which enhance the possibility of bonding in the drying process.

Primary wall is more difficult to remove from dry pulp and also primary wall of kraft pulp is

more resident then primary wall of sulfite pulp. Also at the external fibrillation fines are

created. Fines are small cellulosic materials that are small enough to pass a 200 mesh screen

(with diameter approximately 76 micro-meters) during fractionating of the pulp.

There are two reasons which prove the importance of the destruction and nature of

exposed fibres surfaces. First of all destruction of the fibre outer layers is able to verify

internal and external fibrillation. Another reason is that the chemical nature of exposed

surfaces which are joined with each other during the next stages of dewatering has a

great effect on the strength of the bonds in paper. Prolonged disintegration of the outer layer

and changing of delignified softwood fibres from polygonal to circular occur during beating,

whereas perimeter length does not change.

Beating or refining of pulp is an essential process of paper manufacture and is carried

out to a greater or lesser degree in all paper and board mills. On the other hand, some

variables such as fiber properties, equipment characteristics and process variables affect

refining process and final pulp and paper properties. Hence a lot of research carried out to

understand the relation between these variables.

The members of the Institute of Paper Chemistry (1944), under the leadership of Van

den Akker, presented a theory for procedure of tear. Van den Akker explained that the initial

rise in the tearing strength/ beating time curve is due to that fact that in the initial stages of

beating, the frictional drag work increases by virtue of tighter enmeshment caused by slightly

increased bonding. During this time only a negligible number of fibers fail in tensile rupture.

As the beating continues, more fibers fail in tensile rupture and therefore, fewer fibers are

pulled intact from the mesh. Since the frictional drag force per fiber is much greater than the


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rupture work, this decrease in the number of fibers pulled intact from mesh causes the tear

strength to decrease.

1. Watson& Dadswell (1964) studied the influence of fiber morphology on paper

properties and indicated the prime importance of fiber length and confirmed the

existence of a critical level of bonding. In short fiber pulp, this critical level of

bonding is never attained in unbeaten pulp, and only rarely in beaten pulp, so that the

tear factor increases with beating. The distribution of stress is less widespread than

with long fiber pulp, and the energy required to pulp out the unbroken fibers is

relatively low, thereby giving rise to a low tear value. In long fiber pulp the degree of

bonding before any beating is generally above this critical level, and any increase in

bonding which results in the reduction of the area of stress concentration, thereby

reducing the amount of energy required in rupturing the paper.

2. Koning & Haskell (1979) evaluated the effects of several papermaking factors- wood

species, pulp yield, type of refiner, amount of refining, wet-press pressure and surface

on strength properties of linerboard weight hand sheets and found that wet press

pressure, wood species, degree of refining and yield were most important. The degree

and direction of the change depend on the particular property. For example, for ring

crush, freeness and wet- press pressure were significant factors for burst, four factors

(species, yield, freeness and pressure) and one interaction (species- yield).

3. Maddern & Franch (1989) studied the main papermaking properties of bleached

soda-AQ kenaf bark and core pulp. They found that the bark fibers are long, thin and

stiff giving good tear and light scattering and moderate bonding. They produce a

bulky sheet with good bonding stiffness. Core fibers are short and wide with thin walls

so that they collapse readily, with little beating, producing a dense, very smooth and

stiff well bonded sheet with good optical properties. The woody core is difficult to

pulp and the pulps, partially in regarded to tears, are lower quality. Morever the pulps

have slower drainage characteristics than wood pulps made by the same processes and

beating. It can be used in special circumstances where low beating requirement and

good smoothness are important.


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4. Schroeter (1994) pulped both kenaf bast and core fibers using a soda-AQ process for

linerboard. He found that the use of kenaf core fiber pulp in place of hard wood pulps

improved sheet smoothness. The bast pulp required only minimal refining while the

core pulp required no refining at all. The letter, when utilized as the top sheet in

linerboard, resulted in reduced energy cost due to refining and improved sheet

smoothness, without negatively impacting the sheet strength properties.

5. Pande and Roy (1998) studied the influence of fiber morphology and chemical

composition on the papermaking potential of kenaf fibers and reported that

hemicelluloses are important for internal cohesion of the cell wall, and their removal

weakens the fiber by reducing inter-fiber adhesion. The removal of hemicellulose

results in the replacement of the relatively flexible cellulose hemicellulosecellulose

bonds by more rigid cellulosecellulose bonds, thus inhibiting the stress distribution,

and resulting in lowered strength properties. The beating energy required to develop a

desired tensile strength decreases with increasing hemicellulose in pulp.

