Cellulose- and Chitin-Based Coatings and Films

Carson MeredithProfessor

Chemical & Biomolecular EngineeringGeorgia TechAtlanta, GA

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One Motivation - Packaging

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• 1.3 billion tons of food, 1/3 of the world’s production, is spoiled each year before it gets to a consumer’s table.

• 2012 food/beverage packaging market $276 billion

• 10% is flexible plastic• 27% is rigid plastic• Nearly all of these are petroleum-derived barrier

plastics

www.foodproductiondaily.com

Chem. Soc. Rev. 2011, 40, 5266-5281Chem. Soc. Rev. 2014, 43, 588-610

poly(ethylene terephthalate) (PET) poly(vinylidene chloride))

Motivation

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Other Motivations

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• Composites• Light-weight applications in transportation

sector• Futuris / American Process / Swinburne /

Forest Products Laboratory / Clark Atlanta University Collaboration

• Adhesives• Foams and porous materials

• Lightweighting• Insulative• Battery electrodes

FuturisAmericanProcess

GaTechCAUSwinburneUSDA-FPL

Cellulose in wood and plant structures

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Estimated cellulosenanocrystal

Like carbon fiber,potential for high-strengthbut light-weight

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Chitin

• 2nd most abundant polysaccharide

(1010-1011 tons each year)

• Structure similar to cellulose

• Ability to be functionalized

• Biocompatible

• Remarkable affinity to proteins

• Renewable

Kohr E. Chitin: fulfilling a biomaterials promise. Elsevier Science, 20017

Chitin

Hierarchical architecture in nature

• Lobster exoskeleton: chitin and proteins assemble into hierarchical structures• Exoskeleton consists of chitin nanofibers

Lobsterexoskeleton

Acta Materialia 2005, 53: 4281 8

Bio-derived gas barrier materials

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P =

Q = vol / time

A = area h

Δp = pressure change

P = DS

QhAΔp

1 Barrer = [10−11 cm3 cm cm−2 s−1 mmHg−1]

Key figure ispermeability, P

Units: [cm3 µm m−2 d−1 kPa−1]

Bio-derived gas barrier materials

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High aspect-ratio composites used to increase diffusion path length

Barrier P difficult to achieve defects at interfaces dispersion of filler

Recyclability impacted

Chitin and Cellulose nanofibers offer an advantage if used in neat form.

Bio-derived gas barrier materials

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Nair , Zhu, Deng, RagauskasSustainable Chemical Processes 2014

Cellulose nanofibers show promise as barrier films

Sharma et al., RSC Advances 2014(Group of Prof. Yulin Deng)

PO2 = 0.01 cc um / m2 d kPa

PO2 = 0.17 cc um / m2 d kPaUntreated CNF

175 °C Treated CNF

Bio-derived gas barrier materials

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Only a few reports of barrier films involving chitin:

• Regenerated chitin films plasticized with glycerolPO2 = 0.003 barrer (35 °C)

• Composite of chitin nanowhiskers coated on PLA PO2 = 0.001 barrer

• No pure chitin films with high barrier properties (prior to our work)

International Journal of Biological Macromolecules 2012, 50, 69

Journal of Materials Chemistry A 2013, 1 1867

Challenges for both cellulose and chitin in applications

• InsolubilityOrganic Solvents

Atalla, R. H. and Isogai, A., in Polysaccharides : structural diversityand functional versatility, 2005 13

Challenges for both cellulose and chitin in applications• Insolubility

• Approaches to process cellulose / chitinRegeneration: dissolution followed by precipitation

• strong acids, bases or volatile organic solvents• disrupts intrinsically high crystallinity

Extraction and dispersion of nano-fibers Follow by assembly into film during drying

• Acid hydrolysis• Peroxide oxidation (TEMPO)• Grinding result in gelling suspensions• Ultrasonication cannot extract most crystalline α form• High-pressure homogenization Our approach

Chitin nanofibers (ChNFs): Wu and Meredith Biomacromolecules 2014, 15, 4614

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Chitin Nanofiber Generation

Crab shell

Chitin purification:deproteination and dimineralization

Purified chitin/water

Chitin nanofiber/water

dispersion

Mechanical shearing

Chitin nanofiber (20 nm)(pH 4)

