The Journey of Poly(lactic acid):

From Commodities to Special

Applications

Saara Inkinen, Dr.Sc. (Tech.)

sinkinen@abo.fi

Senior Researcher, Laboratory of Polymer Technology, Åbo Akademi University

Technology Transfer Project Manager, Technology Transfer Office, Åbo Akademi University

FUNMAT Centre of Excellence

SAB meeting, Helsinki, 14. August 2013

Carbohydrates from plants

Lactic Acid

Poly(lactic acid) Lactic acid

and LA-based oligomers

Carbon dioxide and

water PLA

and the

Natural

Carbon Cycle

Fermentation

Polymerization ROP or step-growth

polymerization

Hydrolysis

Microbes

Photosynthesis

of plants

+ H2O

CO2 + H2O

• At the moment raw material needs do not compete with food production (Natureworks)

• In the future, if production increases, alternative sources from wastes and side-products should be

considered

Aliphatic polyester

Global trends in the use of PLA: • Production volumes of PLA continuously

increasing

• Growing Markets

• Numerous new application areas, both

biomedical and technical

• Further research needed especially for:

• Non-commodity applications e.g.

electronics

• Tailoring the hydrolytic and thermal

degradation rate

• Predicting life-span in long-term use

How has the LPT as part of FUNMAT contributed to this development?

Recent PLA research at LPT is related to: • Renewable, degradable adhesives

• Electronic applications

• Medical applications

• PLA modification possibilities

• Renewable coatings for paper and paperboard

• Degradation and stability studies, LCA

Highlights from Doctoral Thesis and

Other PLA Related Research

Dr. Saara Inkinen (Dissertation held Jan 2011)

Lactic Acid-Based Copolymers Having Different Molecular Architectures - Synthesis

Method: Step-growth

polymerization in melt

Benefits:

• Simple one step method

• potentially cheaper than

ROP

• Easy use of comonomers

Challenges:

• long polymerization time

• low Mw

• Repeatability

The synthesized polymers are suitable for e.g. hot melt adhesives,

stereocomplexes, and applications in which a high Tg is required.

Source: Saara Inkinen, Doctoral Thesis: Structural Modification of Poly(lactic acid) by Step-Growth

Polymerization and Stereocomplexation

Thermal Stability of PLA Copolymers Having Different Molecular Architectures

60 min isothermal heating at different

temperatures.

Molecular shape: linear linear branched linear branched Polymer type: LA homo- COOH-terminated OH-terminated polymer

Saara Inkinen, Geoffrey A. Nobes, Anders Södergård, Telechelic Poly(L-lactic acid) for Dilactide Production and Prepolymer Applications, 2011,

Journal of Applied Polymer Science, 119, 2602-2610.

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(m

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60 min isothermal heating at different

temperatures.

Molecular shape: linear linear branched linear branched Polymer type: LA homo- COOH-terminated OH-terminated polymer

Conclusions:

The structure and chain-end termination of low Mw PLA affects its tendency for

depolymerization and racemization, important for e.g. lactide production

Hydroxyl-terminated PLA depolymerizes quicker and more completely at elevated

temperatures and undergoes more racemization during polymerization

Saara Inkinen, Geoffrey A. Nobes, Anders Södergård, Telechelic Poly(L-lactic acid) for Dilactide Production and Prepolymer Applications, 2011,

Journal of Applied Polymer Science, 119, 2602-2610.

Thermal Stability of PLA Copolymers Having Different Molecular Architectures

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Copolymers of Lactic Acid and Isosorbide Increasing the Tg of PLA

Conclusions: The glass transition temperature (Tg) of PLA can be increased significantly

using isosorbide and a polyfunctional comonomer in combination with lactic acid.

• The Tg and the crosslinking density can be readily adjusted by varying the comonomer ratio and the

reaction conditions

• The polymer can be used at higher temperatures than conventional PLA without deformation

Saara Inkinen, Mikael Stolt, and Anders Södergård, Readily Controllable Step-Growth Polymerization Method for Poly(lactic acid) Copolymers Having a

High Glass Transition Temperature, Biomacromolecules, 2010, 11, 1196–1201.

