Recent Developments on Polylactic acid

Recent Developments on Polylactic acid

Recent Developments on Polylactic acid

Yvon DurantAdvanced Polymer LaboratoryUniversity of New Hampshire

May 31st, 2006

May 31st, 2006 Research in renewable polymers 2

Leading the way toward greener chemistry

Poly Lactic Acid

what can it be used for ?

what is it ?

What’s the bid deal

Research involving PLA @ UNH

Degradable ties for fishing gear

Education software for the commercialization of PLA

PLA emulsions

Poly Lactic Acid

what can it be used for ?

what is it ?

What’s the bid deal

Research involving PLA @ UNH

Degradable ties for fishing gear

Education software for the commercialization of PLA

PLA emulsions


PLA end user products


What can it be used for….


Corn to PLA


PLA to Lactide

L-Lactic Acid

D-Lactic Acid

C

CHO

O

H OH

CH3

C

CHO

O

H OH

CH3

C

C

O

C

C

O

O

O

H

H

CH3

CH3

C

C

O

C

C

O

O

O

H

H

CH3

CH3

C

C

O

C

C

O

O

O

H

H

CH3

CH3

LL-Lactide

(mp 97 C)

LD-Lactide

(mp 52 C)

DD-Lactide

(mp 97C)


Cargill Dow PLA plant Nov 2001

The Blair projectNebraska

140 KT/Year


Inventory Analysis


Complete energy analysis


PLA versus other plastics


Process improvements


Potential reduction of greenhouse gasses associated with PLA

production

PLA research @ the University of New Hampshire ?


Figure 1: Concept of float for net release after 15 days water exposure

After 15 days, green composite tie, break down and releases float

Sealine Reducing right whale entanglement

Or “how can corn save whales”…


Develop a composite tie made from a polylactic acid (PLA) polymer matrix that will degrade after a controlled reaction with water.

Ties are being engineered to degrade after 15 days of exposure to seawater at 12C.

Ties will maintain optimal strength until 15 days of exposure has been reached.

Mechanical degradation is activated by a chemical amplification process that release protons, which catalyze the depolymerization of the polyester backbone.

How ?


Composite structure

Glass fibersPLA-co-GLA matrix Overlapping fibers

Microparticle – acid generator


Cascade degradation of PLA

Poly ester can break down through hydrolysis of the ester group

HO

O

O

O

O

OH

O

H O

H

HO

O

OH

O

O

OH

O

OH

O Cl O Me

OH2

O OH O Me

ClH

+ +

WATER


Variables Affecting Degradation Time

•Strain

• Tg

•Molecular weight

•Micro-capsule concentration


•Ties broke linearly with time according to strain

•Max strain extrapolated to be 5kg before exposure to sea water

After Exposure

Before Exposure

SAD065

0

1

2

3

4

5

6

0 1 2 3 4 5 6

time (days)

str

ain

(kg

)


Degradation PLA-ECL 90/10 with X-MACl at 12C in sea water

-10%

-9%

-8%

-7%

-6%

-5%

-4%

-3%

-2%

-1%

0%

0 5 10 15 20 25

Time (days)

We

igh

t lo

ss

(%

)

20000

21000

22000

23000

24000

25000

26000

27000

28000

29000

30000

Mo

lec

ula

r w

eig

ht

(Mn

g/m

ole

)

Degradation results


iComet

• iComet is a simulation software that is designed to be used as a training tool for technology managers.

• Two or more users or teams create virtual start-up companies to compete in the marketing and development of a new technology.

• Users must take the technology from the early stages of development to a level of high volume production over the course of twenty or more business quarters.

• Users must make strategic managerial decisions in the areas of finance, R&D, marketing, production, and HR in order to compete with the other teams and make their business successful.


Key technology : reduction of

energy usage


Multi domain decisions


Finances….


Results… earning some greens….

-20000000

-15000000

-10000000

-5000000

0

5000000

10000000

15000000

20000000

25000000

0 5 10 15 20 25

quarter

$

cash

earnings

commulative earnings

Return on Investment

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0 5 10 15 20 25

Quarter


PLA dispersionsPLA is a polyester and easily hydrolyzable. It cannot be

synthesized in water directly.2 classic approaches1. Bulk polymerization, dissolution in solvent,

emulsification, solvent evaporation2. Bulk polymerization, dissolution in solvent,

precipitation3 new approaches1. Bulk polymerization, dissolution in vinyl monomer,

mini-emulsification, polymerization2. Macromonomer, mini-emulsification, polymerization1. Polymerization in non-protique solvent, phase

transfer


Bulk recipesIngredients Recipe Distribution

DL-lactide 89% total monomer weightEpsilon caprolactone (ECL) 11% total monomer weightEthylene glycol (EG) 1% by mole of monomersStannous octoate 2% by mole of monomers

Ingredients Recipe DistributionDL-lactide 89% total monomer weightEpsilon caprolactone (ECL) 11% total monomer weightHydroxy ethyl methacrylate (HEMA) 0.2% by mass of monomersStannous octoate 1% by mass of monomers

High Molecular Weight PLA Polymer

Low Molecular Weight HEMA-PLA Macromer

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

1001,00010,000100,000

Mn g/mole - PS calibration

rid

1A/M

MD

macromer (HEMA-PLA)

low MW polyester (PLA)

• Dissolve PLA in solvent

• Miniemulsion in water stabilized with polyvinyl alcohol (PVA)

• Evaporate solvent via steam distillation

• GC/MS to quantify residual solvent

Steam distillation apparatus

Classic Approach 1: Solvent Evaporation

Solvents:

CH2Cl2

t-butyl methyl ether

isobutyl methyl ether


Classic Approach 2: precipitation

Dissolve PLA in THF –0.1 to 0.5 wt.%

Add to water/SDS dropwise through thin gauge needle under mechanical stirring

Results:

