Green PLA nanocomposites designed with special end-use properties - - PDF document

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“Green” PLA nanocomposites designed with special end-use properties (PowerPoint Presentation)

Conference Paper · May 2012

DOI: 10.13140/2.1.2504.4480

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Dr Dr. . Che Chem. . Eng.

• Eng. Marius

Marius MURAR MURARIU IU (Prof. Philippe DUBOIS)

Center of Innovation and Research in MAterials & Polymers (CIRMAP), Laboratory of Polymeric and Composite Materials,

Materia Nova Research Center, Mons & University of Mons, Belgium

Académie Universitaire Wallonie-Bruxelles

“Green” PLA na nano noco compo mposite sites de design signed ed with sp with spec ecial ial en end-use use pr prop

• per

erties ties

BiPoCo 2012

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“Green” PLA na nano noco compo mposite sites de design signed ed with sp with spec ecial ial en end-use use pr prop

• per

erties ties

(1) M. Murariu, A.-L. Dechief, L. Bonnaud, Ph. Dubois (2) A. Doumbia, M. Ferreira, C. Campagne, E. Devaux

1 Materia Nova Research Center & University of Mons, Avenue Copernic 1, Mons 7000, Belgium 2 Ecole Nationale Supérieure des Arts et Industries Textiles, Roubaix Cedex1, 59056, France

Follo

• llowi

wing ng th the e co coll llabo boration tion INT INTERR ERREG EG, NANOL ANOLAC C pr projec

• ject

Union Eu Européenne – Fonds Eu Européen de Dé Développeme ment Ré Régional INTE TERR RREG EG efface les frontières

Presentation outline

• INTRODUCTION: Biopolymers & PLA…
• Pathways to PLA - ZnO nanocomposites

designed for production of films and fibers

• CONCLUSIONS & ...

further works

Intr Introd

• duc

uction tion: : Ev Evolution

• lution of
• f mar

markets f ets for

• r biop

bioplastics lastics

(source: BCC Research; Bioplastics: Technologies and Global Markets (PLS050A) – Sept. 2010)

175 754 3230 572 500 1000 1500 2000 2500 3000 3500 2010 2015 Year ktonnes Europe Global market

Adapted, source: BCC Inc.

41.4% compound annual growth rate for bioplastics from 2010 through 2015

European Bioplastics association:

Global production capacity will double from 2010 to 2015

Number of worldwide patents per year linked to PLA

(source: Michel Biron, SpecialChem - May 10, 2011 )

In short time ˃ 400 patents/ year !

LAST TENDENCIES: From packaging & fibers to PLA products for technical applications

PLA grades with improved properties are required: impact & high tensile strength,

high HDT & long term durability, crystallization… PLA LA nan nanoco

• composites

mposites : : a a grea eat pot potent ential ial

5

Various types of nanoscale materials

(A.P. Kumar et al./ Progress in Polymer Science 34 (2009) 479–515)

PL PLA can A can be be suc succe cess ssfull fully y mo modified dified wi with th va variou rious s na nano nofil filler lers to s to ob

• btain

tain co compe mpeti titi tive e pr prop

• per

erti ties es

Our top of nanofillers:

1D : Organo modified clays, graphite derivatives (expanded and exfoliated graphite)… 2D : CNTs, cellulose nanowhiskers, Halloysite, Sepiolite… 3D : Ag, POSS, SiO2, CaCO3, AlO(OH)…

PLA is sensitive to shear, hydrolysis, thermo-oxidative degradation…

Some nanofillers & their treatment can lead to PLA degradation

ZnO

PATHWA

THWAYS S TO O PLA PLA - ZnO ZnO NANO ANOCOMP COMPOS OSITE ITES S DESIG DESIGNE NED D FOR FOR PR PRODUCTION ODUCTION OF OF FILMS FILMS AND AND FIBERS FIBERS WITH WITH SPECIAL SPECIAL END END-USE USE PR PROPER OPERTIES TIES

Sta State of te of t the Ar he Art t : ZnO nanofillers mixed with different polymers (PA 6, epoxy and acrylic resins, PMMA, PS...): antibacterial function, intensive ultraviolet absorption, other characteristic features. ..

