the effect of nano-fibrillated cellulose on the … effect of nano-fibrillated cellulose on the...

The effect of Nano-fibrillated cellulose on the mechanical properties of polymer films.

Gerard Gagnon, Rikard Rigdal, Jake Schual-Berke, Mike Bilodeau and Douglas W. Bousfield

Department of Chemical and Biological Engineering and the Process Development Center University of Maine

Orono, ME 04469 USA EXTENDED ABSTRACT Nano-fibrillated cellulose (NFC) was produced mechanically from a bleached soft wood kraft fiber using a pre-treatment method followed by refining or homogenization. Field emission scanning electron microscope images of the material reveals a large number of fine scale fibers with diameters between 20-50 nm and lengths of over a micron. Polymer films were produced by mixing NFC with a styrene-butadiene latex or polyvinyl alcohol. Films were cast onto Teflon coated aluminum foil and dried under heat lamps. A mechanical tester characterized the elastic modulus of the films, the ultimate tensile strengths, and the rupture strains. Figure 1 compares the stress strain results of the pure latex film with the film that contains 18% by weight NFC. The pure latex has a large region of regular stretching and a high rupture strain. The addition of NFC increases the elastic modulus, decreases the rupture strain and has little effect on the ultimate tensile strength. Similar results are seen for the polyvinyl alcohol films. Figures 2 and 3 show the Young’s modulus for the latex and polyvinyl alcohol films, respectively. The yield point increased for latex films with increasing amounts of NFC while no trend was observed for polyvinyl alcohol films.The influence of citric acid addition on these films is also reported. There is significant scatter in the data as can be seen in the repeat results and the error bars.

Figure 1. Results of pure latex film (left) and a film with 18% NFC by weight (right). Different curves are for different samples but of the same composition.

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NFC loading level Figure 3. Young’s modulus for polyvinyl alcohol films with various levels of NFC. While the addition of NFC to these polymers did increase the modulus, the strain to failure decreased. This can be seen in Fig.1 and noting the different ranges for the x axis. NFC clearly makes a stiffer material. The ultimate tensile strength is not a strong function of NFC content. The NFC used in this study has a wide particle size distribution. Therefore, even a few large particles could misrepresent the content of nano-scale material. In addition, larger material may give rise to weak points within the structure. However, NFC is clearly shown here to have the ability to produce a more rigid polymer film.

The Effect of Nano-Fibrillated Cellulose on the Mechanical Properties of Polymer Films

Gerard R. Gagnon Jr., Rikard Rigdal, Jake Schual-Berke, Michael Bilodeau and

Douglas W. BousfieldDepartment of Chemical and Biological Engineering

University of Maine

1 Adv Polym Sci 205 (2006) 49-96, 2 Materials Science and Engineering A 490 (2008) 131–137,

Introduction• Nano-fibrillated cellulose (NFC) may be used for

• medical devices• reinforcing agent in plastic composites• food additive• paper & coatings• cosmetic products• dispersions & emulsions.1,2

• NFCs as a reinforcing agent in composites can• increase strength• lower material cost

• NFCs are compatible with water-based polymer systems, such as styrene-butadiene (SBR) latex and polyvinyl alcohol (PVOH)

2Tappi Nanotechnology September 28-30, 2010

Materials Used for ProducingNanofiber Reinforced Polymer Films

• Nanofibers were produced by mechanical treatment of cellulose fibers, with and without a chemical pre-treatment.

• The chemical pre-treatment of NFC consisted of partially hydrolyzing the fiber with MgCl2 and heat.

• SBR latex films with chemically pre-treated NFC were produced.

• Polyvinyl alcohol (PVOH) films with and without chemically pre-treated NFC were produced.

Tappi Nanotechnology September 28-30, 2010 3

Materials Used for ProducingNanofiber Reinforced Polymer Films

• SBR latex• Tg of 10oC• Particle size 150 nm

• PVOH• molecular weight - 85,000 to 124,000 g/mol • >99% hydrolyzed


Materials Used for Producing NFC Reinforced Polymer Films


FE SEM image ofchemically pre-treated nanofibrillar cellulose

• A draw down method was developed to prepare SBR latex/NFC composites

• Wire wound rod used to form wet film.

• Film dried under heat lamps to avoid cracking and trapping air.

• Samples of films cut between two sheet of paper at an elevated temperature to avoid cracking.

• Films of PVOH were prepared by drying aqueous mixtures of PVOH/NFC in a thin open mold of Mylar sheets under a heat lamp.

Method of Preparing Latex / NFC Films

Wire Wound Coating Rod

Teflon Coated Aluminium Foil

Coating Direction

9 ml of Liquid

Rikard Rigdal 2008


Tensile Testing

• Rectangular samples were cut from each film parallel to the draw down direction.

• Tensile tests were performed using a standard laboratory tensile tester. Averages are from at least 6 samples per condition.

Rikard Rigdal 2008


SBR Latex & NFC Films: Tensile Testing Results

• NFC film demonstrated a linear elastic region up to the rupture strain.

• The elastic modulus of NFC film is significantly higher than for the pure SBR latex film.

Rikard Rigdal 2008


Static Tensile Test – NFC Static Tensile Test – SBR only

Mechanical Properties of SBR Latex Films Containing Chemically Pre-treated NFC

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NFC Loading Level• The Young’s Modulus increased for the two highest addition levels

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Mechanical Properties of SBR Latex Films Containing Chemically Pre-treated NFC

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• The addition of pre-treated NFC to SBR latex films did not significantly impact the ultimate tensile strength.

• Rupture stress decreases with increasing NFC concentration. The composites were becoming increasingly more brittle.

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Mechanical Properties of PVOH Films Containing Untreated NFC

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• Young’s modulus of PVOH films increased at the highest loading of NFC.


• NFC loading did not significantly impact the ultimate tensile strength.• The two highest loadings of NFC resulted in more brittle PVOH films,

requiring much less strain to break.

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Mechanical Properties of PVOH Films Containing Untreated NFC


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• Young’s Modulus showed a modest increase at the higher pre-treated NFC concentrations.

Mechanical Properties of PVOH Films Containing Chemically Pre-treated NFC


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• Adding chemically pre-treated NFC to PVOH films did not significantly improve the ultimate tensile strength.

Mechanical Properties of PVOH Films Containing Chemically Pre-treated NFC


• SBR latex, kaolin and pretreated NFC films had higher tensile strength and Young’s Modulus than SBR latex and kaolin films.

Rikard Rigdal 2008


SBR Latex / Kaolin / NFC Films: Mechanical Properties

SBR & kaolin (50/50)

+ 2 wt% NFC

+ 5 wt% NFC

• For SBR latex composite films, increasing NFC content

• increased Young’s Modulus• no significant impact on the ultimate tensile strength• decreased the rupture strain.

Summary


• For PVOH composite films, increasing NFC content

• increased Young’s Modulus• no significant impact on the ultimate tensile strength• decreased the rupture strain.

• Chemically pre-treating NFC showed no significant impact on reinforcement properties compared to untreated NFC.

Summary


• For SBR latex & kaolin composite films, increasing NFC content

• increased Young’s Modulus• increased ultimate tensile strength• decreased the rupture strain.

Summary


Questions


the effect of nano-fibrillated cellulose on the … effect of nano-fibrillated cellulose on the...

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