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Shape Engineered Pigments Based Barrier Coatings for SBS Paperboard. Dr. Lokendra Pal (WMU)* Dr. Margaret Joyce (WMU) Dr. Paul Fleming (WMU) Dr. David Knox (MeadWestvaco) *Now with Hewlett-Packard Company. Discussion Points. Introduction Objectives Experimental Design - PowerPoint PPT Presentation
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1
Shape Engineered Pigments Based Barrier
Coatings for SBS Paperboard
Dr. Lokendra Pal (WMU)*Dr. Margaret Joyce (WMU)Dr. Paul Fleming (WMU)Dr. David Knox (MeadWestvaco)
*Now with Hewlett-Packard Company
2
Discussion Points Introduction
Objectives
Experimental Design
Results & Discussion
Conclusions
3
Introduction Paper and board have very high permeability
i.e. virtually no ability to block diffusion or movement of water and water vapors.
Plastic materials have completely different chemical structures, and can easily be made resistant to water and water vapor transmission.
Hence paperboard packages are commonly extrusion coated off-line with polyethylene (PE), polypropylene (PP) & PET, etc.
4
Introduction Cont’d Consumer pressure to use environmentally
sensitive packaging assemblies has created a large and expanding market for renewable, recyclable and/or biodegradablerenewable, recyclable and/or biodegradable materials.
The need to reduce the amount of non-non-recyclablerecyclable materials is ever increasing.
5
Introduction Cont’d This study is an attempt to limit or replacelimit or replace
the above mentioned technologies with an online alternative; shape-engineered environmental friendly clays.
This will improve the productivity and hence the economics of production, providing the barrier performance of the grade can be achieved.
6
The Structure of Clay Minerals Most clay minerals are part of a large family of
silicate minerals called phyllosilicates.
Two dimensional sheets of
tetrahedrally co-ordinated silica linked to octahedrally co-ordinated alumina or magnesium
1:1- phyllosilicates such as kaolin (china clay)
2:1- phyllosilicates such as MMT and laponite.
7
The Structure of Clay Minerals Cont’d
Tetrahedral Structure
Octahedral Structure
Tetrahedral Structure
Octahedral Structure
Tetrahedral Structure
Tetrahedral Structure
Octahedral Structure
Tetrahedral Structure
Octahedral Structure
Tetrahedral Structure
Tetrahedral Structure
Octahedral Structure
Tetrahedral Structure
8
Clay Minerals Properties
Clay Minerals
Natural Synthetic
Micron<Micron &
Nano>Nano Nano
Kaolin Clay
Shape Engineered
(Kaolin)
MontmorilloniteHectroites etc.
Laponite Clay
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Microcomposites No intercalation or exfoliation Conventional filled polymer
Nanocomposites Complete exfoliation Layered Materials in Polymers
Microcomposite vs. Nanocomposite
Pigments particles size: length (m) width (m) thickness (m)
Pigments particles size: length (m) width (m) thickness (nm)
10
Tortuous Path for a Particle to Migrate Through a Layer of Platey
Pigments Clay platelets provides high tortuosity, hence the effective flow path, (Le ) of the air, water vapor or gas molecules (or atom) is significantly greater than the porous medium length (L).
Effective Flow Length (Le) Actual Flow Length (L)
Substrate
Clay Platelets Water Molecule
Effective Flow Length (Le) Actual Flow Length (L)
Substrate
Clay Platelets Water Molecule
Substrate
Clay Platelets Water Molecule
Substrate
Clay Platelets Water Molecule
11
Objectives To study the influence of shape-
engineered pigments on structural and functional properties of barrier coatings.
To determine if the barrier characteristics of SBS paperboard can be improved by incorporating shape-engineered pigments.
To determine the dependence of barrier properties on pore structure.
12
Experimental Design
This work is divided into four phases:
1. Formulation of barrier coatings using shape engineered pigments
2. Application of barrier coatings onto SBS baseboard
3. Characterization of the barrier and mechanical properties
4. Optimization (future papers)
13
Materials
Binder TypeSolids,
%pH
Viscosity, cps
Avg. Particle Size, nm
A Acrylic54.5- 55.5
7.5 400 250-325
B SBR48.5-50.0
8.0 250 150-200
Mineral PigmentAspect Ratio
Avg. Particle Size, nm
BET Surface Area, m2/g
Kaolin clay # 1 10-20 150-200 20-22
Kaolin clay # 2 50-60 450-550 18-20
Kaolin clay # 3 80-90 950-1050 12-14
Table 1. The Characteristic of the Mineral Pigments
Table 2: The Characteristic of the Binders (Resins)
14
SEM- Shape Engineered Pigments
Kaolin Clay 1
Kaolin Clay 2
Kaolin Clay 3
15
Materials Cont’dTable 3: The Characteristic of the Base Substrate
SubstrateProperties
Solid Bleached Sulfate (SBS), 270 g/m2
Uncalendered(0 PLI)
Calendered (1600 PLI)
Thickness, mils 14.20 (0.45) 12.2 (0.39)
PPS Porosity, ml/min 249.05 (8.52) 84.4 (5.01)
Permeability, µm2 4.33 x10-3 1.28 x 10-3
Roughness, µm 5.90 (0.28) 4.323 (0.19)
Brightness, % 85.33 (0.30) 84.96 (0.21)
MVTR (g/m2day) 1149 (89.01) 1115.46 (81.24)
16
Coating Preparations & Application
Coatings were prepared using three shape engineered clays, each at two levels with two different binders.