6. Seth (2001) studied the physical properties and response to the refining of never-

dried and dried kraft pulps and reported that never dried pulps require less energy to

reach a given freeness. Although never dried pulps produce wetter web than those

from dried pulps, the webs are stronger. At a given refining energy or freeness, never

dried pulps produce better bonded sheets. These differences are ascribed to the higher

swelling and conformability of never-dried fibers.

7. Rushdan (2003) studied the effect of refining on fiber morphology and drainage time

of soda pulp derived from oil palm empty fruit bunches and found that all fiber

dimensions decreased as the degrees of refining increased. Fiber curling index had the

largest decrease, while fiber lumen width had the smallest. Drainage time increased as

the refining degree increased due to increase in fiber shortening and fine production.

8. Parker et al. (2005) studied the effect of network variables on the ring crush strength

of NSSC pulps from three eucalyptus species and reported unrefined pulps due to low

collapsed fibers produced sheets with ring crush strength. Refining with increasing


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refine easily and develop its strength properties. On the contrary, core pulps, with

much less initial freeness could not be refined without causing difficulties in drainage.

13. Jahan et al. (2009) studied the pulpability within jute plant and reported that core

pulp due to shorter fiber and higher hemicellulose content were easier to beat than

bark and whole plant pulps and produced paper with good properties except tear

index. Jahan & Rawshan (2009) compared the refining capacity and papermaking

properties of jute fiber and Nalita (Trema orientalis)pulps and reported that for a

given drainage resistance, Nalita pulp required less refining energy than that of jute

fiber pulp. Both pulps showed liner relationships between drainage resistance and

refining level. The tensile and burst index of both pulps rapidly developed (drainage

resistance SR 10-30) until they levelled off at moderate level of drainage resistance.

Refining is a process whereby the physical structure of the papermaking fiber is

modified by force imposed in a cyclic fashion. Early research on beating recognized that there

were a number of different beating effects. The older refining literature usually classifies

the effects into three categories; cutting or splitting of the fiber; external fibrillation of the

fibre surface; and internal fibrillation of the fibre surface. Internal fibrillation, the loosening of

the internal structure of the fibre, makes fibre swelling possible; this enhances fibre

flexibility. External fibrillation changes the external surface of the fibre; it makes the fibre

look hairy under an optical microscope resulting in increased external surface area.

Today, we recognize that there are numerous different beating effects in addition to

the ones described above, and all of them are at different times important. For example,

Levlin and Juosunaa (1988) recognize that the effect of the dissolution of hemicelluloses and

lignin from the cell wall material as being the chief effect affecting individual fibre strength

properties. A comparative list of primary beating effects appearing in the literature has been

compiled and is presented in Table 1.


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ii) Successive cleavage of externallayers of the cell wall and theirsubsequent breaking away.

iii) Delamination of internal cell walllayers.

iv) Local dislocations of cell wallstructure, dissolution of the chemicalcomponents of the cell wall andsimultaneous formation of colloidalcarbohydrate solution on the surfacesof the affected fibres.

The beating or refining of pulp changes several end product paper properties

simultaneous. As an empirical rule, paper properties such as tensile strength, burst strength,

folding endurance, internal bond strength, and density are increased whereas opacity,

permeability, and absorbance are decreased. The literature contains many practical rules-of-

thumb pertaining to the practice of beating or refining to archive targeted paper products. It

is commonly known that narrow bars at low speed and pulp consistencies create fibre

fibrillation.

While much is known about the effect of refining, relatively little is known about how

it is carried out. Indeed, most postulated mechanisms of refining have been inferred from

observed changes in fibre properties. Clearly, force is imposed on the fibre in a cyclic fashion

but its magnitude and nature. i.e. hydrodynamic (Frazier, 1988) or mechanical (Goncharov,

1971; page, 1989), has yet to be determined. Alaskevinch (1971) states, in an unsubstantiated

manner, that the beating effect result from fibre fatigue.

The result of beating is a mechanical degradation of fibres and changing of fibres

structure. There are two main beating effects:

i) Primary

ii) Secondary.

Primary effects


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Are divided on external fibrillation, internal fibrillation, cutting, formation of fines, structural

changes, dislocations, micro-compressions, fibre curl and release of chemical components.

Secondary effects

Combine all other effects and changes in the pulp properties which occur during beating, such

as: internal splitting, longitudinal compression, successive cleavage of external layers of the

cell wall and delamination of internal cell wall layers.

