April 16, 23, 30, May 14, 21, 28, and June 42013

Biomaterial and Biomaterial Science

Bio-Material Science
Toshiharu Enomae
Professor, PhD, Paper Device and Eco-friendly materials

What biomaterial isMaterials constituting components and thestructure of organisms processed to provide
properties required for the use such as:
Wood, paper,
paper, cellophane, rubber,
rubber,leather, polylactic acidpolylactic acid

2G103, 10:10-11:25, Tuesday

Biomaterial Science（Schedule）#

Date

Content1

4/16

History of papermaking

2

4/23

Pulps – Beating and fiber properties

3

4/30

Pulps – Additives and functions-

5/7

No class (Substitute Monday classes)

4

5/14

Papermaking processes & interfiber bonding

5

5/21

Paper– Structural and absorption properties

6

5/28

Paper– Mechanical and optical properties

7

6/4

Recent trend of paper science and technol.

8-10

6/11, 18, 25 Pulping science and technology by Professor Hiroshi Ohi“Paper” －Definition“A thin, flat material obtained by sheetforming and drying fibers especially ofplants”“A thin, flat material made from crushedwood or cloth used especially for writing
and printing on and in packaging” -What biomaterial science is
Science and technology for providing highperformance to biomaterials

Lecture information and contact
Homepage of “Biomaterial Science (T.
Enomae)”http://www.enomae.com/→ Handouts in lecture(講義資料)
E-mail address→ t@enomae.com
for any questions and visit to laboratory

Scope of Paper Science
Colloid Sci（Fiber dispersion system）+ Applied Paper Sci
Colloid Science
Fiber dispersion

Silviculture・ Wood Chem・
Biotechnol. Pulping
Digestion

Pulp
ForestChip

Cambridge Dict.

Applied Paper Science

Plant fibers, especially wood-sourced, as araw material of paper are called “a pulp”

Printing, Packaging

Calendering

Bleaching
CoatingDrying

Press

Wire

Inlet

1

April 16, 23, 30, May 14, 21, 28, and June 4

Who has affected you most?
“Who has affected you most in your life so far?”
was voted in an internet site.
Jesus Christ received the second largest
numbers of votes
Ts’ai Lun（蔡倫）received
the largest.
(A)
Without paper, printing technology would nothave developed, nor would wealthy life today beguaranteed.

2013

Origin of paper
Ts’ai Lun is traditionallyregarded as the inventor of
paper. Exactly, however, heinvented the composition for
paper along with thepapermaking in A.D. 105.
The fibrous materials used inthose day were bark, hemp,
silk, and fishing net.

Origin of paper

MoscowEngland

The world oldest paper
found in that is
estimated to be between
179 and 142 BC (earlyWestern Han 漢朝).
It was used as a map,
where mountains,
Fangmatan（放馬灘）paper
waterways and roads
are drawn.

History of papermaking tech. -Materials
Hemp （ Cannabis大麻・ Linen亜麻）Cannabis has been used for cloth andfishing net in China and Japan.
Linen in Europe.
Hemp
Rags
Recycling of cloth woven originally from hemp. Cotton
from the age of Industrial Revolution
Bast (skin) fibers, such as Paper Mulberry etc.
Wood, capable of producing on a large scale
Kenaf
A kind of hemp promoted for forestry preservation, but
not accepted any more.
Plastics, synthesized paper from polypropylene called “Yupo”

USA

蔡倫

Westward and eastward from China

Nuremberg 1390
Fabriano
1276

Samarkand

BaghdadTs’ai Lun 105

Improvement of paper Japan 610

Spread of papermaking technology

Origin of Printing technology
Gutenberg (1395? –1468)
invented a printing press in around
1445.
The invention consisted ofmass-producing movable type;oil-based ink from linseed oil; anda wooden printing press similar to
the agricultural screw presses
and allowed the mass production of
printed books and was economically
viable for printers and readers alike.

Johannes Gutenberg

Movable type2

April 16, 23, 30, May 14, 21, 28, and June 442-line Bible (42B)
Gutenberg printed andpublished 180 copies of
42-line Bible.
The start of the age of theprinted book in the West

Relationship with paper
Increased paper demand
Development of mass production of paper
Use of wood as a papermaking material
Invention of paper machine to produce“continuous paper”.

2013

The Greatest Inventions of the Past 2000 Years
Edited by John Brockman and published on Jan 12, 2000
John Brockman, a novelist of USA, asked “What is the mostimportant invention in the past two thousand years? and Why?”
to famous.
“Reading glasses” and “eraser” were unexpectedly proposed.
Many people including Dr. Philip Anderson, a Nobel prize
winner, chose “printing technology” because it promoted
knowledge occupied by privileged people to the public.
Another physical scientist chose “watch” for quantification oftime passage that was dependent on one’s sense so far.
“Heliocentric theory”, “mathematics”, “differential and integral
calculus”, “democracy”, and “religion” were also supported.

