Preparation of Polyethylene/Montmorillonite (MMT)Preparation of Polyethylene/Montmorillonite (MMT) Nanocomposites Through in situ Polymerization Using a Montmorillonite Supported Nickel Diimine Catalysta Montmorillonite-Supported Nickel Diimine Catalyst

Yiyoung Choi, Sang Young A. Shin, João B.P. Soares

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1. Introduction

Properties & Applications of Polyolefin/Layered Silicate Nanocomposites

Polymer/layered silicate nanocomposites provide the better performance characteristics when compared to virgin polymer or conventional composites.

Recently, the success on polymer/layered silicate nanocomposites has extended into making high performance pol olefin nanocompositespolyolefin nanocomposites.

Application Polyolefin/Layered Silicate Nanocomposites have

Improved Mechanical strength Auto parts

Improved Thermal Stability

Cf.) Tortuous paths Improved Gas-barrier Properties

Film

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1. Introduction

Structure of Layered Silicates- Montmorillonite

Montmorillonite (MMT) has been used as the main material for polymer/layered silicate nanocomposite Montmorillonite (MMT) has been used as the main material for polymer/layered silicate nanocomposite due to its remarkable intercalation ability. MMT is consisted of stacks of each silica/alumina phase and gallery.For preparation of polymer/MMT nanocomposite, single layer of MMT is exfoliated and dispersed into polymer matrix.To make it easy dispersion, hydrophilic MMT are converted to the ones with organophilic surface.

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1. Introduction

Several Techniques for Polymer/Layered Silicate Nanocomposites

Technique ofPLS Preparationp

Method 1 Method 2 Method 3

In-situ Polymerization Melt Compounding Solution Blending

Polyolefin/Layered Silicates (MMT) Nanocompositeso yo e / aye ed S ca es ( ) a oco pos esMethod 1. Easier intercalation of monomer but it needs understanding of polymerization catalyst and process.Method 2. Simple but organic modifier of MMT is decomposed by harsh condition, it leads agglomerization of MMT. Method 3. Impossible method due to poor solubility of polyolefin.

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1.Introduction

Polyethylene/MMT Nanocomposites Using In-situ Polymerization

1) 3 types of montmorillonite (MMT) were used, and modified with trimethyl aluminum. 2) Nickel diimine catalyst was intercalated in the MMT galleries.) y g3) Formation of polyethylene inside the galleries leads to the exfoliation of the MMT.

Exfoliation of MMT by Ethylene polymerization

CatalystCatalyst

MMT Intercalation of Catalyst

Catalyst

G i l h iCatalyst

Growing polymer chain

CC

OH

CHN HT

(1)Cloisite Na (2)Cloisite 30B (3)Cloisite 93AUsed MMTs

5

T N C

CC OH

C N HT

HT

T, tallow (~65% C18, ~30% C16, ~5% C14)

Na

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2. Experimental

Materials

All operations were performed under nitrogen (99.999%, Praxair) using standard Schlenk techniques or inside Glove-box.

General Solvents (Toluene, Hexane, Methylene dichloride, etc )Purchased from VWR and purified with activated alumina and 3A/4A mixed molecular sieves.

Synthesis of Nickel Diimine Catalyst Purchased from Aldrich or Acros and used without purification

MMTs (Cloisite Na Cloisite 30B and Cloisite 93A) for Catalysts Supporting MMTs (Cloisite Na, Cloisite 30B and Cloisite 93A) for Catalysts Supporting Purchased from Southern Clay Products and used after drying under vacuum at 60oC overnight.

In situ polymerization Ethylene (99.9%, Praxair) was purified with R3-11 copper catalyst, activated alumina and 3A/4A mixed molecular sieves

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2. Experimental

Nanocomposite Characterization

Differential Scanning Calorimetry (DSC, Q2000, TA Instruments)Thermal Gravimetric Analysis (TGA, Q500, TA Instruments) X-ray Diffractometer (XRD, D8-Focus, Bruker)Scanning Electron microscope (SEM, LEO 1530 FE-SEM) Transition Electron microscope (TEM, CM12, Philips)

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3. Results and Discussion

Synthesis of Nickel Diimine Catalyst with Functional Group

O O

N NNH2Toluene

H2SO4H2N H2N NH22

CH ClNiBr2(DME)

CH2Cl2N NH2N NH2 N NH2N NH2

NiBr Br

bis(4-amino-2,3,5,6-tetramethylimino)acenaphtene nickel(II) dibromide

P. P. Pflugl, M. Brookhart, Macromolecules 2002, 35, 6074

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3. Results and Discussion

Synthesis of MMT-Supported Nickel Diimine Catalyst -1) C30B

1) Cloisite 30B was reacted with TMA for the organic modification and reactive groups generation. 2) Amine functionalized nickel diimine catalysts were supported onto Cloisite 30B gallery through chemical bonding.

