Impact Modification of PLA Using Biobased, Biodegradable MirelTM PHB Copolymers Raj Krishnaswamy, Allen Padwa* Metabolix, Inc. *Speaker

© 2013 Metabolix 2

OUTLINE

Background on PLA, PHB Copolymers

PLA Impact Modification Approaches

Results on PLA/PHB Copolymer Blends

Summary

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Poly(lactic acid)

Biobased and compostable aliphatic polyester

NatureWorks, LLC has demonstrated success in a variety of sheet, fiber and blend applications

Low impact toughness and low end-use temperature are important considerations for even larger-scale commercial adoption of PLA

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PLA Toughening Approaches (1 of 8)

Plasticizers Mineral Fillers Traditional Impact Modifiers Other Compostable Polymers

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PLA Toughening Approaches (2 of 8)

Plasticizers –Citrate esters & low-Mw PEG have shown

only modest improvements in toughness –Tensile strength is lowered –Tg is reduced (depending on miscibility). Lowering Tg accelerates physical aging at room temperature, which results in shelf-life concerns.

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PLA Toughening Approaches (3 of 8)

Mineral Fillers –Precipitated CaCO3 (EM Force Bio), at 30% loading, provides substantial improvement in the impact toughness of PLA.

Pure

PLA

PLA/

CaCO

3 70

/30

Izod

Impa

ct (f

t.lb/

inch

.)

0.0

0.5

1.0

1.5

2.0

2.5

Pure PLA

30%

EM

For

ce B

io C

aCO

3

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PLA Toughening Approaches (4 of 8)

Traditional Impact Modifiers –Ethylene acrylate copolymers [Biomax

Strong 120] –TPU modifiers [Estane 2102] –ABS modifiers [Blendex 3160; 60% rubber]

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PLA Toughening Approaches (5 of 8)

Traditional Impact Modifiers @ 10% Loading; Compounded by twin-screw extrusion.

Pure

PLA

Biom

ax S

trong

120

Esta

ne 2

102

Blen

dex

3160

Izod

Impa

ct (f

t.lb/

inch

.)

0

2

4

6

8

10

12

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PLA Toughening Approaches (6 of 8)

Traditional Impact Modifiers –ABS impact modifiers [Blendex 3160; 60%

rubber] provide significant impact toughening of PLA.

–However, adding any of these impact modifiers will compromise the compostability of the PLA. Biobased carbon content is also lowered.

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PLA Toughening Approaches (7 of 8)

Other Compostable Polymers –PCL has shown modest promise. –PBS, PBSA, and PBAT are also

promising.

Amongst all compostable polymers, PBSA has shown the best impact modification of PLA. –US Patent 5,883,199 [McCarthy, et. al.]

will serve as a benchmark in our effort

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PLA Toughening Approaches (8 of 8)

PLA/PBSA BlendsUS Patent 5,883,199

Wt% PBSA0 10 20 30 40 50 60 70

Tens

ile E

long

atio

n (%

)

0

100

200

300

400

500

PLA/PBSA BlendsUS Patent 5,883,199

Wt% PBSA0 10 20 30 40 50 60 70Te

nsile

Tou

ghne

ss (M

J/m

3 )

0

20

40

60

80

100

120

140

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Objective

Impact Modification of PLA Using PHB Copolymers –Without compromising biobased

carbon content AND compostability of PLA

–Will explore semi-crystalline PHB copolymer (sc-PHB) amorphous, low Tg PHB copolymer (a-PHB)

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MirelTM PHB Copolymers

Biobased Sugar used as feedstock

Fermentation Microbial engineering enables high polymer accumulation in microbes as well as control of polymer structure

Products Can be fabricated using conventional plastics processing equipment.

Biodegradable • Soil (Ambient) • Home Compost • Industrial Compost • Fresh Water • Marine Water •Anaerobic

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sc-PHB Copolymers

Poly(3-hydroxy butyrate) homopolymer – Highly crystalline (~ 65%), high Tm (~ 160C)

With copolymers, control of Tg, Tm and crystallinity is possible.