The coating solids and Brookfield viscosities were measured.
Coatings were applied on SBS baseboard using a lab padder (size press) and various Mayer Rod.
The coated samples were then calendered at 1600 PLI, 2-nip smooth side.
All the coated paperboard samples were conditioned for 24 hrs at 50% RH and 230C before any measurements were made.
17
Sample ID for Different Formulations
Pigm
ents
Bin
ders
Pigm
ent
Load
ing
S1 2 A 6%
S4 2 A 100%
S5 1 A 6%
S8 1 A 100%
S9 3 A 6%
S12 3 A 100%
S13 2 B 6%
S16 2 B 100%
S17 1 B 6%
S20 1 B 100%
S21 3 B 6%
S24 3 B 100%
ID
Lab
Padd
er (S
ize
Pres
s)
Pigm
ents
Bin
ders
Form
ula
P1 1
P2 2
P3 3
C1 2 A
C2 1 A
C3 3 A
C4 2 B
C5 1 B
C6 3 B
ID
Dra
wdo
wns
(Rod
Coa
ting
) Pigment Only
100
Parts Pi
gmen
t + 1
0 Pa
rts Bin
der
Pigm
ents
Bin
ders
C1S4 2 A
C2S8 1 A
C3S12 3 A
C4S16 2 B
C5S20 1 B
C6S24 3 B
Size
Pre
ss
+ R
od
ID
18
Testing
The samples were tested for moisture vapor transmission rate (MVTR), PPS porosity, caliper and stiffness (elastic modulus).
MVTR of each test sample was determined by the gravimetric cup method with the coated side towards the humid air
Measurements were carried out at 75% RH and 100°F as well as at 81% RH and 100°F (reported).
Water vapor molecules that permeated the samples were measured and MVTR were calculated.
19
Testing Cont’d The porosity was measured using a PPS tester at
1000 kPa.
Thickness of the samples were measured using a Micrometer.
The permeability coefficient, K was calculated from the PPS porosity and caliper data using the following relationship:
• K (µm2)=0.048838*Q (ml/min)* L (m)
Stiffness was tested using a Taber stiffness tester at 50 and 75% RH and room temperature conditions.
Composite elastic modulus was calculated from the Taber stiffness and caliper data.
20
Results and Discussion
21
Comparison of Barrier and Mechanical Properties of Selected Size Press Coated Samples
ID
PPS Porosity
(ml/min)
PermeabilityCoeff. (µm2)
MVTR (g/m2·d)
Elastic Modulus (GPa)
50% RH & 730F81%RH &1000F
50%RH & 730F
75%RH & 730F
S1 20.6 3.1x10-4 840 6.0 5.6
S4 29.0 4.4x10-4 884 6.3 5.8
S5 28.6 4.2x10-4 913 5.9 5.7
S8 30.2 4.7x10-4 950 5.9 5.8
S9 37.4 6.2x10-4 928 4.9 5.1
S12 32.6 5.1x10-4 958 5.9 5.6
S13 36.3 5.7x10-4 984 5.7 5.5
S16 43.9 7.1x10-4 1052 5.8 4.9
S17 50.7 7.6x10-4 958 7.0 6.7
S20 39.9 6.2x10-4 1038 5.9 6.3
S21 43.3 6.7x10-4 988 6.0 6.2
S24 45.2 7.1x10-4 989 5.7 5.2
22
Comparison of Barrier and Mechanical Properties of Selected Rod & Size Press + Rod Coated Samples
ID
PPS Porosity (ml/min)
Permeability Coeff. (µm2)
MVTR (g/m2*d)
Elastic Modulus (GPa)
50% RH & 730F81%RH &
1000F50%RH &
730F75%RH &
730F
C1 5.63 1.0x10-4 1142 4.5 4.5
C2 6.89 1.2x10-4 1132 4.5 4.4
C3 17.75 3.0x10-4 984 5.0 4.9
C4 6.99 1.2x10-4 1020 5.4 5.3
C5 12.02 2.1x10-4 1079 5.0 4.8
C6 6.23 1.1x10-4 995 5.0 4.9
C1S4 2.32 3.9x10-5 754 4.0 4.0
C2S8 4.94 8.3x10-5 923 5.0 4.9
C3S12 3.44 5.9x10-5 788 5.3 5.3
C4S16 3.14 5.1x10-5 769 5.0 4.9
C5S20 6.66 1.1x10-4 986 6.3 6.0
C6S24 3.34 5.6x10-5 790 5.6 5.6
23
Influence of Application Method [Size Press vs. Rod Coating and Double Coat (SP +Rod)] on Barrier
Properties
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0.0 6.0 12.0 18.0 24.0 30.0 36.0 42.0 48.0
PPS Porosity (ml/ min)
Perm
eabi
lity
Coe
fficient
, K x
104 (µ
m2 )
S4 S8 S12 S16 S20 S24 C1 C2 C3
C4 C5 C6 C1S4 C2S8 C3S12 C4S16 C5S20 C6S24
Size PressRodSP+ Rod