Figure 2: The effect of beating on chemical pulp fibres.

Many kinds of papermaking treatment affect on the tensile properties of the wet web.

Extent of fibre-fibre interaction and presence of curl and microcompressions in the

fibres are the main checked factors. Fibre-fibre interactions are mainly improved by

increasing of fiber flexibility, fibrillation, collapse and fines content. Improvement of

fibre-fibre interactions increases wet web tensile strength and stretch. Stretch at high

solids is improved in presence of microcompressions whereas stretch at low solids is

improved by fibre curl.


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Fines of pulp can be divided on two types in conformity with their swellability: finesof unrefined pulp (primary fines) and fines of refined pulp (secondary fines). Fines before

refining mainly consist of ray cells, chunky parts of fibre, commonly less swollen elements,

which promote more opacity then bonding. Fines of refined pulp are more fibrillar and

heavily swelled. They originate from the S1 and S2 layers of the cell wall and operate as good

bonding agents. Very important fact is that less refined pulp for the strength development

depends more on pulp fines than well refined pulp fibres.

Fines properties and fibre fraction properties are not the same and significantly differ

from each other. Fines can bind much water and increase swell better than fibre, since particle

size is very small and surface area is large. Pulp type, fines composition and processing

conditions are very important. Fines of mechanical pulp swell less than fines of chemical pulp

because fines of the mechanical pulp include more hydrophobic lignin and extractives. Fines

content in the mechanical pulp have a great effect on the properties and structure on the fibre

network.

The main effect of fibres on network is enhancement in density which is the reason of

increasing of bonds quantity and thereby paper tensile strength properties are improved.

During sheet formation fines fill free space between fibres and volume of bound water

between fibrils of adjacent fibres is extended, thus Campbell forces are increased. Campbell

forces are surface tension forces called by name of the scientist who first described the

mechanism of these forces in the wet web. Fines can also be as a free bonded filler matter and

create new light scattering surfaces and open compositions. This effect operates only for

mechanical pulp fines because they have both flake-like and fibrillar materials. But this effect

is not valid for fines of chemical pulp, since they include mainly fibrillous material. This

material has very high bonding ability and thus lights scattering cannot be increased. Fines

work as bridge between fibres, thereby promoting formation of coherent paper network.

Therefore local stress concentrations which were developed in the network during straining

are decreased and as a result more even stress allocation is created and strength properties are

improved.


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Beating or refining pulp is the most effective means of improving interfiber bondingand thereby increasing both the density and strength of a sheet of paper. But by so doing, the

dimensional stability of the sheet is reduced. Figure 1(handsheets dried without restraint)

demonstrates the pronounced effect refining has on decreasing the dimensional stability of

paper.(6) As the freeness of the pulp decreases because of beating, the dimensional movement

(between 30% relative humidity [RH] and water soak) of the finished handsheet increases.

This adds support to the general rule that those factors that improve the interfiber bonding in a

sheet of paper also, unfortunately, decrease dimensional stability.

Figure : Effect of freeness of southern pine kraft pulp on the dimensional movement.


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(between 30% relative humidity [RH] and water soak) of handsheets dried

without restraint.

With the exception of papers made chiefly from groundwood, such as newspapers,toilet tissues, and the cheaper grades of printing papers used in the so-called "pulp"

magazines, almost all papers are made from fibers which have been given some sort of a

mechanical treatment. This is termed "beating" or "refining," and is carried out in various

types of machines. These are designed to cut or shorten the fibers and to develop their ability

to cohere when formed into a sheet, and thus to produce the strength and even formation

required in most papers.

Beating has been practiced from the earliest period at which paper was made, and in

all probability the name originated from the crude methods employed at that time, or even

when papyrus was used. The method of preparing sheets of papyrus involved pounding the

moistened strips to make them adhere, and later methods of making paper from bark included

wetting it, placing it on stones and pounding it with a club or mallet. The original Chinese

method of preparing fibers for papermaking was to place the bark or cloth in a stone mortar

with a little water and pound it with hand-operated pestles or mallets until the fibers were

sufficiently separated. All of these operations are distinctly "beating," and included little of

the cutting action which is a function of many of the modern beaters and refiners.