C CTMA Nickel Diimine CatalystT N C

C

C C OH

C OH CatalystT N C

C

C C O

C O Al

Al Catalyst

TGA analysis XRD patterns

MMT (Cloisite 30B) Cloisite 30B-Supported Nickel Diimine Catalyst (C30B)

ity260oC 390

oC

4.9o (18.0 A)

Rel

ativ

e In

tens

i

Cloisite 30B

C30B

360oC 4.1o (21.6 A)7.6o (11.6 A)

92 3 4 5 6 7 8 9 102 Theta

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3. Results and Discussion

Synthesis of MMT-Supported Nickel Diimine Catalyst- 2) C93A

1) Nickel diimine catalyst was physisorbed onto Cloisite 93A surface or gallery.

Catalyst

TMA Nickel Diimine ComplexCatalyst

C

NH

TH

TH

C

NH

TH

THCatalyst

TGA analysis XRD patterns

MMT (Cloisite 93A) Cloisite 93A-Supported Nickel Diimine Catalyst (C93A)

TH

360oC400oC

y XRD patternsty

C93A

Rel

ativ

e In

tens

i

Cloisite 93A

102 3 4 5 6 7 8 9 10

C93A

2 Theta

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3. Results and Discussion

Synthesis of MMT-Supported Nickel Diimine Catalyst- 3) CNa

TMA Nickel Diimine CatalystCatalyst

1) Nickel diimine catalyst could be physisorbed onto Cloisite Na surface or gallery.

y

MMT (Cloisite Na)MMT-Supported Nickel Diimine Catalyst (CNa)

CatalystNa Na

TGA analysis XRD patterns

tens

ity

Cloisite Na

CNa

Rel

ativ

e In

11

2 3 4 5 6 7 8 9 102 Theta

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3. Results and Discussion

In Situ Polymerization

1) MMT layers are exfoliated by growth of polyethylene, and it means nano size layers are distributed into polyethylene matrix.

Catalyst

Catalyst

Catalyst

Ethylene Polymerizatoin

CatalystCatalystCatalyst

Intercalation of Catalyst

Exfoliated MMT into PE matrix

(Slurry batch reactor Hexane solvent Continuously ethylene feeding EASC activator or no activator)

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(Slurry batch reactor, Hexane solvent, Continuously ethylene feeding, EASC activator or no activator)

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3. Results and Discussion

In Situ Polymerization Results - 1) Catalyst Activity Profiles

1) MMT supported catalysts systems show very stable activity profile. 2) A series of PE/MMT nanocomposites with different MMT fractions were prepared by varying the polymerization time.

C t l t A ti it P fil (C30B U t d C t l t)

200 - Condition: 60 oC, Ethylene 50 psi, no activator

C30B

Catalyst Activity Profiles (C30B vs. Unsupported Catalyst)

150

w [m

l/min

]

- C30B- Unsupported Catalyst

100

thyl

ene

Flow

MMT 14.3%MMT 8 3% MMT 3 8%

0

50E MMT 8.3% MMT 3.8%

13

0 50 100 150 200

Time (min)

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3. Results and Discussion

In Situ Polymerization Results- 1) Catalyst Activity

1) C30B shows the highest yield.2) C30B comparable catalyst activity in the absence of EASC activator, but CNa and C93A had not catalyst

activity without EASC activator.

Catalyst Activity OAl

Structure of C30B

EASC activator

No activator Al

N NH2N NHNi

C

O

TN

OAl

T NC

Al

C

O

C

Aluminoxane linkage could function as activator for C30B

C

14- Condition: 60 oC, Ethylene 50 psi,

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3. Results and Discussion

In Situ Polymerization Results- 2) Crystallinity & Melting Temperature of Nanocomposites

C30B without activator made nanocomposite with the highest Tm and crystallinity.

Crystallinity Melting TemperatureCatalyst

High steric hindrance causes fewer short

Catalyst

Catalyst

chain branched PELow steric hindrance causes higher short chain branched PE

15- Polymerization Conditions: 60 oC, Ethylene 20 psi, EASC activator or no activator

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3. Results and Discussion

In Situ Polymerization Results- 3) Decomposition Temperature of PE/C30B

Td of nanocomposites with C30B were similar with reference homogeneous PE resin (473.4 oC).Good dispersion of the MMT layers in the polymer matrix, resulting in enhanced thermal stability of the nanocomposites nanocomposites.

2.5 473.6 oCPE/C30B

1 5

2.0

ght (

%)

PE(83)/C30B(17) nanocomposite PE(93)/C30B(7)composite

1.0

1.5

eriv

ativ

e W

eig

200 250 300 350 400 450 500

0.0

0.5De

16- Polymerization Conditions: 60 oC, Ethylene 50 psi, no activator

200 250 300 350 400 450 500

Temperature (oC)

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3. Results and Discussion

In Situ Polymerization Results- 3) Decomposition Temperature of PE/C93A and CNa

1) Td of nanocomposites using CNa and C93A were lower than that of the reference homogeneous PE resin (473.4 oC)2) As MMT contents increase, Td of nanocomposites decreases. 3) MMT and/or alkyl modifier accelerate the degradation of PE.3) MMT and/or alkyl modifier accelerate the degradation of PE.

