2006 International Conference on Nanotechnology, April 26 ... · 1. Saponite clay and...

2006 International Conference on

Nanotechnology, April 26-28, 2006

Atlanta, GA

Polymer/Clay Nanocomposites for

Paper Barrier CoatingPresented by: Qunhui Sun and Yulin DengSchool of Chemical and Biomolecular EngineeringIPST @ GT, Georgia Institute of Technology

Polymer/clay Nanocomposites for Paper Barrier Coating

Background of Paper Barrier Coating

Meat preservation, milk, juice, ice cream, meet,fish, fruit, microwave fast food, food plates andboxes, drink cups, photo papers, etc

Coating Materials

• Organic and polymeric coating layer, such as wax, PE (Polyethylene), PTFE (Polytetrafluoroethylene), PP (polypropylene), PET (Polyethylene teraphthalate), etc

• Metal layers, such as Al, Cu, etc• Ceramic and metal oxide films


Coating Approaches

• Extrusion

• Coextrusion Coating: extruding several layers of polymers onto a substrate

• Impregnation coating

• Vacuum deposition



Some most common problems• Primer layers are generally required for an effective coating

• Unrepulpability of the recycling paper or board

• Other problems of waxed food containers: limited to low temperature applications


Advantages of waterborne nanocomposites for barrier coating

• Environmental friendly

• Cost effective

• Nanocomposites should provide high barriers

Gravure print Coating

Impregnation Coating

Cationic SurfactantAdditivesAdditives

PolymerPolymer

CationCation exchange byexchange by

IntercalationIntercalation

delaminating delaminating with polymerwith polymer

Exfoliation Exfoliation Additives intercalationAdditives intercalation

ExfoliationExfoliation

Mechanical shearing resulting Mechanical shearing resulting in fully exfoliationin fully exfoliation



Our two approaches to make water-based nanocompositesuspension

1. In-situ emulsion or miniemulsionpolymerization

2. Mechanical blending

UnexfoliatedClay particles

Unexfoliated Saponite Exfoliated Saponite

Challenges:1. Nanoclay must be well dispersed in water-latex solution: hydrophilic surface

is preferred 2. Nanoclay must have high affinity with polymer matrix after drying:

hydrophobic surface is preferredKey question:Could bentonite and saponite clays be exfoliated by a simple mixing technique?

Why does the particle have to be a nanosized?


The thickness of nanoclay in the composite is about 1nm.

One bentonite particle can split in to 30-40 layers

If 3% of nanoclay is needed, which equals 90% (= 3%x30) of large clay to keep the same total surface area.

Raw Materials and method

Polymers used: Two acrylics suspensions (763A, 763B) and a styrene-butadiene copolymer latex (226-NA) (commercially available barrier coating polymers from two different chemical suppliers)

Clays used: 30B (Cationic exchanged Cloisite 30B, Southern Clay)

H1 [cationic polymer and polystyrene modified KSF (a montmorrilonite from Southern Clay)]

Sap-CTAB (Saponite modified with cationic surfactant, Sumecton SA, kunimine industries Co., Ltd. Japan)

Modification methods: Cation exchange; in-situ solution polymerization.


PCNC (polymer-clay nanocomposite) preparation procedures

Formulation: Aqueous solution mixing;

Mechanical treatment: Ultrasonification and stirring;

Coating method: Hand roller coating;

Drying: Infrared light drying


PCNC preparation procedureSurface treatment ofclay via cationexchange

Mixing with suspensionpolymer latex and additives

Ultrasonification

Pristine clays

Homogeneous PCNC


Characterization and test methods:

Cobb test: TAPPI T441 om-98;

WVTR (water vapor transmission rate): TAPPI T448 om-97;

XRD: PW 1800 X-ray diffractometer;

DSC, TEM


Table 1 Stability of 30B and H-1 in Aqueous Systems*

Swollen at bottomH-1 + TW85 + PAA + 763A + Water-10

HomogeneousH-1 + TW85 + PAA + Water+9

Yellow, swollen, and delaminatedH-1 + TW85 + Water-8

Yellow, swollen, and delaminatedH-1 + PAA + Water--7

Yellow, precipitated out at bottomH-1 + Water---6

Milky, homogeneous30B + TW85 + PAA + 763A + Water++5

Milky, homogeneous30B + TW85 + PAA + Water ++4

Milky, homogeneous30B + TW85 + Water+3

Milky, swollen , and phase separated30B + PAA + Water--2

Milky, swollen, and phase separated30B + Water--1

NotesCompositionStability1No.

•The clay loading was 30 wt.% of solid polymers.•TW85: surfactant Tween-85; PAA: polyacrylic acid sodium salt1 --, very poor; -: poor; +: good; ++: very good.


A B C D E

Stability observation of 30B aqueous systems. A: 30B+water; B: 30B+PAA+water; C: 30B+TW85+Water; D: 30B+TW85+PAA+Water; and E:30B+TW85+PAA+763A+Water. The preparation method was the same asdescribed above. The clay loading was 30 wt.% of solid polymers.


