Green ionic liquids for the production of fully-biobased and biodegradable all-cellulose nanocomposites

(1)

Benoît Duchemin, Aji Mathew and Kristiina Oksman

Division of Manufacturing and Design of Wood and Bionanocomposites Luleå University of Technology

Green ionic liquids for the production of fully biobased and biodegradable

all-cellulose composites

10^th International Conference on Wood and Biofiber Plastic Composites &

Cellulose Nanocomposites Symposium, Madison, Wisconsin, USA.

(2)

Future Trends in Packaging Materials All-cellulose composites

• Fully biobased and biodegradable composite material composed solely of cellulose.

• Manufactured by:

– (i) mixing fully dissolved cellulose and undissolved cellulose

– (ii) by consolidating partially dissolved cellulose.

• The material needs to be regenerated (precipitated) and dried.

• Excellent mechanical properties.

(3)

Future Trends in Packaging Materials Outline

• Background:

– General idea

– Partial dissolution

– Comparison with other materials – Solvents

• Experimental procedures:

– Materials

– Characterization – Manufacturing

• Results:

– XRD

– Mechanical properties – SEM

– DP

• Conclusions

– Schematic

– General remarks

(4)

Future Trends in Packaging Materials The philosophy behind all-cellulose composites

Matrix Reinforcement

Composite Regenerated cellulose obtained by cellulose dissolution, insuring

excellent interfacial chemical bonding

Natural fibre from ramie, wood pulp, rice husk, MCC, BC, etc

Cellulose I crystallites: E

cellulose I

> E

cellulose II

Regenerated fibre:

high-strength, high modulus, high orientation fibres

Ecellulose I (GPa) 138 90

Ecellulose II (GPa) 88 75

Author Nishino 1995 Ishikawa 1997

(5)

Future Trends in Packaging Materials

Manufacturing by partial dissolution: step 1

 Crystallites ~3-7 nm initially present in the material.

 Non-crystalline phase surrounding the crystallites and making the microfibrils.

 Solvent

(6)

Future Trends in Packaging Materials

Manufacturing by partial dissolution: step 2

 Crystallites

 Non-crystalline phase

 Solvent

 Dissolved cellulose

(7)

Future Trends in Packaging Materials

Manufacturing by partial dissolution: steps 3 and 4

 Crystallites

 Dissolved cellulose

 Precipitation medium

 Regenerated

cellulose

(8)

Future Trends in Packaging Materials What all-cellulose composites are not

• Tracing paper

• Vulcanized paper

• Cellophane

• Regenerated films from NMMO

Specialty papers

Regenerated cellulose

(9)

Future Trends in Packaging Materials

2 4.5 7 9.5 20

5 1 13 9

17

0 100

200 300 400

Strength (MPa)

Strain (%) Young's

modulus (GPa)

Mechanical properties of all-cellulose composites compared

Regular paper, GF weave/epoxy, regenerated cellulose films, MFC composites (low resin content),

nanofibrillated cellulose paper, all-cellulose composites

(10)

Future Trends in Packaging Materials

2 4.5 7 9.5 20

5 1 13 9

17

0 100

200 300 400

Strength (MPa)

Strain (%) Young's

modulus (GPa)

Mechanical properties of all-cellulose composites compared

Regular paper, GF weave/epoxy, regenerated cellulose films, MFC composites (low resin content),

nanofibrillated cellulose paper, all-cellulose composites

(11)

Future Trends in Packaging Materials

2 4.5 7 9.5 20

5 1 13 9

17

0 100

200 300 400

Strength (MPa)

Strain (%) Young's

modulus (GPa)

Mechanical properties of all-cellulose composites compared

Regular paper, GF weave/epoxy, regenerated cellulose films, MFC composites (low resin content),

nanofibrillated cellulose paper, all-cellulose composites

(12)

Future Trends in Packaging Materials

2 4.5 7 9.5 20

5 1 13 9

17

0 100

200 300 400

Strength (MPa)

