(2) P. Bachelet, S. Bourbigot, R. Delobel (3) D. Hottois, Ph. Coszach. (4) S. Solarski, M. Ferreira, ..... Philippe Dubois. ENSCL - PERF. Mr Pierre Bachelet.
From catalyzed polymerization of L,L-lactide (LA) to polylactide (PLA) filled composites: Key-performances conferred by stabilization and filler addition Dr. Eng. Marius Murariu
(LPCM - Prof. Ph. Dubois*)
*Center of Innovation and Research in MAterials & Polymers (CIRMAP), Laboratory of Polymeric and Composite Materials (LPCM), University of Mons-Hainaut Académie Universitaire Wallonie-Bruxelles, Mons, Belgium & Materia Nova asbl, Mons, Belgium
Workshop on DEGRADATION AND STABILIZATION OF POLYMER BLENDS, Palermo, 9 September 2007
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From catalyzed polymerization of L,L- lactide (LA) to polylactide (PLA) filled composites: Key-performances conferred by stabilization and filler addition (1) M. Murariu, A. Da Silva Ferreira, M. Alexandre, Ph. Degée, Ph. Dubois (2) P. Bachelet, S. Bourbigot, R. Delobel (3) D. Hottois, Ph. Coszach (4) S. Solarski, M. Ferreira, E. Devaux 1 - Service des Matériaux Polymères et Composites (SMPC), Université de Mons-Hainaut & Materia Nova, Place du Parc 20, 7000 Mons, Belgium 2 - Ecole Nationale Supérieure de Chimie (ENSCL) - laboratoire PERF, Avenue Dimitri Mendeleïev, 59652 Villeneuve d’Ascq Cedex, France 3 - Galactic s.a., Place d’Escanaffles 23, 7760 Escanaffles, Belgium 4 - Ecole Nationale Supérieure des Arts et Industries Textiles (ENSAIT), 59056 Roubaix Cedex 01, France
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Presentation Outline • INTRODUCTION “GREEN PERSPECTIVE“ : PLA • PRELIMINARY STEP: “STABILIZATION OF PLA AND PREPARATION OF AII FILLER” • HIGHLY FILLED PLA - AII COMPOSITES: “KEY-PERFORMANCES CONFERRED BY STABILIZATION AND FILLER ADDITION“ • CONCLUSIONS & ACKNOWLEDGEMENTS 3
INTRODUCTION
“GREEN PERSPECTIVE“ : PLA Global biodegradable polymer market by application: Source: BCC Inc.
Polylactic acid (PLA): currently accounts for 43% of the market
Source: BCC Inc.
(The Future Global Markets for Biodegradable Packaging report, source: www.PRW.com)
PLA by end use sector in 2005 Other 7% Fibres 23%
Annual growth rate of 12.6% to 206 million pounds in 2010. *Includes loose-fill packaging, which constitutes about two-thirds of the total. **Includes medical/hygiene products, agricultural, paper coatings, etc.
Packaging 70%
(Platt D., “Biodegradable Polymers Market Report”, Smithers Rapra Ltd., 2006)
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TYPICAL PLA APPLICATIONS
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Poly(lactic) acid cycle
Compost CO2, H2O
Glucose
Biomass
Lactic acid End products
PLA
Processing
Lactide
Lactide Polymerization* •Non-solvent process (ROP)
The starting material for PLA, lactic acid, is made by a fermentation process using 100% annually renewable resources.
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PLA- based composites filled with calcium sulfate from the lactic acid fabrication process ?
Carbohydrates (Renewable resources: sugar beets, corn starch….)
