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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
© 2013 Metabolix 3
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
© 2013 Metabolix 4
PLA Toughening Approaches (1 of 8)
Plasticizers Mineral Fillers Traditional Impact Modifiers Other Compostable Polymers
© 2013 Metabolix 5
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.
© 2013 Metabolix 6
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
© 2013 Metabolix 7
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]
© 2013 Metabolix 8
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
© 2013 Metabolix 9
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.
© 2013 Metabolix 10
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
© 2013 Metabolix 11
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
© 2013 Metabolix 12
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)
© 2013 Metabolix 13
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
© 2013 Metabolix 14
sc-PHB Copolymers
Poly(3-hydroxy butyrate) homopolymer – Highly crystalline (~ 65%), high Tm (~ 160C)
With copolymers, control of Tg, Tm and crystallinity is possible.
© 2013 Metabolix 15
DSC of sc-PHB Copolymer
About 20% crystalline Low Tg phase
© 2013 Metabolix 16
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
© 2013 Metabolix 17
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
© 2013 Metabolix 18
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
© 2013 Metabolix 19
DSC of a-PHB
a-PHB is an amorphous, low-Tg rubber.
Cool at 10C/min
Heat at 40C/min
© 2013 Metabolix 20
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
© 2013 Metabolix 21
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
© 2013 Metabolix 22
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
© 2013 Metabolix 23
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
© 2013 Metabolix 24
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:
© 2013 Metabolix 25
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
© 2013 Metabolix 26
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
© 2013 Metabolix 27
Competitive Benchmarking
Modulus
Yield Strength
Break StrengthElongation
Izod Impact PLAPLA/PHAImpact PPPBTPC
/a-PHB
© 2013 Metabolix 28
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!
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