In the Chinese method of beating the mortars were frequently set in the ground and the

pestles or hammers were raised by hand, or later by workmen treading on the ends of levers or

tilt-bars. The hammers probably had a weight of 60 to 70 pounds and dropped on the stock

from a height of 8 to 12 inches. This laborious method of beating was somewhat improved

about 1151 when a stamp mill operated by water power was invented in Spain. Mills of this

stamp type consisted of rows of great wooden hammers operating up and down in troughs

known as "vat holes," which were made from stone or from logs of oak, with their cavities

lined with lead or iron. Later, probably toward the seventeenth century, the stampers were

somewhat modified according to the kind of work they had to do. For the first treatment of

rags the hammers were faced with iron spikes or teeth, which aided in fraying out the cloth.

While this treatment was being given, a stream of water was run through the trough to

carry the loosened dirt away through holes in the sides of the containers. Loss of fiber was


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prevented by screens of horsehair over the holes. When the rags were partly broken down and

washed, they were bailed out into another stamper where the beating and washing was

continued with more lightly shod stampers. The final treatment was in a third set of stampers,

which were usually not metal faced, and which operated without the stream of water, because,

at this stage of the beating, water would have removed too much fiber.

The number of such stamp mills in a plant naturally varied with the amount of paper

being made, and as there is little information regarding the output of any of the early mills the

capacity of a stamp mill can only be guessed. A good German mill early in the seventeenth

century was said to have as many as twenty-five troughs, each with five stampers. Such stamp

mills as these were used in the early American paper mills, notably the Willcox mill

previously mentioned. It is not known when they went out of use, but it was probably not far

from 1780 in America and somewhat later in Europe.

It is obvious that this manner of beating must have caused little shortening of the

fibers, and that its chief function was to fray out their ends and split them lengthwise into

long, slender fibrils. It is claimed that beating of this sort, together with the absence of alum

and other chemicals in the paper, was responsible for the high strength and durability of

papers of this period. This may be true, but the opinion is necessarily based on papers which

have survived, and cannot be influenced by those papers which were so poor as to have

perished. That there were such papers is proved by a statement of the Dutch archives in 1670

saying that papers (presumably of Dutch origin) cracked when folded, and after a few days

could be rubbed to fragments between the hands. It seems that such a state of affairs must

have been caused by the preliminary treatment of the rags, rather than by the beating

operation itself.

It is generally considered that the essential features of modern beaters were first

employed about 1680, when some Dutchman whose identity is unknown developed a beater

consisting of a tub with rounded ends in which revolved a solid wooden roll, on the surface of

which were fixed about thirty iron knives. This roll revolved directly over a bedplate made of

stone or metal, which was fixed in the bottom of the tub. As the roll turned, the fibrous

material was dragged between the bedplate and the knives and lifted over a backfall, down


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which it slid to complete its course around the tub. Beaters of this type are in common use

today and are known as Hollanders because of the country of their origin.

Whether the date of 1680 is correct seems to be questioned by A. Blum in his book

"On the Origin of Paper." In this he states that the Fabriano mill in Italy produced in 1268

1276 a rag paper from flax or hemp in which the pulp was ground more thoroughly by metal

beaters than stock produced by stamp mills. In this paper the fibers were short and it was

sized with gelatin and water-marked. This distinguished it from paper made in the Arabic

manner, which was of long fibers beaten with pestles, and sized with starch. This question is

merely of academic interest, but a bit of evidence tending to support Blum was supplied by a

European paper made in 1486 in which the linen fibers were much shorter than most rag

stocks treated in modern beaters, and many showed ends cut or broken sharply across.

Beaters of the Hollander type were in use in Germany as early as 1710, and in 1725

one such beater was said to prepare as much stock in a day as eight stamper mills could make

in eight days. The change from stampers to Hollanders was gradual, and for some time both

types were used in many mills, the stampers for breaking down the rags and the Hollanders

for finishing the beating. Hollanders were used in America at least as early as 1775. All but

one of the English mills had discarded stampers by 1810, but until 1861 the French

government insisted that all paper for the stamp office be made from fibers beaten in stamp

mills.

The principle on which the Hollander operates is still that of many modern beaters and

the chief changes have been made to improve the efficiency and control of the beating and the

capacity of the beater tubs. Literature of about 1885 mentions rag washers as having

capacities of about 150 pounds of rags, and as late as 1888 trade journals mentioned the

installation of new beaters of 600 pounds capacity. Today a beater of 1,000 pounds is

relatively small and some will hold from 3,000 to 4,000 pounds.