See http://www.edge.org/documents/Invention.html

History of papermaking tech. – Machine

Mechanical pulping－Groundwood pulp

1670 Hollander beater invented [Holland]
1719 Reaumur submitted his invention - paper can be madefrom wasp hives- to the Academy [France]
1798 Louis-Nicolas Robert invented manufacture of continuous
paper [France]
1844 Keller invented ground wood pulp [Germany]
1851 Burgess [USA] and Watts [England]invented soda pulping
to make wood pulp.
1856 Healey received a patent of corrugated [England]
1856 Tilghman invented the sulfite pulping [USA]1879 Dahl invented Kraft pulping [Germany]
1950 Hardwood pulping initiated[Japan]
1968 Thermo-Mechanical Pulping (TMP) Developed[Sweden]
1977 Quinone-added pulping invented [Japan]

GP or SGW ([Stone] Groundwood Pulp)
Keller invented ground wood pulp in 1844

Old printed material in JapanThe world oldest printed material

In 764, Emperor Koken
had holy texts (無垢浄光陀羅尼経) printed on paper
one million copies forpeace of Japan, containedin one million wooden
miniatures of a three story
tower, and laid out in theten great temples like
Horyu-temple and Todaitemple.

In 1966, printed holy
texts was discovered in
the Buddha tower of
Bukkoku-temple (仏国寺)
of Keishu, Shinra (新羅慶州), currelty Korea(韓国).
This tower is known tohave been built in 751.

3

April 16, 23, 30, May 14, 21, 28, and June 4

2013

The world oldest printed material

世界最古の印刷物

Paper with holy texts (華厳経)
written in 755, Silla era (新羅)was analyzed.

755年に新羅時代の華厳経が書かれた紙

Production of paper and paperboard

Paper Industry of Japan

120

Bankruptcy of Lehman Brothers Great East Japan Earthquake

USA
China
Japan
Germany
CanadaFinlandSweden
Korea
BrazilIndonesia
India
Thailand

100

30

From 2004

25
‒7.8%

20
15

Paper board
Paper

10
‒17.8%
5

Production , million ton

Production amount, million ton

35

80
60
40
20

0
0
Year

1999 2002 2003 2004 2005 2006 2007 2008 2009 2010 20114

April 16, 23, 30, May 14, 21, 28, and June 4

How to make paper

2013

From “wood”

Wood tissue－cells of beech tree

ForestWaste paper

Wood(thinned out)

Component of
hardwood tissue
Vessel20%
Wood fiber

60％

Axial
10％
parenchyma cell
Radial10％
parenchyma cell

Chip
Pulp

Paper

Wood tissue－structure of cell wall

Kind of pulp

S3 layer

Pulp

Cellulose microfibril

Fibers mainly consisting of cellulose
extracted from plant such as wood bymechanical or chemical treatment(Secondary cell wall - 3rd layer )S2 layer(indicated by parallel lines)

Mechanical pulp [MP]Fibers extracted from wood by crushing

S1 layer

Chemical pulp [CP]Primary wall

Middle lamella

Fibers extracted from wood by dissolving lignin

Deinked pulp [DIP] (recycled pulp)
Fibers extracted from waste paper by removing ink

Structure of plant cell wall and axial direction of cellulose microfibrils

Chemical pulp－Fiber geometry
Softwood pulp fiber

Copy paper
consists ofpulp fibers(B)

Observe pulps

wood

Hardwood pulp fiber

Wood composition－Major 3 components
Chemicalcomponent

Approx. ratio (%)

Hardwood

Softwood Hardwood

Cellulose

Cellulose

45

45

Hemicellulose

25

30

Lignin25

20

OthersTerpenoid
Resin acid
Fatty acid
etc.

45 %

Hemicellulose
30 %Lignin2-8Bleached
kraft pulp
40 %

20 %

10 %
2%

Others5%

Change of Compositionby kraft pulping5April 16, 23, 30, May 14, 21, 28, and June 42013

Form of pulp

Disintegration - Separation into individual fibers
Slush pulp
Pulp suspension withconcentrations of approx.
1-4%
Lap pulp
Pulp Formed and folded bywet machine. Called “Drylap” when dried

Dry lap pulp

Dry lap pulp

Dispersed in water ( (D) pulp)

Bale pulp
A bunch of pulp sheets
compressed and boundwith a wireTransported (C) pulp

Standard disintegrator (defibrator)
Pulp is put in water in steel
container with ca. 3.4 L capacity
Stirred with a propeller mixer at
3000 min-1（rpm）
Latency of MP should be
removed at high temperature（Latent=hidden）
Pulp
ChemicalDry Water Revolmass volume utions
30 g
2.0 L 30,000

Mechanical

60 g

2.7 L

Beating (refining)
Post-disintegration process
Process where shear stress is applied
to water-containing fibers resulting infibrillation (formation of small
filaments or fibers) on the surface
and concentrically loose structure

60,000Beating (refining)
Beating achieves large bonded area
between fibers and thus higher paper
strength.