Fermentation
Lactic acid ( + Ca (OH)2)
Calcium lactate
Recovery and purification of lactic acid
H2SO4
For each kilogram of lactic acid, about one kilogram of gypsum is formed as co-product. (Mecking S. Angew. Chem. Int. Ed. 43(9), 2004; Narayanan N. et al., Electronic J. of Biotechn. 7(2), 2004)
Lactic acid
CaSO4 x 2H2O
L,L- lactide
Filling of PLA: Interesting solution to reduce its global price and to improve specific properties (rigidity, isotropic shrinkage,
Dehydration
CaSO4 x 0.5 H2O
Poly (L,L-lactide)
dimensional and thermal stability…)
By-product
250 ppm- max. content of water for PLA processing* Biodegradable polymer composites
(*Cicero J.A. et al., Pol. Degrad. Stab. 78 (2002) p.95; Hall ES. et al, U.S. Pat. No. 6,355, 772, 2002)
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Materials PLA (CREPIM) obtained by catalyzed polymerization of L,L-
LA* :
PLA (L3) - “un-stabilized” Characteristics : Mn (PLA) = 59,500; Mw/ Mn=2.0; residual monomer: 13% (determined by 1H NMR)
PLA (L5) - “stabilized” Characteristics : Mn (PLA) = 93,000; Mw/ Mn=2.2; residual monomer: 11% (determined by 1H NMR). * (Jacobsen S., Fritz H.G., Degée Ph., Dubois Ph., Jérôme R. Polymer, 41 (2000) p.3395; US 6,166,169, EP 0,912,624, WO 9,802,480 (Galactic) )
Filler: - β–calcium sulfate hemihydrate (CaSO4 x 0.5 H2O), d50 = 9 m (Galactic s.a.) To avoid extensive PLA hydrolysis, this β–calcium sulfate hemihydrate has to be previously dried at 500°C to obtain AII (β–anhydrite II).
Thermal stabilizers: - Ultranox 626A: Bis (2,4-di-t-butylphenyl) Pentaerythritol Diphosphite (GE Specialty Chemicals). - Weston TNPP: Tris (nonylphenyl) Phosphite (GE Specialty Chemicals). %- for all compositions will refer to weight percentage.
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MELT BLENDING TESTS WITH BRABENDER KNEADER: 190 C, (3 min premixing/30rpm, 3 min mixing/60rpm)
PLA* + AO
All components are dried before melt-blending
PLA(stab.) + AII To compression molding
Cam blades (moderate mixing)
Specimens made from plates
*PLA was dried overnight at 80 C (vacuum).
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“PRELIMINARY STEP :
STABILIZATION OF PLA AND PREPARATION OF AII FILLER”
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PLA stabilization - “state of the art” : excellent results using phosphites
Phosphites =
‘hydroperoxide decomposers’
TNPP
Ultranox 626A (King R.E., “Introduction to Polymer Stabilization”, American Chemical Society Meeting, San Diego CA (2001))
PLA stabilization: two ways 1. after polymerization 2. during reactive extrusion
Important: Phosphites are “chain extenders“ for PLA (Source: Cicero J.A. et al., Pol. Degrad. Stab., 78 (2002) p.95)
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TG (A) and d-TG (B) traces of PLA compositions with / without thermal stabilizers (under air flow, ramp 20C/min) 120
A
PLA (L3) PLA (L3)- 0.5% TNPP PLA (L3)- 0.5% Ultranox 826A
100
Stabilization of PLA : The principal step of degradation is shifted to higher temperatures.
3
B
60
2
1
40
0
20 100
200
300
400
Temperature (°C)
0
0
100
200
Deriv. Weight (%/°C)
Weight (%)
80
-1 500 Universal V3.9A TA Instruments
300
Temperature (°C)
400
500
600 Universal V3.9A TA Instruments
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Tensile strength at break of PLA (L3) compositions with/ without thermal stabilizers (ASTM D-638, v=1 mm/min, specimens type V, gauge length of 25.4 mm )
50 MPa
40 42
30
20
40
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10 PLA (L3)
PLA- 0.5% TNPP
PLA- 0.5% Ultranox 626A
Stabilized grades: increase of tensile strength at break as high as 40%. (Obs: also better impact properties)
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PLA stabilization: Evolution of PLA molecular weights upon melt-blending Sample
Mn (PLA)
P.I. (Mw /Mn)
- processed
59,500 19,000
2.0 3.3
Stabilization (post-polymerization) PLA (L3) - 0.5% Ultranox 626A
23,000
2.1
PLA (L3) - 0.5 % TNPP
28,500
2.1
PLA (L5) stab. during polymerization - before processing (granules) - after processing
93,000 47,000
2.2 2.0
PLA (L3)- without stabilizer - before processing (granules)
- Addition of stabilizer during polymerization: higher Mn, better stability. - A stabilized PLA grade is needed for filling.
