2015/11/10

Biomaterial Science（2015 Schedule）

EG60411

Biomaterial Science
Toshiharu Enomae

Professor, PhD, Paper Device and Eco-friendly materials

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

2015/11/10

Lecture information and contact

#Date

1

10/6

History of papermaking

2

10/13

Pulps – Beating and fiber properties

3

10/20

Pulps – Additives and functions

410/27

Papermaking processes & interfiber bonding

511/10Paper– Structural properties

611/17

Paper– Surface properties

711/24Paper–Wetting and absorption properties

812/1

Paper– Mechanical and optical properties

912/8

Polysaccharide chemistry by Assoc Prof Akiko Nakagawa

1012/15

Recent research of paper science and technology

1112/22

Examination

Content

2015/11/10

Pigment coating Homepage of “Biomaterial Science (T.

Enomae)” http://www.enomae.com/→ Handouts in lecture(講義資料)

PigmentBinder E-mail address→ t@enomae.com
for any questions and visit to laboratory(Bio-Agr. Bldg. 生農C209 or 総合A618)

Water
Dispersion / Mixture

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Pigment coating

Blade coater etc.
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Pigment coating

2015/11/10

Biomaterial Science by Toshiharu Enomae

2015/11/101

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Coated paper surface -Drying and processing – movie

Scanning Electron Micrograph

Basepaper
surfaceCoatingsurface

To increase smoothness, brightness,
opacity, and gloss, and control liquidpenetration
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Paper properties –Fundamental and applied properties

2015/11/10

Conditioning and test atmosphere 23 ºC

 Conditioning Structure Surface chemistry Liquid absorption Mechanical properties Optical properties

50% RH (Relative Humidity)

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

2015/11/10

Conditioning and test atmosphere
Moisture content (%)

 Hysteresis
 Dry paper to half

50 humidity% r.h. (%)
Relativethe equilibrium
moisture content
and back to 50%
RH for testing Moisture content
is affected by
crystallinity

2015/11/10

Biomaterial Science by Toshiharu Enomae

2015/11/10

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)

2015/11/102

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Paper structure – basic properties

Paper structure – basic properties Density（grammage/thickness） affected by grammage!?

 Density

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

140

Apparent thickness, µm

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

1201008060

Sheets prepared fromsoftwood bleached kraftpulp beaten moderately

40200020

Paper structure – Why is the thickness
different between the two methods?

406080Grammage, g/m2

2015/11/10

100

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Paper structure – Factors affecting density
 Beating and filler loading
0.8Density g/cm 3

Filter paper side

Laboratory sheet

Micrometer
thickness

0.7
0.6
0.5
0.4

Mercury B
thickness

Metal plate side

Beating rev. (PFI mill）
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Paper structure – Factors affecting density

Calcium carbonate addition
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Paper structure-Scanning electron microscope(1) Wet press and calendering
Density, g/cm 30.80.70.60.50.4

100 µmCopy paper
Wet press

Newspaper

Calendering- linear pressure
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Biomaterial Science by Toshiharu Enomae

2015/11/10

3

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Paper structure – Smoothness

Paper structure-Scanning electron microscope(2) 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 surfaceroughness

100 µmJapanese paper

Tissue paper
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Paper structure –Smoothness of coated paper

Paper structure– Smoothness
紙の構造-表面形状測定
Surface profile can be measured in 2D or 3D.
 Stylus, light beam, electron beam, or probeCenterline average roughness(arithmetic average)

Ra =Oken smoothness, s

1z dyl ∫0l

Root mean squared roughness

zydy

RMS =

1 l 2z dyl ∫0450
400350300250200150
100500After calendering
Basepaper
Before calendering

051520Latex content, pph 2015/11/10

2015/11/10

Paper structure - FormationPaper structure - Formation
Formation
[] Unevenness sensed visually when
white light is transmitted through paper – STD or
CV of optical density
Transmitted light I 0  I1 I2 …
log MassB1 B2 …
 In 
[]
Distribution oflocal mass Bn –STD or CV ofPaper I0 I0
local mass
Irradiating light2015/11/10
STD=Standard deviation, CV= coefficientof variation

Biomaterial Science by Toshiharu Enomae

Time until dehydration (s)Transmitted lightimages of softwood
pulp sheets Formation becomes(F)worseby cationicpolymer additionand increased time
until dehydration
 Cationic polymers
increases fiber
retention.

10120



Cationic polymer
P:Added
N:Nonadded



10l

HN10

HN120

HP120

HP10
2015/11/10

4

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Surface chemistry - Contact angle

Interaction- between paper and water (liquid)

Wetting Contact angle
 Surface energy Sizing degree
 Liquid penetration SwellingContact angle (θ)
 The angle made by the solid and liquid surfaces

when a liquid droplet is placed on a solidsurface.
 When 0º< θ < 90º, “wetted” and when θ>90ºγL“unwetted”.

Young equationθ When the contact angle

is constant, horizontal
components of forces
are balanced.

γi － γs ＋ γL cos θ ＝0

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Surface chemistry - Contact angle

Surface chemistry - Contact angle

Contact angle on a rough solid surface Supposed that the area including

microscopic structure is r times larger
than the apparent one, Wenzel’s contact angle
γLθwcosθ w = r cosθ

cos θ w = r cos θWenzel’s equation

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

180
r=1 の場合

150

見かけの接触角θw

γsγi

r=1.2の場合
r=2 の場合

120

Hardly-wetted

9060

Easily-wetted

30

0030

60

90

120

150

180

真の接触角θ

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Contact angle of paper - Beating effect

Hardwood kraft pulp sheet140

Wet-press: 90 g/m2, 0.70 MPa

Oken smoothness, s130

Contact angle, °Beating and smoothness120110100

5000 rev beating
10000 rev beating
20000 rev beating

900200smoothed bybeating
became easilywetted.

2015105080400600

 Surfaces

20000 Rev
10000 Rev
5000 Rev

Contact time, s
2015/11/10

Biomaterial Science by Toshiharu Enomae

Grammage and wet press pressure 2015/11/105

2015/11/10

Surface chemistry - Contact angleSurface chemistry - Contact angle
Q. What is the contact angle θc of sized paper?

On composite surfaces

 The effective contact angle θC is dependent on Sizing agent need not cover the whole surface

the area ratio of each component.
Cassie's law
 is stated asof 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

cosθ C = Q1 cosθ1 + Q2 cos θ 2, where θ1 is the contact
angle for component 1 witharea fraction Q1 and θ2 is theθcontact angle for component
2 with areal fraction Q2 (Q1+ Q2 = 1).
Component 1 Component 2Size(J)θc = 22.3º

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2015/11/10

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% ofpaper 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(O) ºθc = 92.1



Steady flow in a pipe

πPr 4
Q=8ηl
l: Capillary lengthr: Capillary radius
η: Liquid viscosity
Q: Volumetric flow rate

Parchment

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

P=F/S=2γcosθ/r

Pγ

2015/11/10“wood-containing” means “made from mechanicalpulp”

2015/11/10

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

PaperSize

F=2πrγcosθFH-P equation

2γ cos θrdVdl
Q== π(Q)r2
dtdt
SubstituteπPr 4
Q=8ηl

2πr
S=πr2

θ

P=r


2015/11/10

Biomaterial Science by Toshiharu Enomae

dt2dl
dV = πr(P)rLucas-Washburn equation

l=(Hagen-Poiseulle equation)

dlrγ cos θ ⋅ t2η

2015/11/106