Processing and Properties of Biaxially Oriented Polypropylene-Based Nanocomposites

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Processing and Properties of Biaxially Oriented Polypropylene-Based

Nanocomposites

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Processing and Properties of Biaxially Oriented

Polypropylene-Based Nanocomposites

September 16th_{, 2008}

Nathalie Chapleau

Structural Polymers and Composites Group

Industrial Materials Institute

National Research Council of Canada

Context and

Objectives

•Several applications for PP-based nanocomposites: • injection molded products

• extruded cast sheets • thermoforming parts • bottles

• blown films, etc.

• Assess the processability of PP-based nanocomposites using a laboratory biaxial stretcher:

• effect of blend formulation on processability and performance • establish structure-process-property relationships

Materials

Matrices

y Polypropylene from Basell

Profax PDC1274 (injection grade) Profax HL451H (extrusion grade, BOPP)

Coupling agents

y Polybond 3150 and S192 from Chemtura y Epolene 3015 from Eastman

Clays

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Blend Content

PPNC1-2 PPNC1-4 % Clois PPNC2-2 PPNC2-4 4 2 4 2 HPPNC1-2 HPPNC1-4 % Clois HPPNC2-2 HPPNC2-4 4 2 4 2

PP matrix

(PDC1274)

HPP matrix

(HL451H)

uncomp. comp.

Blends

(2 and 4 wt.% clay)

PPNC1-2 PPNC2-4 % Clay PPNC1-2 PPNC2-4 4 2 4 2

`

Poor dispersion d = 2.86 nm Good dispersion d = 3.55 nm

Outline

Characterization • rheology • thermal properties • mechanical properties • X-Ray, FTIR Processing • cast extrusion • thermoforming • biaxial stretching • injection molding

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Capillary Rheology

at 200

o

_C

Capillary Rheology

at 200

o

_C

Frequency (rad/s) or Shear rate (s-1)

100 1000 10000 V isco si ty ( P a *s ) 100 1000 HPP HPPNC1-2 HPPNC1-4 HPPNC2-2 HPPNC2-4 PDC1274 HL451H

• higher viscosity for HL451H matrix • adding clay lowers viscosity

• no significant effect of clay on flow properties at high shear rates

Shear Rate (s-1) 100 1000 10000 Shear Vi sc os it y (P a.s ) 10 100 Neat PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4 20 500

Cast Sheet Extrusion

RandCastle Cast film Line

• equipped with flat die • width: 20 cm

• film thickness ~ 1 mm • operating conditions

• melt temperature: 185o_{C for PP, 200}o_{C for HPP} • 100 rpm

• rolls temperature: 30o_C

MD

TD

• tensile properties on rectangular strips (D-882 )

Mechanical Properties

Cast sheets

Mechanical Properties

Cast sheets

E last ic M odulus (G Pa) 1.0 1.5 2.0 2.5 3.0 MD TD PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4 E longat ion at B reak (%) 0 200 400 600 800 1000 1200 MD TD PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4

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Time (ms) 0 1 2 3 4 Load (kN) 0.0 0.2 0.4 0.6 0.8 1.0 1.2

Instrumented Impact

Cast Sheets

(Dynatup)

Instrumented Impact

Cast Sheets

(Dynatup)

PP PPNC2-4

Instrumented Impact

(Dynatup)

Instrumented Impact

(Dynatup)

Neat PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4 Relativ e Total En erg y 0 1 2 3 4 Cast Sheets

E_totalfor neat PP (1 mm) § 2 J

Brückner Laboratory

Biaxial Stretcher

Brückner Laboratory

Biaxial Stretcher

Initial film thickness:

20 to 2000 µm

Min. sample dimension:

85 x 85 mm

Max. draw ratio:

10:1 both axis

Max. draw speed:

0.5 m/s Drawing: sequential or simultaneous Max. force: 2000 N Max. temperature: 250°C

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Brückner Laboratory

Biaxial Stretcher

Brückner Laboratory

Biaxial Stretcher

Drawability results

Maximum biaxial draw ratio Maximum stress

Biaxial Draw ratio

S tress (M P a ) 0 5 10 15 20 1X1 2X2 3X3 4X4 5X5 6X6 MD TD

(cast) Biaxial Draw Ratio

Stress (MPa)

Used to simulate industrial processes

Double-bubble, tenter frame (biaxial orientation), thermoforming, machine direction orientation (MDO)

Biaxial Stretching Ratio

Engineering Stress (MPa)

0 2 4 6 2x2 4x4 6x6 8x8 160°C 165°C MD TD

Biaxial Stress-Strain Curves:

effect of temperature

Biaxial Stress-Strain Curves:

effect of temperature

PP 1274 matrix, initial thickness of 1 mm

Biaxial Stretching Ratio

Engineering Stress (MPa)

0 2 4 6 8 PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4 2 X 2 4 X 4 6 X 6 8 X 8 Cast t§ 40 Pm t§ 15 Pm 160o_C

Biaxial Stress-Strain Curves:

effect of clay and compatibilization

Biaxial Stress-Strain Curves:

effect of clay and compatibilization

• effect of adding clay and compatibilization: increased draw ratio & lower drawing stress

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Mechanical Properties

Biaxial Films

Mechanical Properties

Biaxial Films

Cast Sheets 2 X 2 4 X 4 6 X 6 E last ic M o dulus (GP a) 0 1 2 3 4 5 6 7 PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4

Mechanical Properties

Biaxial Films

Mechanical Properties

Biaxial Films

E longat ion at B reak (%) 0 200 400 600 800 1000 1200 PP PPNC1-2 PPNC1-4 PPNC2-2 PPNC2-4 Cast 2 X 2 4 X 4 6 X 6 HB§ 80% HB§ 30%

Summary

Cast sheets

• addition of clay reduces viscosity

• tensile modulus and strength of nanocomposites higher than or similar to neat PP (values similar in both MD and TD)

• elongation at break drops with clay content; significant differences between MD and TD

• impact resistance of nanocomposite cast sheets higher than neat PP PP-based nanocomposite biaxial films

• Biaxial processability was addressed: • significant effect of temperature

• high biaxial draw ratios can be obtained (increased by addition of clay)

• Tensile properties affected by increasing biaxial draw ratio:

• properties are balanced in MD and TD compared to cast sheets • with addition of clay, modulus increases and strength

decreases slightly

• improved tensile modulus and strength with increasing draw ratio, but lower elongation at break