Difference between disintegration and beating

Disintegration is a process toseparate fibers bonded orentangled, keeping fiber
characteristics
Beating is a process to treat
mechanically individual fibers,changing fiber characteristics

Q. Why can this breaking process increase paper strength?

6April 16, 23, 30, May 14, 21, 28, and June 42013

Beater－PFI mill (beating)Beater－Refiner(refining)
Processed by refiner
Rotor

In

Out

Motor
Blade
Disk plate
StatorOut

Rotor
Pulp slurry flow Stator

Beating － mechanism

Refining－movie－refiner

Effect of blades on pulp fibers during beating

Beating－change of fibers－external fibrillation

Beating－change of fibers－internal fibrillation

External fibrillation

External fibrillation

Internal fibrillation

Internal fibrillation＝Concentric loosening(Lamellar separation)
Connection of small
pores formed by lignin
removalScanning Electron Micrographs of freeze-dried
softwood pulp fibers after beating

Lamellar separation offiber cell wall by beating

7

April 16, 23, 30, May 14, 21, 28, and June 42013

Evaluation of fiber properties

Beating－change of paper structure

Freeness (Drainability)
Specific surface area
Fiber length distribution
Distinguishment by staining
Fiber coarsenessCurl index
Unbeaten (left) and beaten (right) softwood pulp sheets
Q. How did fibers and sheets change by beating?

Evaluation of FreenessEvaluation of Freeness

Canadian standard freeness

Canadian standard
freeness（mLCSF）

Unbeaten pulp ca. 650 mL CSF
Beaten pulp ca. 400 mL CSF
Reasons why freenessby(E)
beating areMore fines (small pieces of fibers)
Fibrillation
make paths between fibers in a pulp
mat thin, winding, and long.

One L of pulp
suspension at 0.3%
and 20 ºC is pored andthe volume (mL) of
water drained from theside pipe is measured.
Q. Does CSF increase or
decrease by beating?

Nitrogen adsorption method

Water Retention Value (WRV)
Mw : Mass of pulp after centrifugation
Md : Mass of the pulp after oven drying

WRV(%) =100×(Mw－Md)/Md
Q. Calculate WRVs to 2
decimals in percentage.

SampleBleached softwood

Langmuir model
WRV, %
102

Bleached hardwood

101

TMP

139

CTMP (hardwood)

122

Pulp After cent.(g) Oven dried(g) CTMP (50% HW + 50% SW)
Unbleached sulphite
SBKP beaten
0.61
0.23

124
104

SBKP unbeaten 0.59

0.28

Recycled pulp

HBKP beaten
0.54
HBKP unbeaten 0.45

0.22
0.24

Non-wood pulp

159
204

Never-dried Kraft pulp

114

All the adsorption sites areequivalent and the surface ishomogenous.
Monolayer coverage
No interactions between
adsorbate molecules on adjacent
sites

8

April 16, 23, 30, May 14, 21, 28, and June 4

Nitrogen adsorption method

2013

Nitrogen adsorption method

Langmuir model (cont’d)

Nitrogen gas(N2)

The fractional coverage of the surface θchanges at the adsorption rate
proportional to gas pressure p and thenumber of empty sites N(1-θ).
The desorption rate proportional to Nθ.
Nitrogenmolecule

Material surface

SampleUnbleached Spruce KP
Bleached Spruce KP
Solvent
Spruce α-cellulose
exchange
Spruce GP
Birch KP
Evaporation Unbonded pulp fibers
at 105 °C
Paper
KP=kraft pulp, GP=ground wood pulp

Liquid nitrogen(Coolant)

Adsorption
site

Specific surface area (SSA)
DryingmethodPaper
specimen

Length and width of fibers

BET SSA, m2/g

Softwood tracheid

230
185
185
25
129
1.2
0.5 ̶ 1.0

Hardwood fiber
Hardwood vessel

1 mm

Fiber length and width distribution

Fiber length and width distribution
CCD camera
0.5 mm
Water

Water

Fiber tester, ABB(L&W), Sweden

9April 16, 23, 30, May 14, 21, 28, and June 4

Fiber length and width distribution

2013

Fiber length and width distributionlWidth =

Projected area A
True length L

Shape factor =(Linearity)

Example of captured image

Projected length ℓTrue length L

Mean fiber length

Mean fiber length

Comparison in fiber length between shredded
and unshuredded copy papers

Copy paper

40
Shredded

ShredderRatio (%)

Measurement
Unshredded

20

Unshredded

2.06 mm100Dispersed
in water

Effect of beating on paper properties
Light scattering coefficient,, m2/kg

Specific Surface Area on Light Scattering
Coefficient

1

2

4

5

6

7

Effect of beating on paper properties
Beating decreased Wet Fiber Flexibility(WFF)
Bending strengthof single wet fibers
was measured for
determination of
WFF.
SR = SchopperRiegler method for
determination ofdrainability

BET surface area, m2/kg

3

Fiber length (mm)Wet fiber flexibility, 1/Nm2

5 mm wide each

Beating
increasedinterfiber
bonding area.

1.76 mm0

Shredded

LSA decreases asfiber bonding area
increases.
Interfiber bondingarea can beevaluated by SSA.

