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All-Cellulose Hierarchical Composites:

Using Bacterial Cellulose To Modify Sisal Fibres

Polymer & Composite Engineering (PaCE) GroupDepartment of Chemical Engineering

A. Abbott, J. Juntaro & A. Bismarck

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Outline

•Need for renewable materials•Composite philosophy•Innovative modification of natural

fibres•Cellulose matrix processing•Route towards green composites•Truly green hierarchical composites•Possible applications

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Driving Forces To Green...•Growing environmental awareness•Stringent EOL legislation in the EU•Limitation of landfill capacity•Landfills count over 40% of plastic

wastes•Endangering of wild life•Most plastics are not Biodegradable !

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Legislation & Materials•EU agreed on a sustainable politic•End-of-life Vehicle directive 2000/53/EC

‣ Legislation to encourage re-use, recycling and other forms of recovery of ELVs

•Landfill directive 1999/31/EC‣ Legislation to prevent or reduce negative effects

on the environment from land filling of waste

•WEEE directive 2002/96/EC‣ Legislation to tackle rapidly increasing waste

stream of EEE by recycling of EEE and limitation of wastes.

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The Green Future•Strong need for new and reliable materials

•Requirements:‣Be recyclable, re-usable and biodegradable‣Obtained from sustainable resources‣Yield properties comparable to common plastics‣Be produced at low cost‣Be resistant to weatheringA possible solution would be the use

of cellulose based composite materials!

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Composite Architecture (1)•Composite have at least 2 constituents•Fillers

‣ Different purposes: reinforcement, fire-retardant, colour, cost reduction, additives, etc...

‣ Different sizes: from mesoscale to nanoscale

•Polymer matrix‣ Aim: transfer load to fillers, hold and protect fillers‣ Type: thermosets, thermoplastics

•Interface‣ Impact on composite properties

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Composite Architecture (2)•Cross-section of randomly reinforced

biodegradable composite

Polymeric matrix

Interface Natural fibre

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Composite Philosophy

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Hierarchical Composites

N-N Dimethylacetamide (DMAc), Lithium Chloride (LiCl), Sodium hydroxide (NaOH)

Bacterial cellulose (BC)

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Green Fibre Modification (1)•Gluconobacter fermentation for 1

week‣ Strain BRP 2001(suitable for dynamic culture)

•Modification during cellulose production

Bioflow culture conditions: temp 37°C ; pH 5.5 ; agitation 700 rpm ; aeration 5 l/min ; carbon source fructose

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Green Fibre Modification (2)

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Green Fibre Modification (3)

Fibre extraction from organic mass in 0.1 M NaOH 80°C 20 min

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Modification & Fibre Properties•No significant mechanical properties

loss after grafting procedure

Fibre conditioned @ 20°C and 50% RH; test performed @ 1mm/min, gauge length 20mm

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Modification & Fibre Crystallinity•Overall crystallinity increase after BC grafting•Surface fibre modified by green grafting process

Crystallinity evaluated with Segal’s equation

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Cellulose Matrix Processing•Matrix system obtained from MCC

‣ Properties tailoring f(processing time)‣ Brittle to ductile type behaviour

•Short fibres incorporation after suitable dissolution time

Dissolution mechanism presented by MacCormick (1979)

N-N Dimethylacetamide (DMAc), Lithium Chloride (LiCl)

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Matrix Crystallinity vs. Processing

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Matrix Toughness vs. Processing

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All-Cellulose Composites Prop.(1)

Testing Standards ISO 527-2 @ 1mm/min

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All-Cellulose Composites Prop.(2)

Testing Standards ISO 527-2 @ 1mm/min

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All-Cellulose Composites Prop.(3)

Heating rate 5OC/min @ 1Hz in nitrogen atmosphere

Test configuration: single cantilever beam

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SEM All-Cellulose Composite

SEM micrograph post cryo-fracture

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SEM Hierarchical Composite

SEM micrograph post cryo-fracture

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SEM Hierarchical Composite

SEM micrograph post cryo-fracture

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Conclusion

•Effective fibre surface modification with BC•Grafted fibre bulk properties unchanged•Improved interfacial adhesion & stress

transfer•100% cellulose composite •Hierarchical composite structure•Principle transferable to other systems•Fibre functionalization by cellulose

chemistry

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Potential Applications

Adapted from book: Natural fibers, Biopolymer and Biocomposites; Mohanty (2006)

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Acknowledgements• Dr Sakis Mantalaris (Head of Biological Systems Engineering

Laboratory)

Thanks For Listening!

Any Questions ?

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Matrix & Thermal Degradation

Heating rate 5oC/min under nitrogen atmosphere

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Bacterial Synthesised Products(1)•Reinforcement: Bacterial Cellulose

(BC)‣ Highly crystalline, pure cellulose compound‣ Tayloring BC properties during fermentation

Czaja, et. al, Biomaterials 2006

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Bacterial Synthesised Products(2)•BC produced by Gluconobacter and others•Ribbon-shape fibrils 8-50 nm diameter•Chemically identical to plant cellulose

Jonas & farah 1998

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BC network & Bacteria

BC Production (2) Young’s modulus of single nanofibril:78 GPa (similar to glass fibres)(Guhasos et al.,2005)

89% Crystallinity(Czaja et al.,2004)