GREEN NANOCELLULOSIC BARRIERS

Yulin Deng

Art Ragauskas

Georgia Institute of Technology

April 2012

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Barrier Packaging

• Barrier Packaging

– Serves as Barrier to: • Air

• Water

• Grease

• Microbes

• Odor

• Common Materials – Glass

– Metals

– Petroleum Based Plastics

– Wax/Plastic Coated Paper Cartons

Green Packaging

•Non Toxic/Chemically Inert

•Recyclable, Sustainable

•Stable

Non

Toxic/Chemically

Inert

Recyclable,

Sustainable

Stable

• Used for packaging – Food

– Pharmaceutical Products

– Cosmetics

– Dry goods

• Global Packaging Market – Valued at $3.8 Billion in 2007

– Projected to grow to $4.6 Billion by 2014

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• Plastics

– Petroleum Based

– Not sustainable

– End of life disposal challenges

• Metals

– Aluminum – Not chemically inert, Expensive

– Tin – Heavy, Unsustainable, Expensive

• Glass

– Adds to weight and transport expenses

– Fragile

Paper packaging

Paper packaging non-paper packaging

Paper Packaging has the most favorable

properties

Sustainable

Lightweight

Low Cost

Easily transported and stored

However, pure cellulose paper does not

have barrier properties so it is usually

coated by

Plastic

Wax

Aluminum

These coating materials limit recyclability

of the packaging

Non-paper packaging

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Nano cellulosic fibers

• Cellulose fibers of nano scale (Diameter 10-50nm, Length ~1000nm).

• Renewable

• Biodegradable

• Low density packaging – reduction in weight therefore transportation costs

• Can be cast into dense coating films because of their small size and strong hydrogen bonding characteristics

• Easily being chemically modified

• Widely used for nanocomposite applications

J. Lee, Y. Deng, The Morphology and Mechanism

Properties of Ice-Templated Cellulose Microfibril

Porous Foams, Soft Matter, (2011) 7, 6034

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Preparation of cellulosic nanofibers

• Produced by the various methods

– Mechanical homogenization

• Energy Intensive 72-108 GJ/Ton

• High energy costs

– Chemical pretreatment of cellulose with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)

• TEMPO is expensive and toxic

– Enzyme pretreatment followed by mechanical homogenization

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Objectives

• Develop a energy saving method using enzyme pretreatment followed by mechanical homogenization for cellulose nanofibril preparation

• Our research team will develop several new nanomaterials, including functionalized cellulose whiskers or nanofibrils with chemically modified xylan coatings for coating.

• A thin, but very dense layer of hydrophobically modified NCC/xylan will be applied to paper coating to improve water and air barrier

• Inorganic near-nano sized platy clay particles, available from IMERYS, will be assembled into the modified cellulose/xylan based nanocoating layer.

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Our approaches: Nanostructure coating

Coating layer: Nanofibrils or xylan coating layer: good: dense and high resistance to

air and vapor • Can be further modified to increase the hydrophobicity so the water resistance

• Inorganic nanoclay can be added to the cellulose nanofibrils dense layer to improve air, water

and oil resistance

Dense coating layer of

cellulose nanofibrils: Low

gas gas permittance

Porous paper

Adding high aspect ration clay,

modify nanocellulose to further

reduce the gas permibility

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Develop both gas and liquid water/grease barriers

Bottom layer: Paper with

large pores: Poor barrier for

air, water and oil

Middle layer: Nanofibrils or

Zylan coating layer: good:

dense and high resistance to

air and vapor • Can be further modified to

increase the hydrophobicity

so the water resistance

• Inorganic nanoclay can be

added to the cellulose

nanofibrils dense layer to

improve air, water and oil

resistance

Top layer: Nanostructured

roughness for

Superhydrophobic/

superlyophobic

Addition of top hydrophobic

layer to protect barrier layer

underneath.

Hydrophobic layer also helps

with keeping the surface clean

due to self cleaning

properties.

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Approaches

• Film Forming Hydrophobic Hemicelluloses: Although, the use of NCC with xylan decreases water transmission of xylan films, for board applications we will need to extend this effect by a +3 fold order of magnitude on the surface of paper board.