PLA-ZnO nanocomposites, no relevant information

The catalytic depolymerization ability of Zn-based products (ZnO) :

the main reason explaining the lack of studies concerning the PLA-ZnO nanocomposites.

(Murariu M, Doumbia A, Devaux E, Dubois Ph. et al., Biomacromolecules 2011, 12: 1762–71)

(Gaur MS, et al., J. Appl. Polym. Sci. 2010;118:2833-40; Agrawal M, et al., Macromol. Chem. Phys. 2010;211:1925-32)

(Abe, H et al., Biomacromolecules 2004, 5: 1606-14)

PLLA O C O CH CH3 O C O CH CH3 O C O CH CH3 O Zn PLLA O C O CH CH3 O C O CH CH3 O C O CH CH3 O Zn PLLA O C O CH CH3 O Zn PLLA O C O CH CH3 O C O CH CH3 O C O CH CH3 O C O CH O CH3 C CH O CH3 O O CH C O CH C O CH3 CH3 O PLLA O C O CH CH3 O Zn O CH C O CH C O CH3 CH3 O

+

a

PLLA O C O CH CH3 O C O CH CH3 O C O CH CH3 O Zn PLLA O C O CH CH3 O Zn

+

Zn

b

Transesterification (a) and “unzipping” depolymerization (b) reactions of PLA in presence of Zn compounds

(adapted from Abe, H et al.,. Biomacromolecules 2004, 5: 1606-14 )

ZnO as well as other Zn compounds have been successfully utilized as effective catalysts for lactide polymerization and also in “unzipping” depolymerization of PLA and lactic acid oligomers (OLA).

(Xiao-Gang Yang et al., Polymer Bulletin 2008, 61: 177–88)

a b

8

Examples to illustrate the application

• f anti-bacterial products

Antibacterial fibers

Electronics, washing machines, refrigerators, air conditioners & purifiers, vacuum cleaners…

Water Treatment , Purifications Health Care Industry Electronics & Communications Textile & Clothing Industry Painting Industry Agriculture Cosmetic Industry Soft Drinks Industry Shoes Industry Aerospace Industry Consumer Products Packaging Industry Automotive Industry Military And Government Services

Pol

• ly(L,L

y(L,L-lact lactide ide) ) (PLA) (PLA) - “Na Natu tureW eWor

• rks

ks” PLA1 (grade for films/ 4032D) : Mn(PLA) = 88 500; Mw/ Mn=1.8; D-isomer: <2%. PLA2 (grade for fibers*/ 6201D) : Mn(PLA) = 55 000; Mw/ Mn=1.9; D-isomer: 1.4%. Ultranox 626A (U626): Bis (2,4-di-t-butylphenyl) Pentaerythritol Diphosphite ZnO, rod-like nanoparticles : Umicore Zinc Chemicals Zano 20 : Bulk density: 280 g/l, Specific surface area BET : 25 - 35 m2/g (noted as ZnO). Zano 20 Plus : surface treated with triethoxy caprylylsilane, bulk density: 360 g/l, loss

• n drying at 105°C (2h): max. 1%; ZnO content: 96.2 ± 0.5%; (noted as ZnO(s)).

%- for all compositions will refer to weight percentage.

Ma Mater terials ials

“Rods” of ZnO(s) (length up to 100 nm, diameter of ~15-30 nm)

ZnO

* PLA 6202D (D-isomer ≈ 2%), spinning grade was also used for up- scaling in production of fibers 10

• I. Stearates as coating agents

I.

• I. Surface coating of ZnO with up

3% of selected stearates (Zn

• r Mg) does not lead to some

improvements of properties:

low tensile strength or breakable plates after compression molding. PLA1- 2% ZnO (treated with Mg stearate)

Triethoxy caprylyl silane: especially suitable for the treatment of metal oxides (ZnO), very stable coating.