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DSC of sc-PHB Copolymer

About 20% crystalline Low Tg phase

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PLA/sc-PHB Blends

Wt% M41000 5 10 15 20 25 30 35

Elon

gatio

n to

Bre

ak (%

)

0

50

100

150

200

250

300Regular BlendsCompatibilized Blends

Wt % sc-PHB

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PLA/sc-PHB Blends

Wt% M41000 5 10 15 20 25 30 35

Tens

ile T

ough

ness

(J)

0.0

0.4

0.8

1.2

1.6

2.0 Regular BlendsCompatibilized BlendsPBSA Blend (USP 5,883,199)

impr

ovem

ent

over

ben

chm

ark

Wt % sc-PHB

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Blends with other Compostable Polymers

Pure

PLA

PBAT PBS

M41

00

Izod

Impa

ct (f

t.lb/

inch

.)

0.2

0.4

0.6

0.8

1.0

1.2

sc-PHB impact modification is similar to that of PBS & PBAT.

10% loading of second polymer into PLA

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DSC of a-PHB

a-PHB is an amorphous, low-Tg rubber.

Cool at 10C/min

Heat at 40C/min

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Wt% M43000 10 20 30 40 50

Izod

Impa

ct (f

t.lb.

/inch

)

0

2

4

6

8

10

12Standard BlendsCompatibilized Blends

PLA/a-PHB Blends

• Significantly improved over sc-PHB

• Compatibilized blends much better.

Wt % sc-PHB

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PLA/a-PHB Blends

Wt% M43000 10 20 30

Tens

ile S

tren

gth

(MP

a)

35

40

45

50

55

60

65

70

75 Standard Blends Compatibilized Blends

Tensile strength is higher for compatibilized blends. Trend similar to other compostable polymers such as PBS & PBAT.

Wt % sc-PHB

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PLA/a-PHB Blends

Wt% M43000 10 20 30

Tens

ile M

odul

us (M

Pa)

1000

1500

2000

2500

3000 Tensile modulus is not as greatly influenced by compatibilization. Trend similar to other compostable polymers such as PBS & PBAT.

Wt % sc-PHB

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PLA/a-PHB Blends

Wt% M43000 10 20 30

Tg (°

C)

-40

-20

0

20

40

60

80

PLA Tg: Standard BlendsPLA Tg: Compatibilized BlendsM4300 Tg: Standard BlendsM4300 Tg: Compatibilized Blends

Two-Phase Structure Evident in Blends Component Tg largely unchanged

Wt % sc-PHB

PLA Tg PLA Tg a-PHB Tg a-PHB Tg

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PLA/a-PHB Blends

DSC Heating Scan @ 40 °C/minPost Cooling From the Melt @ 10 °C/min

Temperature (°C)-40 -20 0 20 40 60 80

Hea

t Flo

w [E

ndo −>

]

PLA: Tg ~ 50 °CM4300: Tg ~ -35 °C

Multi-Phase Morphology Two Distinct Phases

a-PHB:

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Pure

PLA

Biom

ax S

trong

120

Esta

ne 2

102

Blen

dex

3160

PBAT PBS

M41

00M

4300

M43

00 C

omp-

Blen

d

Izod

Impa

ct (f

t.lb/

inch

.)

0

2

4

6

8

10

Impact Benchmarking

All Polymeric Impact Modifiers

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Impact Benchmarking ONLY Compostable Impact Modifiers

Pure

PLA

PBAT PBS

M41

00

M43

00M

4300

Com

p-Bl

end

Izod

Impa

ct (f

t.lb/

inch

.)

0

1

2

3

4

5

6

a-PHB = Clear Winner

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Competitive Benchmarking

Modulus

Yield Strength

Break StrengthElongation

Izod Impact PLAPLA/PHAImpact PPPBTPC

/a-PHB

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Summary

PLA blends with a-PHB copolymer results in significant improvement in impact toughness with a modest decrease in modulus and strength. –Izod impact 0.4 -> 8.0 ft.lb/inch @ 20% a-PHB –NO compromise to biobased content and

compostability of PLA –Modulus-Strength-Toughness Balance

rivals that of polymers used in engineering applications!