from paper to nanopaper: evolution of mechanical …€¦ · sehaqui et al. biomacromolecules, 2011...

NANOCELULOSA: PRODUCCIÓN, CARACTERIZACIÓN Y SU POTENCIAL EN LA FABRICACIÓN DE PAPEL Y NANOPAPEL

Formación continuada

FROM PAPER TO NANOPAPER: EVOLUTION OF MECHANICAL AND

PHYSICAL PROPERTIES

Madrid, 15th – 16th October

ONGOING MODIFICATION OF CELLULOSE NANOFIBERS AND THEIR POTENTIAL APPLICATIONS

Fabiola Vilaseca

Cellulose (2014) 21:2599–2609

I. Gonzalez • M. Alcala • G. Chinga-Carrasco • F. Vilaseca • S. Boufi • P. Mutje

Contenido de la sesión Introduction to Nanopapaer

What is Nanopaper? Current studies on nanopaper

Fabrication of Nanopapers Dispersion of nanofibres Sheet formation Drying

Characterization of Nanopapers Physical properties

• Thickness • Density and Bulk • Opacity • Porosity

Mechanical properties • Tensile strength • Tensile index and breaking length • Young’s modulus • Strain • Effect of mechanical treatment intensity on nanopaper’s properties

What is Nanopaper ?

The term refers to papers with a 51 wt% content or more of cellulose nanofibres.

Nanopapers can be fabricated and characterized at laboratory level using techniques similar to those used for normal papers.

Sehaqui et al. Biomacromolecules, 2010

Remarkable works on nanopapers • Henriksson et al. 2008. Nanopapers fabricated from CNF with different polymerization degree (DP).

Henriksson et al. Biomacromolecules, 2008 a- Microphotography (FE-SEM) of nanopaper. b- Microphotography (FE-SEM) of failure point in a mechanically tested nanopaper sample.

Remarkable works on nanopapers Olsson et al. 2010. Nanopapers with magnetic properties.

Olsson et al. Nature nanotechnology, 2010

Remarkable works on nanopapers Sehaqui et al. 2010. Fast method for preparation of nanopapers


Remarkable works on nanopapers Sehaqui et al. 2011. Highly porous nanopapers.

Sehaqui et al. Biomacromolecules, 2011 a- NFC gel b- transparent nanopaper sample. c- Highly porous nanopaper

Remarkable works on nanopapers Youssef et al. 2013. Properties comparison among nanopapers fabricated from rapeseed fibres and bacterial cellulose.

Youssef et al. Industrial Crops and Products, 2013

Nanopaper fabrication

Nanopaper fabrication 1. Dispersion of CNF in water with a pulp disintegrator at 180000 revolutions. This is an important stage which defines many of the nanopaper’s final properties.


2. Nanopaper is formed in a Rapid-Köthen like equipment assisted with a vacuum pump that generates -0,35 bars of negative pressure.


3. A 0.65 μm porous diameter nitrocellulose membrane is laid at the bottom of the stock container in order to retain the nanofibres during the filtering process.

Fabricación del nanopapel

4. Filtering takes between 3 and 4 hours. At the end of this time a transparent, wet nanofibre cake is obtained. This cake is carefully peeled off the nitrocellulose membrane and put between two absorbing papers.


5. Next, nanopaper is vacuum dried at 90ºC during 15-20 minutes depending on the moisture content of the wet cake.


6. Once dried, the nanopaper is weighted and conditioned in a climate chamber.

Nanopaper characterization Physical properties: evolution of physical properties from ordinary paper to 100% nanopaper and their different grades.

Sample Thickness

(μm)

Density

(gr/cm3)

Bulk

(cm3/gr)

Opacity

(%)

Porosity

Gurley

(s)

Porosity

(%)

100%Fibres 101 0,640 1,562 84,50 2,00 57,30

75%fibres/25%NFC 88 0,730 1,569 51,02 1912 51,30

50%fibres/50%NFC 75 0,810 1,233 45,66 4284 46.00

25%fibres/75%NFC 62 0,950 1,051 40,20 <5000 36,66

100%NFC 52 1,200 0,832 33,20 <5000 20,00

Nanopaper characterization Thickness: Its accurate determination is decisive in order to calculate other nanopaper’s properties such as density and tensile strength.