PLA dispersions (100-250nm)

Very low productivity


PLA magnetite


New approaches

Ingredients 1st Approach 2nd Approach 3rd ApproachHigh MW PLA 33wt% - -Low MW HEMA-PLA - 66wt% 95wt% methyl methacrylate (MMA) 33wt% - -butyl acrylate (BA) 33wt% - -styrene - 33wt% -Low MW PS - - 5wt%potassium persulfate (KPS) 3g/L total vol. 3g/L total vol. -azodiisobutyronitrile (AIBN) - - 1wt% sodium dodecyl sulfate (SDS) 4pph monomer 4pph monomer 2pph monomerdeionized water 30% solids 20% soilds 20% solids

Recipe Distribution


High MW PLA synthesis (70Kg/mole)

DL-lactide

Initiator: hexanol, Catalyst: SnOct2

Reacted in oven heated to 150oC for 2hrs

Miniemulsion Polymerization

Dissolve PLA in MMA and BA in 1:1:1 ratio

Magnetic stirring macro-emulsion

4pphm SDS

Ultrasonicated miniemulsion

Reacted in 3 neck jacketed reactor at 70oC for 3hrs with magnetic stirring and N2 feed

Initiator: 0.3 g/L KPS

New Approach 1: PLA/MMA/BA composite


Results for compositesRESULTS:

•47% conversion

•solids clumped around magnetic stirrer

•likely to be PLA

•NMR results showed less PLA, more acrylates in dry latex than in recipe


Low MW HEMA-PLA macro-monomer synthesis (5k)

DL-lactide

Initiator: HEMA, Catalyst: SnOct2



HEMA-PLA in minimal styrene


Aqueous phosphate buffer solution

4pphm SDS


Reacted in 3 neck jacketed reactor at 80oC for 3hrs with mechanical stirring and N2 feed

Initiator: 1 wt% KPS

O

OO

OO

O

n

OH

HEMA PLA

O

O

O

O

O

O

O

O

O

O

O

O

O O O O

O OO O

O

OH

O

OH

O

OH

O

OH

New approach 2: HEMA-PLA/PS branch


New approach 2: HEMA-PLA/PS branch

RESULTS:

• 22.4% conversion, 11% solids

• Tg 34oC dried latex

• NMR showed 1:4 ratio of PS to PLA, recipe gives 1:1 ratio

• Solid chunks in bottom of reactor


Low MW HEMA-PLA macro-monomer synthesis

DL-lactide

Initiator: HEMA, Catalyst: SnOct2



Heat HEMA-PLA until flows, add water


Aqueous phosphate buffer solution

4pphm SDS


Reacted in 3 neck jacketed reactor at 80oC for 3hrs with mechanical stirring and N2

Initiator: 1 wt% KPS

O

O

O

O

O

O

O

O

O

O

O

O

O O O O

O O O O

OO O O

OHOH OH OH

New approach 3: HEMA-PLA homopolymer


2nd Tgt = 20 min

1st Tgt = 0 min

-34.67°C(I)0.5342J/(g·°C)

-10.12°C(I)0.5642J/(g·°C)

3rd Tgt = 40 min

4th Tgt = 60 min

21.82°C(I)0.4118J/(g·°C)

23.56°C(I)0.4178J/(g·°C)

7th Tgt = 120 min

8th Tgt = 140 min

25.00°C(I)0.3292J/(g·°C)

9th Tgt = 160 min

9.58°C(I)0.4850J/(g·°C)

17.94°C(I)0.4520J/(g·°C)

5th Tgt = 80 min

6th Tgt = 100 min

-0.14

-0.12

-0.10

-0.08

-0.06H

eat F

low

(W/g

)

-60 -40 -20 0 20 40

Temperature (°C)Exo Up Universal V4.0C TA Instruments

Polymerization monitoring by DSC• Polymerization of HEMA-PLA with BPO• Alternating 80C isothermals – Temperature scans


Challenges

• Stability

• Viscosity of HEMA-PLA

• Low Tg of PLA

• Cross esterification of HEMA-PLA branches

• Degredation of HEMA-PLA while ultrasonicating with added heat

New approach 3: HEMA-PLA homopolymer


New approach 3: Dispersion Polymerization and Phase Transfer

Polymerization:

Heat lactide dispersion to 150oC in dispersion media- 3 neck RBF- submerged in oil bath, covered with tinfoil- Ultra turrax: 19.0 min-1

Add initiator (SnOct2 or mPEG), react 2hrs

Ultra turrax until cool: < 100oC

Phase Transfer:

Add water, 1:1 with organic phase

Stop ultra turrax, wait for phase separation

Separatory funnel to remove organic phase


Approach 3: Dispersion Polymerization and Phase Transfer

• Dodecane: = 0.4

Trial 1: stablilzed with PEG diasterate, transferred to EG, phase separated

Trial 2: stablilzed with PVOH, transferred to water, did not phase separate

• Silicone Oil: Stabilized with PEG diasterate

Poly phenyl methyl siloxane = 0 - most of lactide recrystallized, not able to centrifuge into water

Poly-3,3,3-trifluoro propyl methyl siloxane = (0.2) - appeared to be stable, congealed when cooled

• PEG dimethyl ether: Stabilized with mPEG, very stable, 20nm nanoparticles, try increasing solids, increasing initiator percentage to vary size


Acknowledgements

• Shelley Dougherty• Romuald Couronne

• Funding :– University of New Hampshire (iComet)– National Ocean and Atmosphere Agency (whale

entanglement)– New England Green Chemistry Consortium (novel

PLA dispersions)

Documents

Recent Developments on Polylactic acid