30

Beating degree, SR-number

10April 16, 23, 30, May 14, 21, 28, and June 42013

Effect of beating on paper properties

Beating increased Density and Modulus of
Elasticity (MOE)

Beating increased Stretch at Break (SAB) tocertain degree

F=kx

2x

SAB increased
with as well, butleveled off.

Elastic modulus, GPa

Linear relationshipbetween density
and MOE
regardless ofbeating degree

Low beating degreek; sprint
constant
= MOE

x
F
2F

Density, kg/m3

Stock preparation－ additives

Stretch at break, %Effect of beating on paper properties

Density, kg/m3

High beating degree

Additives－size and filler

Paper quality control

Acidic paper

Size (sizing agent) - water repellency
Filler - brightness and opacity
Strength agent – dry or wet strength
Dye – optical brightening agent (OBA)

Paper manufacturing control
Retention aid – ex. aluminum sulfate –fines, fillers, and size retained more
Aintiseptic (preservative)

Size (sizing
agent)

Non-acidic paper

Rosin（Abietic acid) Alkyl ketene dimer （AKD）,
Alkenyl succinic anhydride（ASA）
Alminium sulfate
Cationic polymer such as(alum),Polyamine-amide
deteriorates paper epichlorohydrin (PAE)
Clay, Titan dioxide, Calcium carbonate, Titan
TalkdioxideRetention
aid
Filler

pH at
4.5～5.5
papermaking

7.5～8.5(7 or slightly greater)

Q. Why is calcium carbonate not used for acidic paper?

Additives－size and filler
Rosin (abietic acid)

Additives – deterioration of acidic paper
AKD

Aluminum sulfate deteriorates paper.
Al２(SO4)3 + 2H2O → 2Al(OH)2+ + 2H+ + 3SO42CH2OHO
OH+[ C (CH 2)4 C NH (CH 2)2 N (CH 2)2 NH ]n
O

O

ASA
PAE

O
H

O

CH2OH
O
OH

+ H2O
O

OH

OH

CH2OH
O OH, H
OH

CH2OH
H
O
OH
HO
OH

OH

O

Acid hydrolysis↓
Deteriorationof paper11

April 16, 23, 30, May 14, 21, 28, and June 42013

Papermaking – Additives - movie

Additives－size and filler (2)Acidic paper

Non-acidic paper

Strength Cationic polyacrylamide(C-PAM)
resin

CH2OH
O
OH

CH2CH n CH2CH
C=O

C=O

NH2

O

Cationic starch

O

CH3
O
CH2-CH2-N+-CH3

CH3

CH2-CH2-N+-CH3

CH3

CH3

Cationic polyacrylamide

Cationic starch

Papermaking - wire section

Papermaking－approach section
Pressurized screen Head box

Twin-wire machine

Fourdrinier machine

Wire (Fourdrinier )Centrifugal cleaner

白水 waterWhite

Secondary screen
Secondary cleaner

Fanpump Wire
pit

Felt

Inlet

Beaten pulp
Broke
Additives

Machine
chest

Paper
product
Broke

RecycleWeb
CylinderMarkets
Consumers
Waste
paper

Cylinder machine

Q. What is a merit of
Cylinder machine?

Papermaking – (wet) press section

Papermaking – dryer section

A wet web is pressed at high pressure
between large rolls to squeeze out excesswater.
Water transfers to felts that sandwich thewet web.
Pressing increases
density and wet web
strength.
The common numberof nips is 3 or 4.

Steam-heated cylinders dry the paper withcanvases.
Free water evaporates, between fibers first , inside
fibers second, and between fibrils last .
At less than 9 % moisture content, bonding water
evaporates, forming interfiber bonds.

Paper
Canvas (felt)

Drying cylinder
for felt
DryingcylinderPaper

Canvas (felt)

Kodak Historical Collection #003 (1986)

12

April 16, 23, 30, May 14, 21, 28, and June 42013

Papermaking – calender section

Soft nip calender

Gloss improvement and compression of paper
Linear pressure at nip:

Number of passed nips

Thickness decrease ratio, %Supercalender

Papermaking – calendering effect

Paper gloss, %A number of rolls press the passing paper.
They make the paper surface extra smooth and glossy
with friction, and provide a higher density and more
uniform thickness

Basepaper

Coat layer

Number of passed nips

The number of nips is occasionally more than 10.
Q. Why is it as many as 10 although only 3 or 4 for wet press?

