Formulation and Processing of Polypropylene – Flax Fiber Composites

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Formulation and Processing of Polypropylene – Flax Fiber Composites

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Formulation and Processing of PP- Flax

Fiber Composites

M-T. Ton-That, J. Denault, E. Patenaude and W. Leelapornpisit

Bioplastics 2006

27th_-29th _{September 2006}

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Outline

 Flax structure and properties

 PP composites from flax

Compression

Injection

Extrusion-Injection

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Flax types



Flax

Fibers, Shives, Mix of shives & fibers, Dust (Biolin)

Fiber treatment: non, water, soap and NaOH 1% (50o_{C, 2 h)}

 Polymer matrix

 Injection grade PP Profax 1274 (Basell)

 Coupling agent: maleic anhydride (MA) grafted polypropylenes

 Epolene-43 (Mn = 9,100; ~4.81 wt% of MA) (Eastman Chemical)  Epolene-3015 (Mn = 56,000; ~1.5 wt% of MA) (Eastman Chemical)  Polybond 3150 (Mn = 330,000; ~0.5 wt% of MA) (Chemtura)

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Processing

 Extrusion  Standard TSE, T=190o_{C, 10kg/h, 200rpm}  Injection molding; T=190o_C Wood composite compound Dried blend of fiber, polymer and additives

 Mat fabrication

 Compression molding

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Flax fiber structure

 Single fiber cells and multiple fiber-cell bundles at different

sizes can be observed: very inhomogeneous

 Fiber cell cross-section is not a regular circle

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Flax fiber structure

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Flax fiber structure

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Flax fiber structure

 Weak bonding between the fiber cells in the bundle

 Many deffects inside the fiber cell cross-section

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Flax fiber structure

 Hollow and porous

structure can also be

observed

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Flax fiber structure

 Hollow and porous structure

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Flax fiber structure

 Splitting of elementary fiber

and the meso structure in

the secondary cell wall

 Fiber with intercellular

bonding

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Flax fiber properties

 Tensile strength: 280  120 MPa

expected: 780 MPa

 Tensile modulus: 15.8  1.5 GPa

expected: 27.5 GPa

 Diameter: 10-120

μm

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Mechanical properties

Compression molding

 Modulus and strength of the composites improve significantly with the presence of coupling agent

 Type of coupling agent also plays an important role

 The presence of CaO provide a great increase in modulus

25 30 35 40 45 PP 30% FLA X 30% FLA X+P B31 50 30% FLA X+E P30 15 30% FLA X+E 43 30% FLA X+E 43+C aO Te ns il e s tre ng th (M P a ) 1000 2500 4000 5500 7000 Te ns il e m od ul us ( M P a ) Strength Modulus

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Interface

No coupling agent

 Very poor interaction between the fiber and the matrix

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Interface

With coupling agent

 Great improvement at

the interface

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Interface

With coupling agent and CaO

 Good interface

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Mechanical properties

–

Injection molding

 Properties equivalent to wood-PP composites  Process not optimized

 Grinding  Extrusion  Injection 20.00 25.00 30.00 35.00 40.00 PP 30% FLAX +E43 +CaO T e n s il e s tr e n g th ( M P a ) 1000 2000 3000 4000 5000 T e n s il e m o d u lu s ( M P a ) Strength Modulus 50.00 55.00 60.00 65.00 PP 30% FLAX +E43 +CaO F le x u ra l s tr e n g th ( M P a ) 1000 2000 3000 4000 F le x u ra l m o d u lu s ( M P a ) Strength Modulus 6.00 9.00 12.00 15.00 18.00 PP 30% FLAX +E43 +CaO Iz o d i m p a c t s tr e n g th ( k J /m 2 )

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Various Flax types

Extrusion-injection

Effect of fiber type (40% )

30 33 36 39 42 45

Shive Fiber Mix Dust

T e n s il e s tr e n g th ( M P a ) 3000 3500 4000 4500 5000 T e n s il e m o d u lu s ( M P a ) Strength Modulus

 All types of flax, even dust, provide a significant imporvement in strength and modulus (neat PP: 25MPa and 1400MPa, respectively)  very positive!