There are many different kinds of beaters of this general type, varying in size and

shape of tub, weight of roll, number, thickness and spacing of roll knives, and position and

type of knife filling the bedplate. These changes were all designed to increase the speed of

beating and improve the quality of the beaten fiber in some way, but none has proved so

outstanding that it has replaced all the others. Like much of the other machinery in a paper


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mill the cost of replacement is so high that once a beater is installed it is used more or less

regardless of its efficiency. This is largely due to the fact that the efficiency of a beater may

be calculated mathematically according to a number of theories, but can be proved only by

practical operation. It is, therefore, necessary to install and use a beater in order to be certain

that it is satisfactory.

In using a Hollander the sequence of operations includes filling, or "furnishing,"

beating and dumping. Furnishing includes adding water and fibers until the desired quantities

are present. The fiber may be in slush form, or in lap form containing 30 to 50 per cent of

fiber; or in dry sheets or roll fiber, each of which is usually about 90 per cent dry fiber.

Sometimes wet waste, or "broke," from the paper machine is added, or dry broke or waste

from the sorting room which has been put through some form of kneader to reduce it to a

semi-pulped condition. As will be discussed later, fillers, coloring matters and sizing agents

are customarily added to the pulp in the beater.

After the furnishing has been completed the beating is begun by lowering the roll

toward the bedplate. This is done by turning a wheel which operates through a worm and gear

to move one end of a lever on which the bearing of the roll shaft rests. A shaft attached to the

hand wheel extends across the beater tub to a similar device on the other side, so that both

ends of the roll are raised or lowered an equal amount. Adjustment in this way is very

sensitive, and requires great skill and judgment for the best work. The setting of the roll may

be judged by placing one end of a rod against the end of the bedplate and the other end of the

rod in the ear; then the vibrations will tell the experienced man how hard his roll is set.

Sometimes the degree of beating is specified as so many turns of the hand wheel,

starting from the position when the roll just touches the bedplate. This requires almost as keen

judgment in determining the starting point as in beating entirely by sound. There are also

mechanical devices which weigh and record the pressure exerted by the roll on the stock, or

which show the linear distance of the roll from the bedplate, but much the most common

method of operating is still that of setting the roll by hand.

The amount of beating, as well as its severity, depends on the kind of paper being

made and the fiber used. For example, papers as different as blotting and hard rattly bond can


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be made from the same rag stock by proper regulation of the beating. When rag stock was the

fiber in common use the beaterman judged the degree of beating by taking a little of the

beater contents in his hand and squeezing it. This same method was also employed in judging

the length of the fiber delivered by the jordans, and experienced men became remarkably

proficient in regulating their beating in this way. Since the use of chemical woodpulp has

become so general the necessary shortening of the fibers is much less, and the art of beating

by hand-testing has almost completely disappeared. It was probably never as skilfully carried

out as the beatermen thought, for recording devices have proved that hand setting of the roll

could not be done the same by different individuals, and not even twice alike by the same

person.

When the beating in the Hollander is considered finished its contents are dumped

through a large valve in the bottom of the tub into a tank or chest fitted with an agitator, and

often known as the jordan chest because the stock next passes to the jordan. Dumping a beater

requires care and system. Some water is necessary to enable the stock to flow out readily, but

the amount used should not vary too much because the consistency of the stock going to the

jordans should be practically constant in order to enable it to do uniform work. From the

jordan chest the stock passes through the jordan to another chest which supplies the paper

machine, and hence is called the machine chest. The placing of a second jordan (or other

refiner) between the machine chest and a paper machine makes it possible to change the

character of a paper more quickly than is possible if stock is accumulated in the machine chest

before the effect of beating can be tested on the paper machine.

Beaters of the Hollander type require much floor space and their power consumption

is highmuch the greater part of the power being used to circulate the stock, rather than in

useful beating. Some beaters can handle stock at 8 per cent concentration, but most are

operated at 5 to 6 per cent. The control of the beating action is not too good and the action of

the roll can change with the wearing away of the knives of the roll and of the bedplate. These

shortcomings, and the desire for continuous, rather than batch operations, led to the

development of the Kingsland refiner in 1856, the jordan in 1858, and since then a

considerable number of others, which work on similar principles, but with different

mechanical devices. Most of these devices consist in principle of two discs, one or both of

which revolve, and between which the fibers pass from the center of the discs to the


31/39

periphery. The inner faces of the discs are lined with bars or grinding surfaces of various

kinds according to the character of the stock and the purpose for which it is to be used. The

distance between the discs influences the capacity of the refiner, as well as the degree of

beating of the stock, and it can be controlled accurately by proper mechanical devices.