The technique used to determine thickness can vary significantly the result.

Chinga-Carrasco & Syverud, J Nanopart Res, 2009 Chinga-Carrasco et al. Microsc. Microanal., 2011

Thickness: It is reduced when the NFC content increases.

Nanopaper characterization Opacity: It is the amount of light scattered by paper. It is measured by equipments that detect the scattered light, such as the ERIC.

Nanopaper characterization Porosity: The increase in the NFC amount makes paper more robust and compact and thus less porous.

SEM microphotography of: a- ordinary paper with 100% bleached ecualyptus polp. b- 50 % fibres 50% NFC c- nanopaper 100 % NFC

a b c

Nanopaper characterization SEM microphotography: The images show the structure of nanopapers with 100% NFC content.

Nanopaper characterization Mechanical properties: evolution of strength from paper to nanopaper.

σ (Mpa)= tensile strength E (GPa)= Young’s modulus

ε (%) = strain

Nanopaper characterization Mechanical properties: evolution of strength from paper to nanopaper.

Samples σ

(MPa)

T.I.

(N·m/gr)

E

(GPa)

ε

(%)

Breaking L.

(m)

100%Fibres 41,20 25,5 2,85 0,65 2601

75%fibres/25%NFC 80,50 55,8 6,90 3,23 5691

50%fibres/50%NFC 91,80 64,5 8,2 3,57 6579

25%fibres/75%NFC 113,50 81,15 10,90 1,90 8277

100%NFC 132,60 95,85 11,90 2,55 9776

σ (Mpa)= tensile strength E (GPa)= Young’s modulus

ε (%) = strain T.I. (N·m/gr)= Tensile Index

Breaking L.= Breaking length

Nanopaper characterization Tensile strength: The results obtained in the present work correspond to those reported by other authors for nanopapers with similar degree of polymerization.

Muestra σ

(MPa) 100%Fibras 41,20

75%fibras/25%NFC 80,50

50%fibras/50%NFC 91,80

25%fibras/75%NFC 113,50

100%NFC 132,60

Henriksson et al. Biomacromolecules, 2008


DP : 423 -COOH content: 0,4mmol/g

Nanopaper characterization Young’s modulus: comparison of Young’s modulus results obtained in the present work and others reported in the literature.

Sample E

(GPa)

100%Fibres 2,85

75%fibres/25%NFC 6,90



100%NFC 11,90



Nanopaper characterization Strain to failure: Defines the percentage of elongation before mechanical failure.

Sample ε

(%)

100%Fibres 0,65




100%NFC 2,55



Nanopaper characterization Mechanical properties: Effect of the number of passes of NFC through a high pressure homogenizer on the mechanical properties of nanopaper.

Sample

(nº of passes and pressure in bars)

σ

(MPa)

T.I.

(N·m/gr)

E

(GPa)

ε

(%)

Breaking length

(m) 5 (300) 74,65 49,62 7,45 2,02 5061

10 (5-300+5-600) 100,36 69,40 10,13 2,00 7078

15 (5-300+10-600) 125,00 88,35 11,00 2,32 9011

20 (5-300+15-600) 132,60 95,85 11,90 2,55 9776

Tensile strength: the number of passes through the homogenizer influences the degree of delamination in NFC which determines also the strength of nanopaper.

Nanopaper characterization Tensile strength: the number of passes through the homogenizer influences the degree of delamination in NFC which determines also the strength of nanopaper.

Nanopaper characterization Young’s modulus: more passes of NFC through the homogenizer also increases nanopaper’s stiffness.

Key aspects to remember A pulp slurry with CNF content higher than 51% was considered as nanopaper, and it can be obtained by similar experimental procedures than standard paper. From paper to nanopaper you will get: higher density but lower thickness, bulk, porosity, opacity and porosity. Alo tensile index, strength and stiffness will increase, although deformation / strain increases up to 50% of CNF, and then start decreasing. The number of passes through the homogenizer affects the microfibrillation process and so the mechanical properties of the ensued nanopaper.

From different article (Cellulose (2013) 20:2909-2921), the intrinsic properties of CNF were calculated to be:

7 GPa strength , 160 GPa stiff

Thank you very much for your attention!!

from paper to nanopaper: evolution of mechanical …€¦ · sehaqui et al. biomacromolecules, 2011...

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