Polymer type Tg (°C)

PLA having a high molecular weight (ROP) 60 - 65

PLA having a low molecular weight (step-growth

polymerization) 40 or lower

Copolymers of lactic acid, isosorbide and 1,2,3,4-

butanetetracarboxylic acid 80

Copolymers of lactic acid, isosorbide and 1,2,3,4,5,6-

cyclohexanehexacarboxylic acid 86

Isosorbide

PLA Stereocomplexes

Made by blending of PLLA and PDLA (melt, solvent casting, reactive

extrusion)

Stereocomplex (γ) crystals are formed at a 1:1 PDLA/PLLA ratio

Compared to PLA homopolymers, PLA stereocomplexes have

A higher melting point (up to 240

C)

Higher thermal stability and resistance to deformation

Higher hydrolytic stability

Better resistance to solvents

Stereocomplex crystals are not soluble even in good solvents for

conventional PLA

Better mechanical performance

These differences derive from the very strong physical interaction between

the L-lactoyl and D-lactoyl sequences in the crystal structure

PLA Stereocomplexes Stereocomplexes were prepared by blending of

1. linear and branched lactic acid-based PDLA that was prepared by step-growth polymerization or ROP and

2. PLA having a high molecular weight (prepared by ROP).

The melting point and enthalpy of the stereocomplexes was dependent on the molecular structure and especially the molecular weight of the PDLA component.

Melting point Melting Enthalpy Saara Inkinen, Mikael Stolt, Anders Södergård, Effect of blending ratio and oligomer structure on the thermal transitions of stereocomplexes

consisting of a D-lactic acid oligomer and poly(L-lactide), Polymers for Advanced Technologies, 22, 12, 1658–1664, 2011

Hydrolytic Degradation of PLA Stereocomplexes

• Stereocomplexes having a high molecular weight were exposed to aqueous environments (water or buffer)

• As compared to PLA homopolymer, the stereocomplexes had: • slower hydrolytic degradation rates • a more acidic degradation pattern • shorter degradation products due to the short tie chains between the crystals.

PLLA homopolymer PLLA/PDLA stereocomplex

ESI-MS (Electrospray ionization-mass spectrometry) –spectra after a 13 weeks degradation period in water at 60

C:

Sofia Regnell Andersson, Minna Hakkarainen, Saara Inkinen, Anders Södergård and Ann-Christine Albertsson, Polylactide Stereocomplexation Leads to

Higher Hydrolytic Stability but More Acidic Hydrolysis Product Pattern, Biomacromolecules, 2010, 11 (4), 1067–1073.

Customizing the Hydrolytic Degradation Rate of

Stereocomplex PLA through Different PDLA Architectures

Factors Studied: temperature, degradation time, and

amount and type of D-LA oligomer

Method: fractional factorial experimental design.

Conclusion:

• The degree of stereocomplexation and degradation

rate can be customized by changing the architecture

and end-groups of the D-LA oligomers.

Analysis methods: • SEM, ESI-MS, DSC, Mass

Loss, pH

Sofia Regnell Andersson, Minna Hakkarainen, Saara Inkinen, Anders Södergård, and Ann-Christine Albertsson, Customizing the Hydrolytic

Degradation Rate of Stereocomplex PLA through Different PDLA Architectures, Biomacromolecules, 2012, 13 (4), pp 1212–1222

Poly(lactic acid) Research at LPT, ÅAU

Recent Highlights

Recent Industrial Collaboration Related to Biopolymers and PLA

Kiilto Oy

Biodegradable Hot Melt Adhesives Prof. Carl-Eric Wilén

Dr. Saara Inkinen

M.Sc. Chen Tan

Novel Biopolymer

Coatings Assoc. Prof. Ari Rosling & group

M.Sc. Mohammad Khajeheian

M.Sc. Worker Ella Lindström

Bone and cartilage regeneration Doctoral student Peter Uppstu

Assoc. Prof. Ari Rosling & group

Dr. Saara Inkinen

Recent Research Related to Biopolymers and PLA

Rheological Modification of

Biopolymers by Radical

Generators Prof. Carl-Eric Wilén

M.Sc. Teija Tirri

Dr. Saara Inkinen

Ion Modulated Transistors on Paper Wide collaboration within FUNMAT,

including but not limited to:

Prof. Ronal Österbacka (Physics)

M.Sc. Fredrik Pettersson (Physics)

Dr. Tommi Remonen

Prof. Carl-Eric Wilén

Dr. Saara Inkinen

M.Sc. Marco Mennillo (starting Sep. 2013)

Other PLA Related Publications from the

FUNMAT CoE period

Review

• Saara Inkinen, Minna Hakkarainen, Ann-Christine Albertsson,

Anders Södergård, Review: From Lactic Acid to Poly(lactic

acid) (PLA): Characterization and Analysis of PLA and Its

Precursors, Biomacromolecules, 2011, 12 (3), pp 523–532

• Has been on the Biomacromolecules most read articles (12M) list since

spring 2011!