The jordan, which has been widely used for a long time, consists of a conical plug,

covered with longitudinal knives, which fits into a conical shell similarly lined with knives. A

means of moving the plug in or out with respect to the shell enables the distance between the

knives of the plug and those of the shell to be accurately adjusted so that the treatment of the

stock can be varied from a light brushing action to one of sharp cutting. This permits

considerable variation in the quality of paper made. The stock enters at an opening in the

small end of the shell, passes spirally around the rapidly revolving plug, and is discharged at

the large end by the centrifugal action of the plug. Originally the jordan supplemented the

beater and was supposed to give the finishing touches to the stock and to even out inequalities

in the stock from different beaters. Its function was much more important when beating long

fibers, such as cotton, linen and hemp, than it is on chemical woodpulps. Today some mills

have completely eliminated beaters and depend entirely on jordans or other refiners for their

stock preparation (fiber treatment). This is true of such widely different papers as kraft

wrappings and glassine paper. Other mills, notably those making newsprint, have done away

with beating entirely and meter both the groundwood and sulfite directly to the paper

machine.

Jordans and refiners require that the stock be supplied to them in slush form and

preferably at a constant fiber concentration. The jordan can handle stock of 2 to 4 per cent

concentration, but 3 to 3.5 per cent is the usual practice. Hollanders and other beaters of

similar construction can be partially filled with water and then dry sheet or roll fiber can be

fed in until the desired concentration is reached, though this is not considered to be the best

practice.

In spite of all the developments which have been made in beaters and refiners, and all

the study which has been given to the subject, there is still no sound, basic knowledge which

will enable a mill to select the best equipment for any given type of paper. Probably there is

no "best beater," at least so far as its effect on the paper is concerned, and an equally good


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sheet can be made from stock prepared in any good beater if it is properly handled. There is

still much argument as to whether tub beaters are necessary and whether all the work cannot

be done better in jordans or other refiners. This unfortunate and confusing state of knowledge

is due to the impossibility of assembling and comparing large scale units of the different

beaters which can then be used in preparing different fibers for a variety of types of paper.

The changes which take place in fibers during beating profoundly affect the character

of the paper which can be made from them. Some of the changes can be seen when the fibers

are examined under a microscope, but in many instances there is a marked change in the

papermaking properties with no commensurate visible change. In general it may be said that

the outer surface of a fiber consists of a network of fibrils, while the inner, secondary wall has

parallel bundles of fibrils of the same general dimensions. Beating tends to remove that

portion of the outer surface which remains after the processes of cooking, bleaching and

purification. As beating proceeds further, the inner wall of the fiber starts to swell and

disintegrate. Beating for most grades of paper involves only the first of the process, but for

glassine papers it goes nearly to completion.

Fibers vary greatly among themselves in the way they respond to beating treatments.

Hemp, linen, and to a less extent cotton, tend to split lengthwise into fibrils which are

considerably longer and more slender than those from wood fibers. These fibers, therefore,

are of special value in making such thin and opaque products as the Oxford India papers so

largely used in printing Bibles and Prayer Books. Other fibers, such as sulfite and sulfate from

coniferous woods, split very much less than linen, and hence are not suitable for very thin

papers. The fibers from deciduous woods are naturally short and do not show visible effects

of beating nearly as much as the long fibers, though there is a distinct change in the strength

of the paper as the beating of such fibers proceeds.

Besides the type of fiber there are numerous other factors which may greatly influence

beating. Degradation of the fibers may be caused by too severe treatment in the cooking

process; too much bleaching, or bleaching at the wrong degree of acidity or alkalinity; contact

of the fibers with acid, as in the drainer bleaching of rag stock which was acidified to hasten

the bleaching action; or too high a temperature during bleaching. All of these may so

seriously affect the fiber and its beating that the papers made from it are of very inferior


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quality. On the other hand, it is possible to have a fiber so highly purified that it has no

papermaking value, as proved by a fiber of 99 per cent alpha-cellulose content, which could

not be so beaten as to produce sheets which were strong enough to handle.

Besides these influences which cause variations, there are the different types of beaters

and refiners with their different kinds of bar fillings, different speeds, and possible degrees of

adjustment. Most of these have been designed to perform certain features of beating, such as

cutting, or "hydration," but their action is so obscured by other factors of beating and

papermaking that it is difficult to isolate the action of the beating device itself.

The term "hydration" is only one of those used to describe those properties of pulp

caused by beating. "Freeness," "slowness," "wetness" or "greasiness" are also applied as

descriptive of the rate at which water drains from the stock, or the way it feels when grasped

in the hand and squeezed. Although "hydration" is very generally employed to describe this

effect of beating its selection is particularly unfortunate because it seems to imply an actual

chemical combination of water with the fiber substance. For many years there was active

discussion of this theory, but at present it seems to be generally assumed that the effect is due

to a softening and swelling of the fiber caused by penetration of the water between the fibrils.