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Preparation of filler for melt-compounding Two directions have been considered starting from gypsum hemihydrate:
(A) -anhydrite III (AIII) route (B) -anhydrite II (AII) route Calcium sulphate dihydrate
Drying in air, 140 C -Calcium sulphate
hemihydrate
200 C, air
(A)
500 C, air
-Calcium sulphate anhydrite III (unstable)
(B)
-Calcium sulphate anhydrite II (stable)
PLA
A
Melt-compounding Brabender kneader
B
PLA – gypsum composites for analyses
To avoid PLA hydrolysis: polymer and filler have to be previously dried.
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Selection of filler : anhydrite II (AII) vs. AIII Time dependence of water uptakes of β - anhydrite II and β - anhydrite III under atmospheric conditions 8 7
Water absorption, %
Anhydrite III
6
Anhydrite II
5 4 3 2 1 0 0
10
20
30 40 Time, minutes
50
(Murariu M., Da Silva Ferreira A., Degée P., Alexandre M., Dubois Ph. Polymer, 48 (2007) p.2613)
60
120
AII is stable☺ 16
HIGHLY FILLED PLA - AII COMPOSITES: “KEY-PERFORMANCES CONFERRED BY STABILIZATION AND FILLER ADDITION“
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Molecular parameters Evolution of PLA molecular weights upon melt blending Sample
Polydispersity index
Mn (PLA)
PLA (L5)*- granules
2.2
93,000
PLA (L5)- processed
2.0
47,000
PLA (L5)- 20% AII
2.2
57,000
PLA (L5)- 40% AII
2.4
59,500
*Stabilized during reactive extrusion of L,L- Lactide (0.3% Ultranox 626A)
No additional decrease of PLA molar mass (Mn) by AII addition.
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Thermal properties TG and d-TG traces of various PLA CREPIM (L5) compositions (under air flow, ramp 20C/min) 120
Stabilizing effect
5.5
? 4.5
Weight (%)
40% AII
40
PLA (CREPIM)- A II:
0
Addition of AII seems to confer better thermal stability
3.5 20% AII
2.5 0% AII
-40
1.5
PLA (CREPIM) PLA- 20% AII PLA- 40% AII
-80
-120
Deriv. Weight (%/°C)
80
0.5
0
100
200
300
Temperature (°C)
400
500
-0.5 600 Universal V3.9A TA Instruments
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TGA traces of various compositions for demonstrating the effect of AII into PLA (CREPIM)- AII compositions (under air flow, ramp 20C/min)
120 Weight, % AII
100 80
A II 60
PLA CREPIM V PLA - 40% AII
Theoretical curve
40 20
PLA (CREPIM)
Temperature, °C 0 0
100
200
300
400
500
600
Wth(PLA- 40%AII) = 0.6 w(PLA) + 0.4 w(AII)
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TGA traces of various compositions for demonstrating the effect of AII into PLA (CREPIM)- AII compositions (under air flow, ramp 20C/min) 120 Weight, % AII
100
Addition of filler =
80
A II PLA CREPIM V Theoretical curve Recorded curve
60 40
Stabilizing effect PLA - 40% AII
20 PLA (CREPIM)
Temperature, °C 0 0
100
200
300
400
500
600
Addition of AII into PLA: •Composites characterized by good thermal stability. •Presence of monomer/oligomers leads to better filler dispersion?
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Beneficial effect of filler addition and thermal stabilization for processing:
Weight modification in isothermal conditions (200 C, 60 min, under air)
A
105
(A) Effect of filler addition in stabilized PLA
250
Temperature 200
95 100
90
250
Temperature
0% AII 50
–––––– PLA CREPIM (L5)- 40% AII – – – PLA CREPIM (L5) 85
B 105
0
10
20
30
40
Time (min)
200
100
Stabilized 50
60
70
0
Universal V3.9A TA Instruments
150 95 Without stabilizer
100
Temperature (°C)
150
Weight (%)
Weight (%)
40% AII
Temperature (°C)
100
90 50
–––––– PLA CREPIM-40% AII (STABILIZED) – – – PLA-40% AII (UN-STABILIZED)
Important for processing: Excellent thermal stability of filled and stabilized grades.