Book Chapter:

• Anders Södergård, Saara Inkinen, Book Chapter: Chapter 3

- Production, Chemistry and Properties of Polylactides, in

Biopolymers: New Materials for Sustainable Films and

Coatings / Wiley (Editor David Plackett), April 2011

New EU Project Starting: BIO4MAP

• Development of flexible and transparent fully biodegradable and recyclable

multilayer packaging for fresh pasta and cheese for applications requiring

customized Modified Atmosphere (MAP).

• Defining the requirements and structure of the semi-rigid multilayer

packaging designed for the products.

• Product validation at industrial scale in real conditions and shelf life tests.

• SME Project, Coordinator AIMPLAS, Valencia, Spain

• ÅAU Team: Prof. Carl-Eric Wilén, Dr. Saara Inkinen

Poly(lactic acid) Markets and

Future Perspectives Summary and Recent Application Examples

Biopolymers: Market Trends

Global Biopolymer Market

• PLA leading and strongest growing biopolymer

• Packaging largest application area

• Fibers/fabrics growing strongly

• Use in automotive applications expected to grow significantly

PLA: Market Trends

• Europe and Asia growing strongly, along with North America

• Packaging leading application area, growing strongly

• Use in fibers and fabrics strongly increasing

• Increase in the amount of other applications indicates broadening of

the application field of PLA

Use of PLA in Electronics: Examples

• Especially PLA composites and alloys show great promise in the field.

• Applications still limited due to factors related to its processing performance

and stability.

Biodegradable CD-ROM and

case made of PLA.

Picture Credit: Sanyo Mavic

Media PLA/Kenaf Biodegradable SD

Dummy Card

Picture Credit: NEC Corporation

Biobased PB Computer Case

Picture Credit: Fujitsu

Laboratories

Examples from: http://www.omnexus.com/resources/editorials.aspx?id=18461

Use of PLA in Automotive Applications:

Examples

• Main factors driving the use of biodegradable plastics in automotive

applications:

› Green image, reduced carbon footprint

› Reduced weight of the vehicle

• Automotive manufacturers interested both in:

› biodegradable and biobased polymers

› non-degradable polymers from annually renewable raw material sources

Use of PLA in Automotive Applications:

Examples

• Three main use areas:

1) interior components not having

demanding mechanical or other

requirements

2) parts becoming in contact with fuel

3) interior seating foams.

• Toyota and Ford are among the

largest companies that are using

bioplastics or biodegradable

polymers in automotive

applications.

Use of Ecological Plastic for

approximately 60% of an

automobile interior surface area

(http://www.toyota-boshoku.com)

The high price of PLA has repeatedly been reported as one of its disadvantages.

However, the price of PLA is nowadays comparable to the price of oil-

based plastics!

• Comparison, year 2011 (Ref. BCC Research):

› PLA $0.95-$1.30 per pound

› Polystyrene $1.07 per pound

› polyethylene at $0.95 per pound.

• Prices of PLA expected to decrease slightly over the next few years, reasons:

› improvements in manufacturing processes

› increased manufacturing scale

• Prices of oil-based plastics depend on and vary with the price of crude oil

• The cost of PLA depends on the price of corn (was high in 2011)

• However, e.g. Purac has used sugar beets as raw materials for lactic acid production

› Plans to use Cassava from Thailand

PLA Markets: Future Perspectives

Facts:

› If the demand of PLA grows faster than its production, prices will increase more than

projected.

› The opposite has been true in the past few years, as capacity has been larger than

demand and producers have decreased prices to increase sales. (Ref. BCC Research)

› PLA’s benefits do not justify its cost in all applications

The Big Questions:

› To what extent will the price of PLA depend on

the demand and the production cost?

› What are the key application areas PLA

research should focus on in the future, which

applications would bring the most benefit?

› Are there still undiscovered ”treasures” related to PLA, or just marginal improvements?

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3. Development still needed for example in terms of tailoring properties for

specific applications.

4. The PLA research conducted within is:

• Related to the most promising and growing application areas for PLA

• Internationally novel and collaborative

• Directly linked to the industry, increasing the direct economical and societal

benefits for Finland and Europe

• Scientifically interesting and, above all, FUN!

Conclusions

1. PLA production volumes and markets growing significantly.

2. New application areas emerging at an increasing speed, use of

stereocomplexes increasing.

Thank You! Saara Inkinen

saara.inkinen@abo.fi