Strain (%) Young's

modulus (GPa)

Mechanical properties of all-cellulose composites compared

Regular paper, GF weave/epoxy, regenerated cellulose films, MFC composites (low resin content),

nanofibrillated cellulose paper, all-cellulose composites

(13)

Future Trends in Packaging Materials

2 4.5 7 9.5 20

5 1 13 9

17

0 100

200 300 400

Strength (MPa)

Strain (%) Young's

modulus (GPa)

Mechanical properties of all-cellulose composites compared

Regular paper, GF weave/epoxy, regenerated cellulose films, MFC composites (low resin content),

nanofibrillated cellulose paper, all-cellulose composites

(14)

Future Trends in Packaging Materials

The greenness of all-cellulose composites...

...is determined by the choice of solvent

Factors Efficiency Temperature Viscosity Recyclability Hygroscopicity V.O.C. Pre-treatment Toxicity

LiCl/DMAc

Ionic liquids (*)

(*): BmimCl (a.k.a. [C₄mim]Cl), BmimBr, BmimSCN, BmPyCl, AmimCl, EmimAc, EmimDEPO₄…

(15)

Future Trends in Packaging Materials Outline

• Background:

– General idea

– Materials

• Results:

– XRD

– DP

• Conclusions

– Schematic

– General remarks

(16)

Future Trends in Packaging Materials Materials

• Whatman filter paper grade 40 (95 g/m

²

, ash content < 0.007%) from cotton linters, DP = 1240.

• Microfibrillated cellulose

(Daicel chemicals, lot # 75203) from wood pulp, vacuum filtered and hot pressed at 100°C and 1.5 MPa, DP = 1000.

• 1-butyl-3-methylimidazolium

chloride, [C

₄

mim]Cl, 95% purity,

BASF.

(17)

Future Trends in Packaging Materials Characterization

• Mechanical testing: Shimadzu Autograph AG-X, 55% R.H., 20 °C, 1 mm/min, 20 mm gage length.

• X-ray diffraction: Siemens D5000, Cu K_α source (λ = 0.15418 nm), 40 kV acceleration voltage and 40 mA current. CrI calculated using Segal's method (1959).

• Scanning electron microscopy: Jeol JSM 6460LV, 10 kV

acceleration voltage, samples gold coated and mounted on carbon tabs.

• Degree of polymerization: dissolution in 4.6 wt.% LiOH/15 wt. % urea (Cai 2006).

(18)

Future Trends in Packaging Materials Preparation

• Thorough drying at 103ºC

• Immersion of MFC or filter paper in [C

₄

mim]Cl

• Dissolution at 80ºC for a time t

• Cooling for 1 hr at room conditions

• Water exchange for 2 * 24 hr at room temperature

• DI water rinsing

• Drying in a vacuum bag, 60ºC overnight and

pressure < 0.1 atm.

(19)

Future Trends in Packaging Materials Outline

• Background:

– General idea

– Materials

• Results:

– XRD

– DP

• Conclusions

– Schematic

– General remarks

(20)

Future Trends in Packaging Materials XRD: Filter paper

• Initially: highly crystalline cellulose I.

• Broadening of the (200) peak indicative of

dissolution.

• Broadening increases with dissolution time.

• (200) peak of cellulose I at ca. 22.8° remains

throughout the

transformation.

(21)

Future Trends in Packaging Materials XRD: MFC

• Initially: highly

crystalline cellulose I.

• Slight broadening of the (200) peak

indicative of limited dissolution.

• Cellulose I allomorph clearly remains

throughout the

transformation.

(22)

Future Trends in Packaging Materials XRD: CrI changes

• Only very limited change for MFC.

• More drastic decrystallization occuring for filter paper.

MFC

Filter paper

(23)

Future Trends in Packaging Materials Mechanical properties

• More spectacular changes could be observed for FP (□) than for MFC (■).