A B C D E

Stability observation of H-1 aqueous systems. A: H-1+water; B: H-1+PAA+water; C: H-1+TW85+Water; D: H-1+TW85+PAA+Water; and E: H-1+TW85+PAA+763A+Water. The preparation method was the same as described above. The clay loading was 30 wt.% of solid polymers.


0

20

40

60

80

100

30BSap-CTABH-1763-A

Cobb

Val

ue (g

m-2 0

.5 h

-1)

Clay Varieties

Water resistance (Cobb test) of barrier coatings comprised of 763A and 763B with various clays. The clay loading was 10 wt.% of solid polymer.

0

20

40

60

80

100

30BSap-CTABH-1763-B

Cob

b Va

lue

(g m

-2 0

.5 h

-1)

Clay Varieties


0

60

120

180

240

300

30BSap-CTABH-1763-A

WVT

R (g

m-2 2

4 h-1

)

Clay Varieties

Water vapor resistance (WVTR) of barrier coatings comprised of 763A and 763Bimpregnating with various clays. The clay loading was 10 wt.% of solid polymer.

0

60

120

180

240

300

30BSap-CTABH-1763-B

WVT

R (g

m-2 2

4 h-1

)Clay Varieties


0

20

40

60

80

100

120

763-A226-NA763-B

Cob

b Va

lues

(g m

-2 0

.5 h

-1)

Polym er Matrixes

The blank columns indicate the Cobb values of the pure polymer matrix, while the dense parts refer to the Cobb values of the composite systems. The preparation procedures were the same as described above.


Influence of different polymer matrixes on water resistance (10% nanoclay 30B was used).

0 5 10 15 20 25 30

20

40

60

80

100

120

in 226NA

in 763-A

in 763-B

Clay content (wt. part to polymer)

Cob

b Va

lues

(g/m

2 30

m)

Influence of 30B content on the water resistance of PCNCs. The recipes are as the follows: Polymer latex solution or suspension dispersion: 10 g; D.I. water: 10g; clay: 3-30 wt.% of solid polymer; TW-85: 10 wt.% of clay; PAA: 50 wt.% of TW-85. The mixing conditions were the same as described above.

Polymer/Clay Nanocomposites for Paper Barrier Coating

20

40

60

80

100

120

140

0 3 6 9 12 15

80

100

120

140

160

180

200

220

240

WVT

R (g

/m2 2

4 h)

Cobb

Val

ue (g

/m2 0

.5 h

)

Cobb

Sap-CTAB Content (wt.%)

WVTR

Relationship between Cobb and WVTR values and modified Sap-CTAB contentin the polymer matrix of 763-A. The recipes are as the follows: 763A dispersion: 10 g; D.I. water: 10g; clay: 2-16 wt.% of solid polymer; TW-85: 10 wt.% of clay; PAA: 50 wt.% of TW-85. The mixing conditions were the same as described above.


0 3 6 9 12

F

E

D

C

B

A

2 θ (o)

A: pristine Saponite; B: Sap-HCl; C: Sap-CTAB; D: PCNC-763A (Sap-CTAB); E: PCNC-763B (Sap-CTAB); F: Sap-CTAB +TW85+PAA +763A+Water


XRD patterns change of Saponite clay in the composites

0 2 4 6 8

5

4

3

21

B

A

2 θ ( o )

1: pristine 30B; 2: 30B+Water; 3: 30B+TW-85+Water;4: 30B+TW-85+PAA+Water; and 5: 30B +TW85+PAA +763A+Water


XRD patterns change of nanoclay 30B in the composites

0 1 2 3

F

E

D

C

B

A

2 θ (o)

A: pristine H-1; B: H-1+Water; C: H-1+TW-85+Water; D: H-1+PAA+Water; E: H-1+TW-85+PAA+Water; and F: H-1+TW85+PAA +763A+Water


XRD patterns change of nanoclay H-1 in the composites

1 1 0 1 2 0 1 3 0 1 4 0

< en

doth

erm

ol (a

.u.)

C

B

A

130 .5

126 .2130 .4

133 .6

123 .7127 .4

T em p erature (oC )

DSC diagrams of polymer/modified montmorrilonite clay nanocomposites. A: pristine polymer latex 763A; B: 763A-H1-Water; and C: 763A-H1-TW85-PAA-Water.


Conclusions

1. Saponite clay and montmorrilonite clay nanocomposite could be prepared via an aqueous solution mixing approach;

2. The nanoclays could be fully exfoliated in the polymer matrix by a simple aqueous solution mixing process under ultrasonification

3. The agglomerates or macroparticles formation by clay particles in the polymer matrix result in pinholes or defects formation in the coating layer.

4. A simple economic estimation revealed that although the nanoclays are more expensive than the polymer latex, the overall costs of the PCNCsprepared are ca. 13 % lower than the pure polymer latex system, in terms of a thinner layer formation and ca. 300 % performance improvement at 10 wt.% nanoclay addition.


Acknowledgment

NSF (CTS-0350561), IPST financial support

Dr. R. Popil; Mr. J. Cagle; Mrs. Y. Berta; Dr. M. Bucknan; Mr. Z. Zhou, Ms.Z. Tong; Ms. K. Nelson

Thank You


2006 International Conference on Nanotechnology, April 26 ... · 1. Saponite clay and...

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