Types of chemical bondIonic bond = a chemical bond in which two ions are joined
together because one has a positive charge and the other anegative charge
Covalent bond = a chemical bond in which two atoms share
one or more pairs of electrons that hold them together (ca.
500 kJ/mol)
Hydrogen bond = a weak connection that is formed between
an atom of hydrogen (= a gas) and an atom of anothersubstance such as oxygen or nitrogen (= a gas) （10～40
kJ/mol）
Van der Waals forces = the relatively weak attractive forcesthat act on neutral atoms and molecules and that arise
because of the electric polarization induced in each of theparticles by the presence of other particles
Dipolar bond (coordination bond)
Metallic bondInter-fiber bondInterfiber approach and hydrogen bondformation due to water evaporation
Cellulose surface

H-O-H

H-O-H

H-O-H

H-O-H

Cellulose surface

Loose hydrogen bond mediated by water

Firm hydrogen bond with a water monolayer Direct hydrogen bondInter-fiber bondEffect of water on interfiber bond formation
Q. Suppose twocrossing flat fibers withthe square , length L ona side at the crossing
point. As they dry andthe interfiber distance dcomes to 1 mm, Howmuch contraction stressdevelops between thetwo fibers?

Fiber

L µm

Fiber

d µm
The attractive force iscalled Campbell force.

Inter-fiber bondEvidence of hydrogen bond
When paper mass was measured after allowing tostand in deuterium water (D2O) vapor until
saturation, 0.5 to 2.0 % of hydrogen of all thehydroxyl groups was not replaced with deuterium.
This ratio corresponds to the percentage ofhydrogen bonded hydroxyl groups.
Energy required for tensile breakage was calculated.
19 kJ/mol (equivalent to hydrogen bond energy)
Strength decreased with acetylation of carboxylgroupsCell-OH → Cell-O-C-CH3
O

13

April 16, 23, 30, May 14, 21, 28, and June 4Inter-fiber bond

2013

Inter-fiber bondEffect of cell wall thickness on wet fiber flexibility

Effect of fiber flexibility on Relative Bonded Area

Bonding ratio, %Cell wall thickness, µm
8.8 µm

4.7 µmFiber flexibility, 1/Nm2

Forming (Wire section) － Moisture content
HeadboxSlice

Post-forming－Size press
SizingInternal sizing- addition to pulp slurry
External (surface) sizing – application to surface

What is surface sizing (size press)?
Size press

Couch rollWiresection
Pulp
1%
Moiture99 ％PresssectionCalendersectionDryer section

The treatment for providing water-resistant property
to paper by application of starch solution etc.
Other than starch, carboxymethyl cellulose, polyvinyl
alcohol, polyacrylamide etc. are applied. Strong
water-repellency is not required.

20 %

40 %

95 %

Advantages over internal sizing

80 ％

60 ％

5％

100% retained. No deposit on walls of former or frothPost-forming－Size press

Pigment coating

Purpose andeffectPicking prevention
in offset printing
Ink jet printability
to prevent
bleeding

Pigment
BinderWater
Dispersion / Mixture

Blade coater etc.

14

April 16, 23, 30, May 14, 21, 28, and June 4

Coated paper surface -2013

Drying and processing – movie

Scanning Electron Micrograph

Basepaper
surfaceCoatingsurface

To increase smoothness, brightness,
opacity, and gloss, and control liquid
penetration

Paper properties –Fundamental and applied properties

23 ºC 50% RH (Relative Humidity)

Conditioning
Structure
Surface chemistry
Liquid absorption
Mechanical properties
Optical properties

Paper properties depend on
humidity, but less on temperature
although temperature differenceby more than 10 ºC changes ex.
tensile strength significantly.

Moisture content (%)

Conditioning and test atmosphere

50 humidity% r.h. (%)
Relative

Conditioning and test atmosphere

Hysteresis
Dry paper to half
the equilibrium
moisture content
and back to 50%
RH for testing
Moisture content
is affected by
crystallinity

Paper structure – basic properties
Grammage (g/m2)
Mass (g) per square meter at 23 ºC and 50％RH
Grammage（（oven-dry basis）） is based on theconstant mass attained when kept at 105 ºC

Thickness (mm)Single sheet thickness, distance between twoparallel planes holding a sheet at 100 kPa
Bulking thickness, thickness per sheet,calculated from that of 10 superimposed sheets
Includes surface roughness (dents)

15

April 16, 23, 30, May 14, 21, 28, and June 42013

Paper structure – basic properties

Paper structure – basic properties

Density（grammage/thickness） affected by grammage!?

Q. Which is higher, single sheet thickness or
bulking thickness?

Apparent thickness, µm

140

Density
Mass per unit volume in g/cm3 calculated fromgrammage divided by thickness

120
100
80
60

Sheets prepared fromsoftwood bleached kraft
pulp beaten moderately

40
20
0
0

20

40

60

80

100

Grammage, g/m2

Paper structure – thickness measurement
Micrometer

130
Thickness by Hg buoyancy, µ m

Mercurybuoyancy
methodPaper structure – Why is the thickness
different between the two methods?