Whatever its cause, the effect of pronounced "wetness" or "hydration" in a beaten

stock is to reduce the rate at which it will drain on the paper machine wire and hence reduce

the speed at which the machine can be run, as well as its output of paper. It also causes a

tendency to slide on the cylinder machine molds and to "crush" under the dandy roll of the

fourdrinier machine, both of which cause defective paper. In the paper itself beating induces

greater shrinkage, density, hardness, and translucency. Such effects are noticeable to an

extreme degree in papers of the glassine type.

Almost without exception, paper consists of a heterogeneous mixture of fibers ranging

from long to very short. The proportions of long and short depend on the kind of fiber used

and the degree of beating, which is merely another way of saying the type of paper. This

variation in length is due to the fact that not all of the fibers receive the same amount of

cutting in the beaters and jordans. In fact this could hardly be otherwise considering the

enormous number of fibers in a beater and the chances that many will completely escape


34/39

passing between two knives in such a way as to be cut. Probably the effect of variations in

length is beneficial in most papers because it helps to average out the various strength factors,

and thus make a more generally acceptable sheet.

As the degree of beating increases, the bursting, tensile and folding strengths of the

paper increase. Tearing strength rises rather quickly to a maximum and then drops off with

increased beating. At the same time shrinkage of the sheet on drying increases and also its

susceptibility to change in dimensions with varying humidities in the surrounding

atmosphere. In many cases the demand of the customer is for properties which are not

produced by the same type of beating, as, for example, high bursting and tearing strength in

the same sheet. This, together with the necessity for operating paper machines at high speed

in order to make enough product to produce a profit, make the problem of beating a very

complicated one which is not simplified by the fact that our knowledge of beating consists

largely of a collection of diverse personal opinions.

The beating of the fibers, which has just been described, is only a part of the

preparation of the stock for use on the paper machine. There are a number of other factors to

consider, such as the addition of fillers, sizing agents, coloring matters and wet strength

agents, and these materials are usually, though not always, added to the fibers in the beater.

The paper and paperboard industry in Malaysia grew from 1.6% to 35% from 1993 to

2000. The growth highlights the potential of using the 26.2 millions tonnes of oil palm frond

(OPF) for pulp and paper production. The research has indicated that the chemical

composition of OPF fibers lie between that of hardwoods and that of straws and grasses. OPF

fibers can easily be pulped using the chemical process, producing pulp and paper of better

properties than most hardwoods pulps. This research also highlights the beating effect in

terms of the fiber morphology, paper strength and properties.

A P.F.I Mill used to beat the OPF pulps. The beaten pulp was made into fiber network

for morphological measurements and the stocks were tested for freeness and drainage time.

Handsheets were made from pulp samples taken at different times during the beating process

and standard physical test were carried out to give refining curves. The fiber length and


35/39

diameter decrease with the degree of beating cause of the fragmentation. The soda pulp also

gives the effect on drainage time which is increasing with the degree of beating. The content

stock freeness (CSF) is decrease with the degree of beating cause of increasing the surface

area to absorb water of fine fiber. The high degrees of beating give the strength paper which

showed in burst and tensile indices. The study showed that beating effect of soda-AQ pulp

produced pulp with different fiber morphology, strength and paper properties

Freeness is a measure of the drainage resistance of a pulp slurry. In the Canadian

Standard Freeness (CSF) test, one liter of dilute slurry (0.3% consistency) is drained through

a standard screen which captures the fibers to form a mat. The amount of water overflowing aweir and collected from a side orifice is then a measure of how fast the water drains through

the mat. CSF values may be as high as 750 ml for an unrefined, unbleached softwood kraft,

and as low as 30-40 ml for a fine groundwood mechanical pulp.

Stock prep refining of kraft pulp will typically reduce freeness to between 600 and 250

ml depending on the starting freeness and the paper grade being produced. Freeness is a good

general predictor of sheet density and, as such, is routinely used to predict strength, opacity

and other physical properties of paper. Freeness is the most widely used control test in the

stock preparation area of the paper mill, at least in North America. Other standard measures

of pulp drainage include Schopper-Riegler (SRo), Williams slowness, and TAPPI drainage

time. All of these measures can be roughly converted to equivalent CSF values.