II II. . Sil Silanes anes To make PLA less susceptible to the catalytic action of ZnO surface treatments with selected additives ZnO vs. ZnO(s) in PLA-ZnO nanocomposites

(source: www.koboproducts.com)

Melt-blending at small scale with Brabender kneaders:

190-200C (3 min premixing/30rpm, 7 min mixing/70rpm)

All components are dried before melt-blending PLA was dried overnight at 80C (vacuum)

PLA PLA + + na nano nofil filler ler + + ad additiv ditives* es*

To compression molding

Additional processing by injection molding

U626 was used in preferred percentage of 0.3 wt-%

Testing

Plates for realization of specimens by cutting

12

The modification of molecular parameters (Mn (a) and PI (b)) of PLA1 and PLA2 with different loadings of surface-treated or untreated ZnO

Even in presence of surface-treated ZnO(s) it is not possible to completely avoid the degradation of the polyester matrix.

The surface-coating of ZnO allows for limiting the decrease of PLA molecular weights

(more evident in the case of PLA2)

Thermal properties of PLA1 and of PLA2 at different loadings

• f surface-treated or untreated ZnO nanofiller

(under air, 20 °C/min)

322 322 294 294 277 277 241 241 PLA2 PLA2 -

• 3%

3% ZnO ZnO 8 8 338 338 297 297 285 285 251 251 PLA2 PLA2 -

• 2%

2% ZnO ZnO 7 7 336 336 301 301 283 283 253 253 PLA2 PLA2 -

• 1%

1% ZnO ZnO 6 6 368 368 328 328 PLA2 PLA2 (0% (0% ZnO ZnO) ) 5 5 327 327 299 299 275 275 252 252 PLA1 PLA1 -

• 3%

3% ZnO ZnO 4 4 332 332 304 304 285 285 256 256 PLA1 PLA1 -

• 2%

2% ZnO ZnO 3 3 339 339 313 313 289 289 266 266 PLA1 PLA1 -

• 1%

1% ZnO ZnO 2 2 381 381 337 337 PLA1 PLA1 (0% (0% ZnO ZnO) ) 1 1 ZnO(s ZnO(s) ) ZnO ZnO ZnO(s ZnO(s) ) ZnO ZnO Temperature of the maximum rate of degradation, °C (from D-TG) Temperature for 5% weight loss, °C Sample composition Sample composition ↓ ↓ (wt (wt-

• %)

%) Nanofiller Nanofiller type type → → Entry Entry 322 322 294 294 277 277 241 241 PLA2 PLA2 -

• 3%

3% ZnO ZnO 8 8 338 338 297 297 285 285 251 251 PLA2 PLA2 -

• 2%

2% ZnO ZnO 7 7 336 336 301 301 283 283 253 253 PLA2 PLA2 -

• 1%

1% ZnO ZnO 6 6 368 368 328 328 PLA2 PLA2 (0% (0% ZnO ZnO) ) 5 5 327 327 299 299 275 275 252 252 PLA1 PLA1 -

• 3%

3% ZnO ZnO 4 4 332 332 304 304 285 285 256 256 PLA1 PLA1 -

• 2%

2% ZnO ZnO 3 3 339 339 313 313 289 289 266 266 PLA1 PLA1 -

• 1%

1% ZnO ZnO 2 2 381 381 337 337 PLA1 PLA1 (0% (0% ZnO ZnO) ) 1 1 ZnO(s ZnO(s) ) ZnO ZnO ZnO(s ZnO(s) ) ZnO ZnO Temperature of the maximum rate of degradation, °C (from D-TG) Temperature for 5% weight loss, °C Sample composition Sample composition ↓ ↓ (wt (wt-

• %)

%) Nanofiller Nanofiller type type → → Entry Entry

PLA/ZnO(s) : T5% and TD at significantly higher temperature (from 20 to 40°C with respect to the samples containing untreated nanofiller)

(Murariu M, Doumbia A, Devaux E, Dubois Ph. et al., Biomacromolecules 2011, 12: 1762–71)

TGA in isothermal conditions (air) of PLA2 with different loadings

• f surface-treated or untreated ZnO at 200 °C (a) and 220 °C (b)

The nanocomposites containing ZnO(s) proved to be obviously more stable.