85
0
10
20
30
40
Time (min)
50
0 70
60
Universal V3.9A TA Instruments
(B) PLA (CREPIM)- 40% AII: stabilized versus un-stabilized 22
Thermal properties DSC data on various PLA (L5)- CREPIM compositions χ*
Sample name
Tg (C)
Tc (C)/ Hc (J g-1)
PLA- CREPIM (processed)
55.5
97.6 (20.2)
154.6 (1.9)
171.6 (38.1)
17.2%
PLA (CREPIM)20% AII
58.9
101.1 (10.9)
157.4 (1.6)
174.1 (32.4)
21.4%
-
-
170.3 (38.9)
PLA (CREPIM)- ~54.6 40% AII
Tc (C)/ Tm (C) -1 Hc (J g ) Hm (J g-1)
Sec.
*Hm = 93 J/g for 100% crystalline PLA
41.8%
1
PLA (CREPIM)
0
Heat Flow (a.u.)
Addition of AII leads to compositions with higher crystallinity (χ) compared to pristine PLA.
Second heating from -10 to 220°C with a ramp of 10C/min
PLA - 20% AII
PLA - 40% AII -1
No cold crystallization 0.5 W/g
by addition of 40% AII filler -2 0 Exo Up
50
100
150
Temperature (°C)
200
250 Universal V3.9A TA Instruments
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Mechanical properties (tensile tests : ASTM D-638, v=1 mm/min, specimens type V, gauge length of 25.4 mm; impact tests : ASTM D256-A, specimens 60x10x3 mm, 3.46 m/s impact speed, hammer 0.668 kg)
PLA (L5)0% AII
PLA (L5)20% AII
PLA (L5)40% AII
Maximum tensile strength, MPa
57 2
49 1
38 2
Nominal strain at break, %
9.3 1.5
9.6 1.2
2.7 0.3
Young’s modulus, MPa
1150 160
1740 70
2160 160
Notched impact strength (Izod)
2.5 0.2
3.3 0.2
1.4 0.1
Parameters
•Increase of rigidity and attractive tensile strength properties.
AII filler particles as toughening agent ?? (Pluta M., Murariu M., Da Silva Ferriera A., Alexandre M., Galeski A., Dubois Ph. J. Polym. Sci. Part B Polym Phys. 2007 (accepted)).
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SEM pictures of the cryofractured surfaces of PLA- 20% AII (A) and PLA- 40% AII composites at low (B) and high magnification (C)
PLA- 20% AII
A
PLA- 40% AII
(1000x, 10 kV)
(1000x, 10 kV)
PLA- 40% AII •Well dispersed AII particles with various geometries and quite broad size distribution. •Even at relatively low shear, a surprisingly dispersion and aggregate breakdown.
B
C
(7000x, 10 kV).
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Conclusions •Packaging: big opportunity for bioplastics and PLA. •Addition of phosphites as thermal stabilizers: better- molecular, thermal and mechanical properties. •PLA can be melt-blended with thermally treated gypsum, by- product from the lactic acid fabrication process. •Filling of PLA (stabilized during polymerization): attractive thermal and mechanical properties, stability during processing. 26
Perspectives: up-scale applications
Excellent processing by injection molding
Potential application: biodegradable rigid packaging 27
MATERIA NOVA - SMPC Melle Amalia Ferreira Dr Michael Alexandre Dr Philippe Degée Mr Karl Berlier Prof. Philippe Dubois
ENSCL - PERF Mr Pierre Bachelet Dr Gaelle Fontaine Prof. Serge Bourbigot Prof. René Delobel
GALACTIC S.A. Melle Delphine Hottois Mr Philippe Coszach
ENSAIT - GEMTEX Dr Samuel Solarski Dr Manuela Ferreira Prof. Eric Devaux
We thank Dr Miroslaw Pluta (POLISH ACADEMY OF SCIENCES). We would like to thank Interreg III “France -Wallonie”, Régions Wallonne, Nord Pas de Calais and European Union (FEDER) for the financial support in the frame of interregional project MABIOLAC.
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Thank you !
Discussions, comments, questions……
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