Drainage of unrefined pulp which is measured as freeness can give an indication on:

i) Fiber Length of pulp, as long fiber pulps have more freeness compared to short fiber

pulpsii) Damage to fiber during pulping, bleaching or drying as short fibers or fines produced

during pulping operation, reduces pulp freeness

iii) Refining energy required to achieve certain slowness during stock preparation.

Freeness of the pulp is expressed in oSR. A higher value (oSR) of the pulp indicates a

slower drainage of the pulp stock. In order to get a good washing, either in brown stock


36/39

washing or in bleaching stages, one needs as low freeness as possible. Therefore, the freeness-

value is a parameter of the drainability of the pulp stock. Drainability is also expressed in CSF

ml (Canadian standard freeness) values. A higher CSF means a higher drainability (easy

dewatering).

Graph Analysis

It seems clear that beating does not affect the strength and structure of paper simply by

increasing interfibre bonding. It was concluded that beating affects paper mainly through

three mechanisms:

Increased fiber segment activation

Increased interfibre bonding

Decreased fiber length

Low-freeness mechanical pulp seems to have as high interfibre bonding as but lower

activation than beaten reinforcement pulp. Therefore, reinforcement pulp beating

improves bonding-related properties such as elastic breaking strain or in-plane

fracture energy only marginally. On the other hand, properties strongly dependent on

activation, such as elastic modulus and tensile strength, are increased by reinforcement pulp

beating.


37/39

.

Fiber straightening is considered as part of the activation effect. In low-intensity

beating, significant fiber shortening occurs only at high refining energy levels. Therefore, in

the earlier phases of beating the first two effects are the most important ones.

Simplified scheme of the beating mechanism. + signifies positive correlation and -negative correlation. Dotted line signifies a weak effect. However, the analysis of activation is

difficult, as there is no direct measurement for fiber segment activation.

CONCLUSION

From the experiment of the standard drainage time against beating time, we can conclude thatthe higher the beating time, the higher the standard drainage time. From the freeness readingagainst beating time graph, the higher the beating time, the lower the freeness reading.


38/39

LIST OF REFERENCES

1. tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdf

2. www.paperindex.com/resources/acronyms/a2e.aspx

3. www.springerlink.com/index/C06536N451KK2774.pdf

4. umpir.ump.edu.my

5. lib.tkk.fi/Diss/2003/isbn9512262797/isbn9512262797.pdf6.7. www.tappi.org/content/tag/sarg/t221.pdf

8. www.springerlink.com/index/C06536N451KK2774.pdf
http://tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdfhttp://www.paperindex.com/resources/acronyms/a2e.aspxhttp://www.springerlink.com/index/C06536N451KK2774.pdfhttp://www.umpir.ump.edu.my/http://www.lib.tkk.fi/Diss/2003/isbn9512262797/isbn9512262797.pdfhttp://www.tappi.org/content/tag/sarg/t221.pdfhttp://www.springerlink.com/index/C06536N451KK2774.pdfhttp://www.paperindex.com/resources/acronyms/a2e.aspxhttp://www.springerlink.com/index/C06536N451KK2774.pdfhttp://www.umpir.ump.edu.my/http://www.lib.tkk.fi/Diss/2003/isbn9512262797/isbn9512262797.pdfhttp://www.tappi.org/content/tag/sarg/t221.pdfhttp://www.springerlink.com/index/C06536N451KK2774.pdfhttp://tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdf


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9. ubs.acs.org/doi/abs/10.1021/ie50292a023

10. tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdf

11. www.science.cmu.ac.th/journal-science/342_PreliSuphat.pdf

12. www.indiapaper.com/contentpages/reliance.cfm

13. cmuj.chiangmai.ac.th/PDF/CMUJ%202005(4)%20vol%202.pdf14.
http://www.ubs.acs.org/doi/abs/10.1021/ie50292a023http://tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdfhttp://www.science.cmu.ac.th/journal-science/342_PreliSuphat.pdfhttp://www.indiapaper.com/contentpages/reliance.cfmhttp://www.cmuj.chiangmai.ac.th/PDF/CMUJ%202005(4)%20vol%202.pdfhttp://www.ubs.acs.org/doi/abs/10.1021/ie50292a023http://tappi.micronexx.com/JOURNALS/PDFS/92MAY139.pdfhttp://www.science.cmu.ac.th/journal-science/342_PreliSuphat.pdfhttp://www.indiapaper.com/contentpages/reliance.cfmhttp://www.cmuj.chiangmai.ac.th/PDF/CMUJ%202005(4)%20vol%202.pdf

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