Zeta potential curve of chitin nanofiber

Purified chitin (micro-size particles)

0.5 wt.% of chitin

Wu and Meredith Biomacromolecules 2014, 15, 4614 15

13C CP-MAS solid state NMR of purified chitin from crab shells

Degree of acetylation = 92.4%

Wu and Meredith Biomacromolecules 2014, 15, 4614 16

Morphology of Chitin

Beforehomogenizer

Afterhomogenizer(35 passes)

pH 4.1 pH 7.0

Wu and Meredith Biomacromolecules 2014, 15, 4614 17

Rheological Properties of DispersionsChNF/water

pH of 4.135 passes in homogenizer

ChNF/water pH of 4.1

4 passes in homogenizer

Wu and Meredith Biomacromolecules 2014, 15, 4614 18

Films from Chitin Nanofibers

Wu and Meredith Biomacromolecules 2014, 15, 461419

Mechanical Properties

ACS Appl. Mater. Interfaces 2013, 5, 4640−4647

Chitin nanofiber (ChNF) Film Cellulose (CNC) Film

Biomacromolecules 2014, 15, 4614

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Gas Kinetic

diameter (Å)

Permeability

(barrer)

H2 2.89 0.024

CO2 3.30 0.018

O2 3.46 0.006

N2 3.64 0.0034

CH4 3.80 0.0027

Gas permeabilities in ChNF films

0% relative humidityWu and Meredith Biomacromolecules 2014, 15, 4614 21

PO2 (barrer) PCO2 (barrer)PE 0.75-4.73 11.7-14.6PP 0.75-1.52, 4PET 0.015-0.076 0.3ChNF 0.006 0.018EVOH 1.5x10-5

CNF 1x10-7

0 % RH

Duan et al. Journal of Materials Chemistry A 2013, 1, 1867Gholizadeh et al. Mater. Des. 2007, 28, 2528Jarus et al. Polymer 2002, 43, 2401Tsai et al. Adv. Mater. 2005, 17, 1769

ChNF Compared to Other Films

Wu and Meredith Biomacromolecules 2014, 15, 4614 22

Chitin-based porous materials

Can we mimic and improve upon this intricate natural structure?

1 µm1 mm

(a) (b) (c)

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Freeze drying: freezing rate effect • Starting materials: chitin nanofiber (20nm)/water dispersion

• Processing approach:

Step 1. freeze this dispersion at different conditions: liquid nitrogen, -80 °C,

-20 °C, -20 °C (slow) (freezing rate: liquid nitrogen>-80 °C >-20 °C)

Step 2. sublimation of ice crystals by freeze drier

• Chitin nanofiber (20nm)/water dispersion: liquid nitrogen freezing(sample bottom touched the liquid nitrogen)

Pore size: 59.2±7.6 μm

Wu and Meredith, ACS Macro Letters, 2014, 3, 18524

Freeze drying: freezing rate effect

• Chitin nanofiber(20nm)/water dispersion: liquid nitrogen freezing

• Chitin nanofiber(20nm)/water dispersion: -80 OC freezing

Pore size: 96.2±12.0 μm

Pore size: 59.2±7.6 μm

Wu and Meredith, ACS Macro Letters, 2014, 3, 18525

Freeze drying: freezing rate effect

Enlarged top SEM image

• Chitin nanofiber(20nm)/water dispersion: -20 °C

Pore size: 3.2±0.4 μm

Wu and Meredith, ACS Macro Letters, 2014, 3, 18526

CompositesCNC-Filled Epoxy

with Meisha Shofner (MSE)

Xu, Girouard, Schueneman, Shofner, Meredith, Polymer, 2013 27

Conclusions

– CNFs and ChNFs extracted via chemical/mechanical processes

– Formed direct into neat CNF or ChNF films • Low permeability• High transparency • Good mechanical properties.

– Developed process for nanoporous chitin foams via freeze drying

– Useful for high-strength composites

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Acknowledgements• GT Renewable Bioproducts Institute• USDA (Greg Schueneman)• Jie Wu, former Ph.D. Student• Natalie Girouard, current Ph.D. Student• Michael Avidano, undergrad researcher• Meisha Shofner, MSE

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