• Convert NCC to a hydrophobic Structure: The nano-fibrillated cellulose offer the opportunity to prepare dense coatings for packaging board. Further modification can convert it from hydrophilic to hydrophobic or lyophobic to achieve high water, vapor and air resistance

• Further improve water and air resistance using plated kaolin clay/cellulose nanomaterials: Imery’s plated clay will be used to further improve the barrier of water and air of nano cellulose or xylan

• Optimization of surface nanostructure for superhydrophobic: beside to low water and air permeance, but also surperhydrophobic paper will be fabricated using cellulose nanofibrils

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• Preparation

Bleached kraft pulp

H2SO4 or HCl

Birch xylan composite films were formed by adding an

aqueous suspension neutral or sulphonated whisker

suspension to xylan

0.0, 5.0, 10.0, 16.0, 25.0, 50.0 wt% of the total mixture of

xylan, whisker and sorbitol

Solution cast

Prior: Xylan Cellulosics Films

AFM of Cellulose

Nanowiskers

Birefringence of

Cellulose Nanowiskers

TEM of Cellulose Nanowiskers1

AFM of Cellulose

Nanowiskers

Birefringence of

Cellulose Nanowiskers

TEM of Cellulose Nanowiskers1

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SEM Images of Films

50 nm

(B)

SEM surface images of the (A) control xylan, (B) xylan reinforced with

sulfonated whisker

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SEM Images of Films

50 nm

(B)

SEM facture images of the (A) control xylan, (B) xylan reinforced with

sulfonated whisker

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Effect of Whiskers on Tensile Strength of Xylan Films

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Effect of Sulfonated Whisker Specific Water Vapor Transmission Rate of Xylan Films

0

0.05

0.1

0.15

0.2

0.25

0 2 4 6 8 10 12 14 16

time (h)

weig

ht d

ifferen

ce (g

)/h

Control, Xylan

xylan reinforced w ith 10% sulfonated

w hisker

Xylan reinforced w ith 50% hydrochloride

w hisker

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Effect of Cellulose Whiskers Dosage on O2 Transmission of Xylan Films.

O2 Transmission of Xylan Films.

Our previous results Nanocellulose-Xylan

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Our previous results

SEM of poly(allylamine hydrochloride)-

kaolin clay on a softwood kraft fiber.

Polymer Clay Self-Assembly Complexes on Paper

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Our previous results Polymer Clay Self-Assembly Complexes on Paper

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Interesting results from literature (Cellulose nanofibrils coating)

• Barrier and Mechanical properties affected by moisture content

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Interesting results from literature (Cellulose nanofibrils coating)

• Water adsorption increases with increase in humidity.

• Tensile strength of films decreases significantly with increase in humidity.

Christian Aulin, Mikael Gallstedt, Tom Lindstrom, Cellulose (2010) 17:559–574

It can be seen that the nanocellulose coating has very high barrier for air transfer at low

relative humidity. However, the permeance decreases dramatically. We need to use

mordified nanofibrils to reduce the vapor response.

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Interesting results from literature (Cellulose nanofibrils coating)

• Water adsorption increases with increase in humidity.

• Tensile strength of films decreases significantly with increase in humidity.

Christian Aulin, Mikael Gallstedt, Tom Lindstrom, Cellulose (2010) 17:559–574

It can be seen that the nanocellulose coating has very high barrier for air transfer at low

relative humidity. However, the permeance decreases dramatically. We need to use

modified nanofibrils to reduce the vapor response.

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Methods to Improve Properties

• Chemical and physical modification of Cellulose Nano fibers and control the surface morphology

• Superhydrophobic surface can be achieved by polymethylsilsesquioxane modification of cellulose fibers

S. Li; S. Zhang; X. Wang, Fabrication of Superhydrophobic Cellulose-Based Materials through a Solution-

Immersion Process, Langmuir, (2008) 24, 5585-5590

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Our recent results: Vapor Deposition of POTS

• Increases hydrophobic behavior of surface.

• A)- untreated

• B) Hydrophobic with POTS treatment

• C)- Super hydrophobic with nano particles

and POTS treatment

POTS: 1H,1H,2H,2H-perfluoro-octyltriethoxysilane

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Surface Morphology

• Change in surface morphology – addition of inorganic/organic nanoparticles to fiber surface.

Stanssens, D., H. Van den Abbeele, et al. (2011). "Creating water-repellent and super-hydrophobic

cellulose substrates by deposition of organic nanoparticles." Materials Letters 65(12): 1781-1784.

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Summary

• Both literature and our previous results indicate that cellulose or xylan nanomaterials can be used to coat on paper surface to form a dense coating layer which will remarkably reduce the gas and vapor permeability.

• The gas and vapor resistance can be further improved by chemical modification of cellulosic materials.

• The composite of clay and cellulosic nanomaterials for coating has not been done before, and it is expected that this method can further increase the gas barrier.

• The nanoroughness on the top layer of the coating can be achieved with cellulose nanofibrils coating. The coating layer

could be alternated to superhydrophobic and self-cleaning surface

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GT/Partner Nanocellulose Facilities