 The longer the reinforcement length, the greater the tensile strength and

impact strength as the result of high aspect ratio (although fiber length has been reduced significantly during extrusion and injection)

Effect of fiber type (40%)

22 26 30 34

Shive Fiber Mix Dust

N o tc h e d I zo d i m p a c t s tr e n g th ( J /m )

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Flax shive PP composites

Extrusion-injection

 The presence of shives increases significantly the tensile strength (>35%) and modulus (180-300%) without affecting the impact strength

 The increase of shive content in the composites also increases linearly the tensile modulus but not the tensile strength

Effect of shive content

22 26 30 34

0% shive 30% shive 40% shive 50% shive

Effect of shive content

20 23 26 29 32 35 38

0% shive 30% shive 40% shive 50% shive

T e n s il e s tr e n g th ( M P a ) 1200 2000 2800 3600 4400 5200 6000 T e n s il e m o d u lu s ( M P a ) Strength Modulus

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Mix shives-fibers

Extrusion-injection

 The presence of mixture of shives and fibers increases significantly the tensile strength (>35%), tensile modulus (160-300%) and the impact strength (~12%)  The increase of the content of mixture of shives and fibers in the composites also increases linearly the tensile modulus and the tensile strength

Effect of mix fiber-shive content

20 23 26 29 32 35 38

0% mix 30% mix 40% mix 50% mix

T e n s il e s tr e n g th ( M P a ) 1200 2000 2800 3600 4400 5200 6000 T e n s il e m o d u lu s ( M P a ) Strength Modulus

Effect of mix fiber-shive content

22 26 30 34

0% mix 30% mix 40% mix 50% mix

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 CaO improves more than 15% tensile modulus without sacrifying the

tensile strength

 Impact strength was not affected by CaO (as standard deviation is

taken into account) and remains the same as pure PP (25 J/m)

Effect of CaO 30 32 34 36 38 40 40%Shive-0%CaO 40%Shive-10%CaO 40%Mix-0%CaO 40%Mix-10%CaO T e n s il e s tr e n g th ( M P a ) 3000 3400 3800 4200 4600 5000 T e n s il e m o d u lu s ( M P a ) Strength Modulus

Effect of CaO

Extrusion-injection

Effect of CaO 22 26 30 34 40%Shive-0%CaO 40%Shive-10%CaO 40%Mix-0%CaO 40%Mix-10%CaO N o tc h e d I zo d i m p a c t s tr e n g th ( J /m )

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Roles of CaO

 CaO

 Absorbs humidity in flax

 Neutralizes acidity in flax

 minimize degradation during processing

 Reacts with maleic anhydride group of coupling agent

Improve interface between flax and PP matrix Increase molecular weight of coupling agent Limit a loss in toughness and impact

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Interaction between CaO and

coupling agent - FTIR study

 Evidence of chemical reaction between coupling agent and CaO

0.0 0.5 1.0 1500 1600 1700 1800 1900 2000 Ab so rb a n ce Wavenumber PP ref. PP-E43 PP-E43-CaO (1) PP-E43-CaO (2) PP-CaO Anhydride Acid (dimer) -COOH Ca carboxylate -COO -Spectra as measured

(thin hot-pressed films in transmission)

Difference spectra obtained by subtracting PP ref. 0.0 0.5 1.0 1500 1600 1700 1800 1900 2000 Ab so rb a n ce Wavenumber PP-E43 PP-E43-CaO (1) PP-E43-CaO (2) PP-CaO Anhydride Acid (dimer) -COOH Ca carboxylate -COO -Carbonate CO 3

2-COOH _CaO _COO _COO

+

Ca

Coupling agent

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Dispersion and Interface

Fiber composites

 Good dispersion and

distribution of shives

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Dispersion and Interface

Mixed fiber-shive composites

 Very good

dispersion of

shives and

fibers in the

matrix and

great

reduction of

fiber length

can be

observed

 Crystalline

structure of

PP matrix

remains

 Very good

fiber-matrix

interface

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PLA-Flax Composites

Effect of PLA type

50 54 58 62 66 70 PLA-a PLA-a-40%Mix fiber-shive PLA-c PLA-c-40%Mix fiber-shive T e n s il e s tr e n g th ( M P a ) 3000 3800 4600 5400 6200 7000 7800 T e n s il e m o d u lu s ( M P a ) Strength Modulus

Effect of PLA type

22 26 30 34 PLA-a PLA-a-40%Mix fiber-shive PLA-c PLA-c-40%Mix fiber-shive N o tc h e d I zo d i m p a c t s tr e n g th ( J /m )