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0.0 6.0 12.0 18.0 24.0 30.0 36.0 42.0 48.0
PPS Porosity (ml/ min)
Perm
eabi
lity
Coe
fficient
, K x
104 (µ
m2 )
S4 S8 S12 S16 S20 S24 C1 C2 C3
C4 C5 C6 C1S4 C2S8 C3S12 C4S16 C5S20 C6S24
Size PressRodSP+ Rod
24
Influence of Binders on Permeability Coefficient of Selected Coatings
(With Kaolin Clay#2, SF- 50-60)
S 16
S 4
C1 C 4 C
4S16
C1S
4
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
A B
Binders
Perm
eabi
lity
Coe
fficient
, K x
104 (µ
m2 )
25
Influence of Application Methods on Permeability Coefficient of Selected Coatings
(Equal Coat Wt.)(With Kaolin Clay#2, SF- 50-60)
C 4
C1
C1S
4
C4S
16
0.00
0.25
0.50
0.75
1.00
1.25
A B
Binders
Perm
eabi
lity
Coe
ffic
ient
,
K x
104 (µ
m2 )
26
Influence of Binders & Application Methods on MVTR of Selected Coatings
(With Kaolin Clay#2, SF- 50-60)S
4 S 16
C 4C
1
C1S
4
C4S
16
0
200
400
600
800
1000
1200
A BBinders
MV
TR (g
/m2 x
d)
C1
C 4
C4S
16
C1S
4
0
200
400
600
800
1000
1200
A BBinders
MV
TR (g
/m2 x
d)
27
Influence of Pigments on Permeability Coefficient of Selected Coatings
[With Binder “A” Acrylic]
S 12
S 8
S 4
C 3
C1 C 2 C
3S12
C2S
8
C1S
4
0.0
1.3
2.6
3.9
5.2
50-60 10-20 80-90
Pigments Shape Factors
Perm
eabi
lity
Coe
ffic
ient
,
K x
104 (µ
m2 )
28
Influence of Pigments on MVTR of Selected Coatings
[With Binder “A” Acrylic]
S 12S 8
S 4 C 3
C1
C 2
C3S
12C2S
8
C1S
4
0
200
400
600
800
1000
1200
50-60 10-20 80-90
Pigments Shape Factors
MV
TR (g
/m2 x
d)
C 2C1
C 3
C1S
4 C2S
8
C3S
12
0
200
400
600
800
1000
1200
50-60 10-20 80-90
Pigments Shape Factors
MV
TR (g
/m2 x
d)
29
Influence of Shape Factor (Coat Wt. ~32 gsm) on Barrier Properties for Pigments Only (No
Binder)
Clay
3
Clay
2
Clay
10.00
1.00
2.00
3.00
50-60 10-20 80-90
Pigments Shape Factors
Perm
eabi
lity
Coe
ffic
ient
,
K x
104 (µ
m2 )
30
Comparison of Elastic Modulus at 50 and 75% RH and 730F of Selected Rod Coated Samples
C6-
50%
RH
C5-
50%
RH
C4-
50%
RH
C3-
50%
RH
C2-
50%
RH
C1-
50%
RH
C 6
-75%
RH
C 5
-75%
RH
C 4
-75%
RH
C 3
-75%
RH
C1-
75%
RH
C 2
-75%
RH
0.0
1.0
2.0
3.0
4.0
5.0
6.0
50-60 10-20 80-90 50-60 10-20 80-90
Pigments Shape Factors
Ela
stic
Mod
ulus
(GPa
)
A B
31
Conclusions
The pigment shape factor appears to have a systematic effect on barrier properties although it is relatively low in some cases.
The medium shape factor pigment (SF ~55) provided the highest barrier properties for the SBS board tested, but the results might be different for boards of different roughness and porosity.
The shape factor significantly impacted the saturation coat weight (where complete coverage occurs).
32
Conclusions Cont’d The double-coated treatment method (size
press/rod) produced the best results for same coat weight.
The effect of application method on barrier properties was found to have a more significant impact on the barrier properties than the SF of the pigment.
As expected, Taber stiffness and elastic modulus decreases with increase in relative humidity. However, there was only a slight impact of pigment shape factor and application method on stiffness.
33
Further Optimization Work
Clay Shape Factor Concentration Dispersion Orientation
Resin Hydrophobic/hydrophilic character Permeability
Coating Preparation Methods Coating Application Methods
Size Press, Rod, Blade, Curtain etc. Multi layers
Finishing Operations
34
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