Shielding effect conferred by the

• rgano-silane layers (Zn-O-Si-R) and

–Si-O-Si- network formation

After 30 min at 220°C PLA1 and PLA2 containing 3% ZnO show a weight loss as high as 32% and 44% !

a b

(Murariu M, Doumbia A, Devaux E, Dubois Ph. et al., Biomacromolecules 2011, 12: 1762–71)

Evolution of tensile strength (a) and Young’s modulus (b) of PLA1 compositions with different loadings of surface-treated or untreated ZnO

(tensile tests : ASTM D-638, v=1 mm/min, specimens type V, gauge length of 25.4 mm)

Strong decrease of tensile strength (~ 50 %) by addition of 2 to 3 % untreated nanofiller (ZnO).

The increase in the stress using ZnO(s) indicates that PLA/ZnO interface is tuned by treatment with silane. For both matrices, Young’s modulus increases with the relative content in nanofiller (ZnO or ZnO(s))

Comparative mechanical properties of PLA2 (NW 6201D) and PLA2– ZnO(s) nanocomposites (standard deviations are given in brackets)

(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)

Entry Sample (%, by weight)

• Max. tensile

strength, MPa Young’s modulus, MPa Nominal strain at break, %* Impact strength Izod, kJ/m2 1 PLA2 (0% ZnO(s)) 61 (±2) 2100 (±150) 6.3 (±0.5) 2.7 (±0.2) 2 PLA2 - 1% ZnO(s) 58 (±1) 2250 (±100) 4.4 (±0.2) 2.8 (±0.2) 3 PLA2 - 2% ZnO(s) 59 (±4) 2150 (±150) 5.2 (±0.3) 2.7 (±0.2) 4 PLA2 - 3% ZnO(s)) 57 (±3) 2600 (±150) 3.7 (±0.2) 2.9 (±0.4)

For loadings of 1-3 % ZnO(s) good tensile strength, the notched impact strength (Izod) of the nanocomposites is comparable to those of neat PLA. The mechanical characterization of nanocomposites having PLA2 as matrix (lower Mn) was not possible.

Preliminary conclusion

PLA2: PLA NW 6201D grade for fibers

Surface-treated ZnO(s) by triethoxy caprylylsilane is leading to PLA nanocomposites characterized by better morphology & performances.

Some clusters/aggregates

• f ZnO nanofillers

Finer dispersion and distribution of ZnO(s)

(Murariu M, Doumbia A, Devaux E, Dubois Ph. et al., Biomacromolecules 2011, 12: 1762–71)

(3) Granulating (granules for spinning or extrusion of films)

(2) Melt compounding in twin- screw extruder Leistritz type ZSE 18 HP-40D (Ø=18mm, L/D=40)

Gravimetric dosing systems integrated on extruder

(1) PLA* + ZnO(s) (dry mixing)

* PLA 4032D (film extrusion grade) / 6201D, 6202D (spinning grades)

Up-scaling of PLA*- ZnO(s) nanocomposites for films and fibers designed with specific end-use properties

Selected example: TEM pictures at different magnifications of PLA2*–1% ZnO(s) Typically, good nanofiller dispersion is obtained after the melt- compounding using twin-screw extruders

*PLA2= PLA NW 6202D

20

PLA-ZnO masterbatch (MB): new approach in realization of PLA-ZnO(s) nanocomposites with improved properties (preliminary results)

Even in presence of surface-treated ZnO(s) it is not possible to completely avoid the degradation of PLA matrix. Better properties limiting the residence time at high temperature of PLA in presence of ZnO(s) nanofiller

PLA granules

(Grade for extrusion)

Melt-compounding

(Twin-screw extruder)

Granulating (Drying)

PLA – ZnO masterbatch

2 1

Dosing in twin-screw extruder (gravimetric feeders)

ZnO (up to 40 wt-%)

(Zano 20 Plus)

Semi-finished products

CARACTERIZATION

3 4

Blending with neat PLA

New approach: realization and utilization of PLA- ZnO MBs For the first time (?) realization of highly filled PLA-ZnO MBs !