0.5 kgf/cm2-1 min
3.5 kgf/cm2-5 min
7.0 kgf/cm2-20 min

120

Filter paper side

110
100

Laboratory sheet
90
80

Micrometer
thickness

Beaten hardwood kraft
70
70

80

90

100

110

120

Metal plate side

Mercury B
thickness

130

Thickness by micrometer, µm

Paper structure – Factors affecting density

Paper structure – Factors affecting density
Wet press and calendering

0.8

0.8

0.7

0.7

Density, g/cm 3

Density g/cm 3

Beating and filler loading

0.6
0.5
0.4

Beating rev. (PFI mill）

Calcium carbonate addition

0.6
0.5
0.4

Wet press

Calendering- linear pressure

16April 16, 23, 30, May 14, 21, 28, and June 42013

Paper structure-Scanning electron microscope(1)Paper structure-Scanning electron microscope(2)100 µmCopy paper

Newspaper

Paper structure – Smoothness
Air leak method
Air flow rate through a gap between paper
surface and smooth metal plate

Surface profile (Microscopy)
Measurement method
Stylus profilometry
Scanning Probe Microscope
Confocal Optical MicroscopeInterferometric Optical Microscope
Multi-detector Scanning Electron Microscope
Expression of surface roughness

Paper structure – Smoothness

100 µmJapanese paper

Tissue paper

Paper structure – Smoothness
Air leak method
Air flow rate through a gap between
paper surface and smooth metal plate

Surface profile (Microscopy)
Surface shape measured using
profilometry such as stylus profilometry,
confocal optical microscope.
Several ways of expressing surface
roughnessPaper
structure
紙の構造-平滑度– Smoothness

Air leak method

Theory of air leak method

Print surf roughness (µm)
Bekk smoothness, Oken smoothness (s)Hagen-Poiseuille flow

Parker Print-Surf (a slab)
Measuring head
Paper
Oken type (circular tubes)
Backing rubberπ∆P r 4Q=
8µ l
Q: volumetric flow rate
∆P: pressure differenceµ: dynamic viscosity
r: radius of tube
l: length of tube

y

x
x
rθ

z

Q: flow rate inz direction

17

April 16, 23, 30, May 14, 21, 28, and June 42013

Paper structure– Smoothness
紙の構造-表面形状測定

Paper structure – Air permeance

Surface profile can be measured in 2D or 3D.
Stylus, light beam, electron beam, or probe

MethodCenterline average roughness(arithmetic average)

Ra =Air permeanceP [mm/(Pa･s)]

Gurley tester
A:642 mm2
Airtester∆pOken

1 l
y dy
l ∫0

P=

Universal
air permeance

Root mean squared roughness

RMS =

1 l 2
y dy
l ∫0

t: permeation = Air resistance(Gurley)time (s)V: 100 mL

Paper structure –Air permeance of coated paper
0.5
Air permeance, µm/Pa･s

Oken smoothness, sPaper structure –Smoothness of coated paper
450
400
350
300
250
200
150
100
50
0

V
1000 × A ∆p t

After calendering
Basepaper
Before calendering

0

5

10

15

20

0.4

Before calendering

0.3
After calendering

0.2
0.1
0
0

5

[
] Unevenness sensed visually when
white light is transmitted through paper – STD or
CV of optical density
Transmitted light I 0  I1 I2 …
log Mass
B1 B2 …
 In 
[]Distribution of
local mass Bn –STD or CV ofPaper I0 I0
local mass
Irradiating light
STD=Standard deviation, CV= coefficient of variation

20

Paper structure - Formation
Time until dehydration (s)Transmitted lightimages of softwood
pulp sheets
Formation becomes
(F)
worse
by cationicpolymer addition
and increased time
until dehydration
Cationic polymers
increases fiber
retention.

Cationic polymer
P:Added
N:Nonadded

Formation

15

Latex content, pph

Latex content, pph

Paper structure - Formation

10

10

120

HN10

HN120

HP10

HP120

18

April 16, 23, 30, May 14, 21, 28, and June 42013

Interaction- between paper and water (liquid)

Surface chemistry - Contact angle
Contact angle (θ)

Wetting
Contact angle
Surface energy
Sizing degree
Liquid penetration
Swelling

The angle made by the solid and liquid surfaces
when a liquid droplet is placed on a solid
surface.
When 0º< θ < 90º, “wetted” and when θ>90º
γL“unwetted”.

Young equation

θWhen the contact angle
is constant, horizontal
components of forces
are balanced.

γsγiγi － γs ＋ γL cos θ ＝0

Surface chemistry - Contact angle

Surface chemistry - Contact angle

Contact angle on a rough solid surface

Wenzel’s equationLcosθ w = r cosθ

θw
γi

θ
γs

cos θ w = r cos θ180
r=1 の場合

150

見かけの接触角θw

Supposed that the area including
microscopic structure is r times larger
than the apparent one,
Wenzel’s contact angleγ

On a rough surface,when θw ＜ θ at θ ＜90º, easily-wetted
surfaces become
more easily-wetted.
But, when θw ＞ θ at
θ ＞ 90º, hardlywetted surfaces
become more hardlywetted.

r=1.2の場合
r=2 の場合

120

Hardly-wetted

90

60

Easily-wetted

30

0
0

30

60

90

120

150

180

真の接触角θ

Contact angle of paper - Beating effect140

Wet-press: 90 g/m2, 7.0 kg/cm2

Beating and smoothness
Oken smoothness, sContact angle, °

130
120
110
100

5000 Rev beating
10000回叩解

9020000回叩解

80
0

200
400
Contact time, sSurfacessmoothed bybeating
became easilywetted.