2.52 5

PE/CNa PE/C93A

1 5

2.0

ght (

%)

PE(87)/CNa(13) nanoomposite PE(95)/CNa (5) nanocomposite

2.0

2.5

ht (%

)

PE(88)/C93A(12) nanocomposite PE(95)/C93A(5) nanocomposite

1.0

1.5

Der

ivat

ive

Wei

g

1.0

1.5

eriv

ativ

e W

eig

200 250 300 350 400 450 500

0.0

0.5D

200 250 300 350 400 450 500

0.0

0.5De

17- Polymerization Conditions: 60 oC, Ethylene 50 psi, EASC activator

200 250 300 350 400 450 500

Temperature (oC) Temperature (oC)

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3. Results and Discussion

In Situ Polymerization Results- 4) XRD Patterns of PE/C30B

As increased polymerization time (lower C30B contents), the MMT layers were exfoliated.

PE(77)/C30B(23) nanocomposite 15 2 A

PE/C30B

PE(93)/C30B(7) nanocompositeten

sity

15.2 A

PE(93)/C30B(7) nanocomposite

Rel

ativ

e In15.0 A

2 3 4 5 6 7 8 9 102 Theta

18- Polymerization Conditions: 60 oC, Ethylene 20 psi, EASC activator

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3. Results and Discussion

In Situ Polymerization Results- 4) XRD Patterns of PE/CNa and C93A

As increased polymerization time (lower MMT content), the MMT layers were not fully exfoliated.

PE/CNa PE/C93A

nsity

PE(87)/CNa(13) nanocomposite 19.6 A

nsity

PE(94)/CNa(6) nanocomposite

Rel

ativ

e In

te

15.0 APE(87)/C93A(13) nanocomposite

Rel

ativ

e In

te

PE(94)/C93A(6) nanocomposite

2 3 4 5 6 7 8 9 102 Theta

2 3 4 5 6 7 8 9 102 Theta

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- Polymerization Conditions: 60 oC, Ethylene 20 psi, EASC activator

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3. Results and Discussion

In Situ Polymerization Results- 5) SEM Micrographs of Supported Catalyst

C30B shows irregular particles in the 2-3 μm width. The edge of the C30B particles are “curly”, indicating that MMT layers have been intercalated and exfoliated by diffusion of the reactants from their edges to their centers during supporting process.

C30B1 μm 0.3 μm

C30B

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3. Results and Discussion

In Situ Polymerization Results - 5) SEM Micrographs of Nanocomposites

Free-flowing nanocomposite particles were obtained without reactor fouling.The MMT layers appear as stacks connected by polymer strips and fibrils of different lengths and width. y pp y p y p g

200 μm 0 3 PE/C30B

0 5 μm200 μm 0.3 μm0.5 μm

TEM

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3. Results and Discussion

In Situ Polymerization Results- 5) TEM Micrographs of Nanocomposites

1. The MMT layers are oriented in planes that are parallel to the slicing plane, appearing as dark regions.

2. The MMT layers are oriented perpendicularly to the slicing plane, showing very good

200 nm

13 2. The MMT layers are oriented perpendicularly to the slicing plane, showing very good

exfoliation.3. Several layers of MMT appear to be completely exfoliated and seem to “flow” with the

polymer.2

3

p y

50 nm1 2 3

50 nm 50 nm

2

50 nm 50 nm 50 nm

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- Particle Fragmentation Mechanism 1. Large MMT particles are broken into several smaller particles.2

3. Results and Discussion

2. The MMT layers are exfoliated by growing polymer. 3. Nanophase distribution of MMT layers on the polymer matrix.

Step 1

Step 2

St 3Step 3

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C l i

4.

Conclusion

1. PE/MMT nanocomposites were prepared by in situ polymerization with a functionalized nickel diimine catalyst on Cloisite Na and two organically modified MMTs, Cloisite 93A and Cloisite 30B.

2. The particle intercalation and exfoliation was initiated by the insertion of the nickel diimine catalyst into TMA-modified MMT galleries, and continued even further during the polymerization by the formation of polymer chains within the clay galleries. p y y g

3. C30B made nanocomposites with better thermal properties than those made with CNa and C93A. 4. C30B was active for ethylene polymerization even in the absence of the EASC activator. 5 SEM d TEM i h fi d th f ti f h f MMT l di t ib t d i th 5. SEM and TEM micrographs confirmed the formation of a nanophase of MMT layers distributed in the

polymer matrix. Yiyoung Choi, Sang Young A. Shin, João B.P. Soares, Macromol. Chem. Phys. 2010, 211,1026

Thank you!24

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