• MFC performed the best in terms of tensile strength and stiffness.

+560 %

+300 % +10 %

+20 %

+100 %

decrease

(24)

Future Trends in Packaging Materials SEM: filter paper

Microfibrillar structure

(initially)

Fully consolidated structure (160 min

dissolution)

(25)

Future Trends in Packaging Materials SEM: MFC

Submicron fibrillar structure

(initially)

Partially

consolidated, “skin-

core” morphology

(160 min dissolution)

(26)

Future Trends in Packaging Materials Degree of polymerization

Legend

&

Estimated DP

Filter

paper MFC

NoDissolution

■

1240 ▼ 1000

160 min

dissolution

♦

720 ▲

590 The DP is

reduced by ~40% !

[η]

(27)

Future Trends in Packaging Materials Outline

• Background:

– General idea

– Materials

• Results:

– XRD

– DP

• Conclusions

– Schematic

– General remarks

(28)

Future Trends in Packaging Materials Schematic of the differences in solvent

penetration

Filter paper Microfibrillated cellulose

Initially

Solvent penetra-

tion

Final compo-

site

(29)

Future Trends in Packaging Materials Parameter interaction

DISSOLUTION TIME LEVEL OF

DEFIBRILLATION

DEGREE OF

POLYMERIZA- TION

AMOUNT OF MATRIX

&

CONSOLIDATION

CRYSTAL- LINITY

HOMO- GENEOUS

OR

SANDWICH STRUCTURE

MECHANICAL PROPERTIES

(30)

Future Trends in Packaging Materials Conclusions

• Filter paper:

– Impressive increase in strength, stiffness and strain at break

– CrI losses

– Excellent consolidation.

• MFC:

– Moderate increase in strength and stiffness – Highest mechanical properties

– Limited solvent penetration due to tight interfibrillar network and high solvent viscosity.

– High crystallinity.

• [C

₄

mim]Cl:

– Depolymerized the cellulose

– Could be recycled by evaporation and re-used.

(31)

Future Trends in Packaging Materials Acknowledgments & references

The authors would like to thank the KEMPE Foundations, Örnsköldsvik, Sweden for the financial support of this work. We would also like to thank Mikael Niemistö for the

viscosity measurements.

Asi, O., 2008. Mechanical properties of glass-fiber reinforced epoxy composites filled with Al2O3 particles.

Journal of reinforced plastics and composites. Doi: 10.1177/0731684408093975.

Cai, J., Liu, Y. & Zhang, L., 2006. Dilute solution properties of cellulose in LiOH/urea aqueous system.

Journal of polymer science part b polymer physics, 44(21), 3093.

Duchemin, B.J.C., Newman, R.H. & Staiger, M.P., 2009. Structure-property relationship of all-cellulose composites. Composites Science and Technology, In Press, Accepted Manuscript. Available at:

http://www.sciencedirect.com/science/article/B6TWT-4VSB1D9-2/2/d5f3b8553b778c6c26a9d4ea8ec94543.

Fink, H.-P., et al., 2001. Structure formation of regenerated cellulose materials from NMMO-solutions.

Progress in Polymer Science, 26(9), 1473-1524.

Gindl, W. & Keckes, J., 2005. All-cellulose nanocomposite. Polymer, 46(23), 10221-10225.

Gindl, W., Martinschitz, K. J., Boesecke, P. & Keckes J., 2006. Changes in the Molecular Orientation and Tensile Properties of Uniaxially Drawn Cellulose Films, Biomacromolecules , 7 (11), 3146-3150.

Glasser, W.G. et al., 1999. Fiber-reinforced cellulosic thermoplastic composites. Journal of Applied Polymer Science, 73(7), 1329-1340.

Henriksson, M., et al., 2008. Cellulose Nanopaper Structures of High Toughness. Biomacromolecules, 9(6), 1579-1585.

Iwamoto, S., Nano-fibrillation of pulp fibers for the processing of transparent nanocomposites. Applied physics. A, Materials science & processing, 2007. 89(2), 461.