MBs with up to 40% ZnO(s) : melt-compounding using a

twin-screw extruder Leistritz (ZSE 18 HP-40D, Ø=18mm, L/D=40).

22

TGA of PLA-ZnO(s) MBs

20 40 60 80 100 120

Weight (%)

100 200 300 400 500 600

Temperature (°C)

MB20 MB30 MB40

Universal V3.9A TA Inst

(under air flow, ramp 20 °C/min)

No important differences between the thermal stability of MB samples, addition of special thermal stabilizers/additives is already considered.

Sample Temperature for 5% weight loss, °C Temperature of the

• max. rate of

degradation*, °C MB20 278 308 MB30 273 301 MB40 270 302

As expected, lower thermal stability by comparing to the neat PLA (T5% ~ 330 °C)

No dramatic decrease of PLA thermal stability using up to 40% ZnO silane treated !

23

Comparative DSC thermograms of PLA- (10-30)% ZnO(s) MBs

First DSC heating on granules Second DSC heating

• 1.5

1.5

Heat Flow (a.u.)

• 20

30 80 130 180

Temperature (°C)

MB 10% MB 20% MB 30%

Exo Up Universal V3.9A TA

(first and second DSC heating, 10 °C/min)

Granules of PLA-ZnO MB: Degree of crystallinity higher than 30% ! Tm Tg Tc DSC: Stability of principal thermal parameters

24

Comparative evaluation of different approaches in realization of films

A) Utilization of PLA- 1% ZnO(s) granules PLA (~ 99%) is in contact with ZnO(s) (1%) for long time at high temperature, shear, etc.☻ B) Utilization of PLA- 40% ZnO MB ☺ 97.2 wt-% is virgin PLA (short residence time in molten phase in presence of ZnO(s))

To obtain a film (PLA- 1% ZnO) :

98.7% PLA- (0.3% U626) - 1% ZnO(s) 97.2% neat PLA (0.3% U626) – 2.5 % MB

granules (nanocomposite)

B

MB MB APPR APPROACH: A SHORTER RESIDENCE TIME of PLA in presence of ZnO(s) (high specific surface 25-35 m2/g) !

A

(Obs: only 1.5% PLA (from MB) has longer thermal history)

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Parameter PLA1- 1% ZnO(s) (granules) MB technique Speed of screw, rpm 12 12 Torque, Nm 20 110 Pressure, bars 3 50 Relative viscosity* in chloroform of PLA1 nanocomposites from films by comparing to neat PLA1 (AR) (25 °C, 1g/100 ml)

MB

Better molecular parameters & processing using MB way ascribed to higher melt viscosity

MB MB

°Due to the presence of nanofillers, for the protection of GPC/SEC columns, it was preferred to perform analyses of viscosity in solution (to be further discussed). Brabender single screw extruder (Ø=19mm, L/D=25)

26

TGA of PLA1 – ZnO(s) films obtained using different techniques (under air flow, 20 C/min)

Sample (%, by weight) Temperature for 5% weight loss, °C Temperature for 50% weight loss, °C Temperature of the max rate of degradation, °C PLA – 1% ZnO(s) 285 333 343 PLA – 1% ZnO (MB40) 297 333 340 PLA – 2% ZnO(s) 272 312 320 PLA – 2% ZnO (MB40) 300 336 342 PLA – 3% ZnO(s) 274 312 321 PLA – 3% ZnO (MB40) 294 329 335

Improved thermal parameters for films obtained using MB technique.

DSC: not important thermal differences (Tg and Tm).

