Post on 25-Feb-2016
description
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 compositePolymeric 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)