Ishikawa, A., Okano, T. & Sugiyama, J., 1997. Fine structure and tensile properties of ramie fibres in the crystalline form of cellulose I, II, IIII and IVI. Polymer, 38(2), 463-468.

Liu, S., et al., 2009. Supramolecular Structure and Properties of High Strength Regenerated Cellulose Films. Macromolecular Bioscience, 9(1), 29-35.

Nakagaito, A.N., et al., 2004. The effect of morphological changes from pulp fiber towards nano-scale fibrillated cellulose on the mechanical properties of high-strength plant fiber based composites. Applied physics. A, Materials science & processing. 78(4), 547.

Nakagaito, A.N., 2005. Novel high-strength biocomposites based on microfibrillated cellulose having nano- order-unit web-like network structure. Applied physics. B, Lasers and optics, 80(1), 155.

Nakagaito, A.N. and H. Yano, 2008. The effect of fiber content on the mechanical and thermal expansion properties of biocomposites based on microfibrillated cellulose. Cellulose. 15(4), 555-559.

Nishino, T., Matsuda, I. & Hirao, K., 2004. All-cellulose composite. Macromolecules, 37(20), 7683-7687.

Nishino, T., Takano, K. & Nakamae, K., 1995. Elastic Modulus of the Crystalline Regions of Cellulose Polymorphs. Journal of Polymer Science: Part B: Polymer Physics, 33(11), 1647-1651.

Nishino, T. & Arimoto, N., 2007. All-Cellulose Composite Prepared by Selective Dissolving of Fiber Surface.

Biomacromolecules, 8(9), 2712-2716.

Oksman, K., Skrifvars, M. & Selin, J.-., 2003. Natural fibres as reinforcement in polylactic acid (PLA) composites. Composites Science and Technology, 63(9), 1317-1324.

Segal, L. et al., 1959. An empirical method for estimating the degree of crystallinity of native cellulose using the X-ray diffractometer. Textile Res. J., 29(10), 786-794.

Soykeabkaew, N. et al., 2008. All-cellulose composites by surface selective dissolution of aligned ligno- cellulosic fibres. Composites Science and Technology, 68(10-11), 2201-2207.

Soykeabkaew, N., Nishino, T. & Peijs, T., 2009. All-Cellulose Composites of Regenerated Cellulose Fibres by Surface Selective Dissolution. Composites Part A: Applied Science and Manufacturing, In Press, Accepted Manuscript. Available at:

http://www.sciencedirect.com/science/article/B6TWN-4TY496H-1/2/bc9e6cce8cd73b0d1bd844bf0db63202.

Soykeabkaew, N., Sian, C., Gea S., Nishino, T. & Peijs T., 2009. All-cellulose nanocomposites by surface dissolution of bacterial cellulose. Cellulose, DOI 10.1007/s10570-009-9285-1.

Wambua, P., Ivens, J. & Verpoest, I., 2003. Natural fibres: can they replace glass in fibre reinforced plastics? Composites Science and Technology, 63(9), 1259-1264.

Zhao, Q. et al., 2009. Novel all-cellulose ecocomposites prepared in ionic liquids. Cellulose.

(32)

Future Trends in Packaging Materials

The greenness of all-cellulose composites...

...is determined by the choice of solvent.



LiCl/DMAc: has been used so far for most all-cellulose composites, but...



NMMO: is considered as being the greenest solvent industrially. However...



Low temperatures solvents NaOH, NaOH/urea, LiOH...



Strong acids



Ionic liquid: not perfect (yet) but already very advantageous

FACTORS: EFFICIENCY; PRICE; AVAILABILITY; RECYCLABILITY; TOXICItY; PRESENCE OF V.O.C.; OTHER HAZARDOUS ASPECTS; EASINESS OF USE (WORKING TEMPERATURE, VISCOSITY, HYGROSCOPICITY)...