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Evolution of tensile strength (A) and Young’s modulus (B) of PLA1 and PLA1 – ZnO(s) films

(v= 1 mm/min, distance between grips of 25.4 mm; specimens 64x10x~0.4 mm3)

Films with good tensile strength* properties, higher strain at break, somewhat higher rigidity using the MB approach

Slight increase of PLA Young’s modulus with the relative content in nanofiller

A B

* Improvements in tenacity were more important in production of fibers

TEM pictures at different magnifications of PLA1– 1% ZnO(s) films obtained using the MB approach

Good nanofiller distribution/dispersion using a highly filled MB (≈ 40% ZnO) and a single screw extruder

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PLA-ZnO(s) nanocomposites (films & fibers): specific end-use properties

PLA – ZnO(s) nanocomposites tested in production of films (a) and fibers (b).

Spinning

a b

PLA1-ZnO(s) PLA2-ZnO(s)

30

UV-vis spectra of PLA1 and PLA1 – ZnO(s)* films

(0.10-0.15 mm thickness, DSM film device)

CONFIRMATION: ZnO nanofiller is

absorbing the harmful UV radiation

10 20 30 40 50 60 70 80 90 200 300 400 500 600 700 800 Wavelength (nm) Transmittance (%)

PLA PLA- 0.3% U626A PLA- 0.5% ZnO Plus PLA- 1% ZnO Plus PLA- 2% ZnO Plus

*all PLA-ZnO samples contain 0.3% U626A

PLA1- 3% ZnO(s): According to

JIS Z 2801*, good antibacterial activity against gram positive bacteria (S. aureus)

Formation of “reactive species” can require longer time…

Good antibacterial activity (after 7 days) against both, gram negative and gram positive bacteria** Antibacterial properties on films

(*Remark: this is a rapid test (24 h)) **Giuliana G. et al., PLA-ZnO nanocomposite films: water vapour barrier properties and key characteristics (in preparation)

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PLA PLA- ZnO ZnO(s) (s) na nano noco compo mposite site fiber fibers*: s*: an anti tiba bacte cteri rial perf al perfor

• rman

mance ce

Antibacterial specific activity on knitted fabrics* towards Staphylococcus aureus (gram positive) and Klebsiella pneumoniae (gram negative) bacteria

**Activity (A) superior to 2.0 reduction in bacteria number > 99 %.

18 h, 37°C Good antibacterial performance** by addition of 3% ZnO(s) into PLA2

(*by courtesy, results obtained from Dr. Awa Doumbia –ENSAIT Roubaix, France)

(source: HEIQ)

JIS L 1902

• New PLA/ZnO nanocomposites designed for films and fibers:

ZnO silanization proved necessary to limit the decrease of PLA molecular and thermal parameters.

• Nanocomposites showing good nanofiller dispersion and mechanical

properties, anti-UV protection, antibacterial performances…

• PLA/ZnO MBs : a promising approach to improved products

better thermo-mechanical and molecular parameters, optimistic nanofiller dispersion, specific end-use performances…

Conclusions & perspectives

• Synergies between ZnO and Ag nanoparticles, other nanofillers…
• Effect of ZnO addition on the photo-oxidative degradation of PLA matrix

(collaboration with Blaise Pascal University – Clermont-Ferrand, France)

• Investigations of transport properties on films (University of Salerno – Italy)

PERSPECTIVES & additional studies

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We would like to thank Interreg “France -Wallonie”, Régions Wallonne, Nord Pas de Calais and European Union (FEDER) for the financial support in the frame of interregional project NANOLAC.

MATERIA NOVA – SMPC Miss Anne-Laure Dechief Mr Yoann Paint Mr Karl Berlier Dr Leila Bonnaud Prof Philippe Dubois ENSCL - FRANCE Dr Antoine Gallos Dr Gaelle Fontaine Prof Serge Bourbigot ENSAIT - FRANCE Dr Awa Doumbia Dr Christine Campagne Dr Manuela Ferreira Prof Eric Devaux

Union Eu Européenne – Fonds Eu Européen de Dé Développeme ment Ré Régional INTE TERR RREG EG efface les frontières

UMICORE Zinc Chemicals Catherine Leroy Jeroen Van Den Bosch

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Mons in Belgium…

Thank you for your attention !

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