Hardwood kraft pulp sheet
20
15
10
5
0

20000 Rev
10000 Rev
5000 Rev

600

Grammage and wet press pressure

19April 16, 23, 30, May 14, 21, 28, and June 42013

Surface chemistry - Contact angle
On composite surfaces

The effective contact angle θC is dependent on
the areal ratio of each component.

Cassie's law

is stated as cosθ C = Q1 cosθ1 + Q2 cos θ 2, where θ1 is the contact
angle for component 1 withareal fraction Q1 and θ2 isθ
the contact angle forcomponent 2 with areal
fraction Q2 (Q1 + Q2 = 1). Component 1 Component 2

Surface chemistry - Contact angle
Q. What is the contact angle θc of sized paper?
Sizing agent need not cover the whole surfaceof fibers for repelling water. If a sizing agent
covers 5% of the whole surface, what is thecontact angle θ ?
Assume that θ is 0˚ for unsized fibers and 120˚
for the covering size.
θc(G) × cos 0º +cosθc = 0.95
(H) × cos 120º
0.05
Paper
cosθc = 0.95 –(I)0.025 = 0.925

Size

(J)
θc = 22.3º

Surface chemistry - Contact angle

Surface chemistry - Contact angle

Q2. What is the contact angle θc of sized paper?
Half the volume of paper is air. If 50% of
paper surface is air, what is the θc ?
Assume that θc of a true surface of sized
paper is 22.3˚ and θ of air is 180˚.
(K)(K)
cosθc = 0.5×cos
22.3º + 0.5×cos
180º(K)(L) + (K)cosθc = 0.5×0.925
0.5× (M)1θc(N)= 0.155

Comparison in Water absorption(O) ºθc = 92.1

Size

Steady flow in a pipe

πPr 4
Q=
8ηl
l: Capillary lengthr: Capillary radius
η: Liquid viscosity
Q: Volumetric flow rate
(Hagen-Poiseulle equation)

Wood-containing paper“wood-containing” means “made from mechanical pulp”

Liquid absorption theory - Capillary model
Force developing arounda meniscus of a liquid ina capillary (pipe)

Parchment

Paper

P=F/S=2γcosθ/r

P

γ

γcosθ
θ

F=2πrγcosθ
F

2πr
S=πr2

θ

Liquid absorption theory - Capillary model
Q. Substitute the relation represented in the figure into
the H-P equation and develop the Lucas-Washburn equation.
H-P equation

2γ cos θrdVdlQ== π(Q)
r2
dt
dt
Substitute

πPr 4
Q=
8ηl

P=

r

dl

dt

2dl
dV = πr(P)rLucas-Washburn equationl=rγ cos θ ⋅ t2η

20April 16, 23, 30, May 14, 21, 28, and June 42013

Water absorption rate - How to measure

Water absorption rate – How to measure
Calculate transferred volume per unit area Vt

Bristow’s apparatus
A liquid supply head filled witha liquid of volume V scans
paper at various speeds v.

L

1 mm (b)
Paper
moves

15 mm (w)V

Contact time t = b / v
Scan speedv
Slid widthbTransfer Vol Vt=V/(wL)
Liquid volume V
Slit widthw
Trace lengthLv

Vr Roughness index
T Contact time
Tw Wetting delay
Ka Absorption coeff.
For oil, Tw = 0.
Then,

Vt = Vr +(Q)
Ka T

Transferred liquid volume, ml/m2

Vt = Vr + K a T − Tw

Oil A

Vt

V
Contact time t = b/v
Scan speed v
Slid widthbTransfer Vol Vt=/V (wL)
Liquid volume V
Slit widthw
Trace length L

Water absorption rate - How to measure

Water absorption rate – Water and oil
For water,w

Vt

Automatic Scanning Absorptometer（Spiral-scan Bristow’s apparatus）

Oil B

To meniscus
detector

Scanning speed changes stepwise during
measurement

Water supply
head

1 mm

Water

5 mm
Infrared sensor
Glass capillary

Ka
Vr

Bristow’s plot of kraft paperTw

Meniscus

Contact time, s

Step motor

T

Water absorption rate of ink jet paper -ASA

ASA

Mechanical properties –Tensile strength
Load-elongation curve
Method15 mm in width
100 mm in span
10 mm/min elong speed
Tensile index I

40

F

No.2
No.3

30

20
・インキが転移しなかった部分のデー
タ点、明らかに誤ったデータ点を省略
してプロットした図・No.1と2は、ほぼ同じ傾向のインキ

10

0
0

5

10

Square root of contact time, (ms)1/2

15

Limit ofelasticity

Load, N

Volume of INK transferred, mL/m2

No.1

∆F
:

:

Strain at break εT∆LiElongation, mm

εT

∆L

∆

Modulus of elasticity E*

E*

∆
∆

:

21

April 16, 23, 30, May 14, 21, 28, and June 4

2013

Mechanical properties –Tensile strength

Anisotropy–Tensile strength
12

Plastic region

Elongation, mm

Compressive
force

Elastic region

Fiber

MD

8
Unbeaten kraft

6

Copy paper

CD

4
2
0

Elastic elongation of fibers
Elastic elongation of fiber
network

0

1

2

3

4

5

6

7

8

Elongation, %Microcompression

Anisotropy–Tensile strength

Mechanical properties – Stiffness

12(Bending) stiffness S represents the degree to which
paper resists bending
S=EI

10
Load, kgf

Unbeaten kraft paper (89.4 g/m2)
Copy paper (64.4 g/m2)

10
Load, kgf

Load, N

Extension of curl
Extension of microcompression
Breakage of interfiber bonds
Breakage of fibers

8

Light-weight coated paper(64.9 g/m2)
Newsprint paper(46.4 g/m2)

MD

Light-weight coated paper
Newsprint paper

CD

S=Mr

6
4

E is Young’s modulus
I is area moment of

M is bending
momentr (m)inertiar is radius ofcurvature

2
0
0

1

2

3

4

5

6

7

8

M (mN⋅m)

M

Elongation, %Q. Why does light-weight coated paper elongate greatly?

Mechanical properties – Stiffness
Taber Stiffness

Mechanical properties – Folding endurance
Folding endurance
logarithm number ofdouble folds at 120˚on both sides thatare required tomake a test piece
breakLonger fibers
tend to show
120˚
higher values.

15˚

Bending moment
when a test piece
38mm wide is bent
to 15˚ and load
length 50 mm
The unit is mN⋅m

1kgf

120˚
MIT tester

Taber tester

22April 16, 23, 30, May 14, 21, 28, and June 4

2013

Lab-on-paper as a medical check-up sensor
Paper substrate
Doctors in HOSPITAL

Capillary force due to porous structure

Data

Diagnosis
Patients at HOME

Liquid transport
designed channel

・decreases the number of patients・shortens hospital stay
→Secure appropriate medical service in hospitalLab-on-paper as a medical check-up sensor
Affordable & easy-to-handle device is required

Electrochemical Lab-on-Paper

Electrochemical Lab-on-Paper
Potentiostat

・Liquid transportation

Electrode・Ink jet・Quantitative analysis

Electrode・Ink jetHydrophobic barrier・Multiple test
・Small amount ofliquid required

Potentiostat

・Liquid transportation

Hydrophobic barrier・Multiple test
・Small amount ofliquid required

・Quantitative analysis

Electrochemical Lab-on-Paper

Paper Preparation
Improve printability
・Decrease pore size→ prevent ink bleeding
・Materials…cotton pulp→almost none of impurities#

Beating(Revolution, PFI mill)Density of paper(g/cm3)

1

10000

0.568

2

20000

0.622

3

30000

0.641

Beating increases paper density

Paper substrate was successfully designed

Potentiostat

・Liquid transportation

Electrode・ Ink jetHydrophobic barrier
・ Multiple test
・ Small amount ofliquid required

・Quantitative analysis

23

April 16, 23, 30, May 14, 21, 28, and June 4

180

2013

UV curable ink for hydrophobic barrier

Microchannel Fabrication

・Polymerized by UV-light irradiation
・Monomers, oligomers, initiators in ethanol → VOC-free

IJ printing

Ingredients of UV ink
O

Paper
O

O

C18H37

UV irradiation

O
O

O

O

Top

Top

Back

Back

C10H20O

Perspective

O

Octadecyl acrylate 1,10-decanediol acrylate
59.5%

Irgacure 819

25.5%

15.0%

Top
(m/m)

Back

Solvent-free & Green Material

Microchannel was successfully fabricatedCitterio, D. et al., Proc. MicroTAS 2011, 2099-2101

Electrochemical Lab-on-Paper

3 mm

Citterio, D. et al., Proc. MicroTAS 2011, 2099-2101

Fabrication Processes of electrodes
Electrodes printed with PEDOT:PSS
Potentiostat

・Liquid transportation

Prepared paper
Micro-channel printed with
UV-curable ink
BMP printed
Enzyme (Glucose oxidase) printed

Electrode・ Ink jetHydrophobic barrier
Enzyme・ Multiple test
・ Small amount ofliquid required

BMP (binder&mediator)
PEDOT:PSS (electrode)・ Quantitative analysis

Lab-on-Paper was successfully fabricated183

Chronoamperometry for Glucose Test

Glucose concentration
Potentiostat

Current value at 0.5 V(vs. printed pseudo reference electrode)

Dispense

2.5
y = 4.90 x + 0.30
R² = 0.98
n=3

Current (µA)

2

1.5

1

0.5

Tested glucose solution
・1 M KCl
・1 M PBS buffer
・Various amounts of glucose

Gluconic acid + H+
Glucose oxidase

0

e-

0

Glucose+O2
186

0.1
0.2
0.3
Glucose concentration (mg/mL)

0.4

Glucose conc. was successfully measured

24