Functional and Green End-of-life Nanocomposites: Design, Processing and Characterisation

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering

Abstract

There is currently a timely opportunity to create dramatically improved green (renewable) and environmentally-friendly biodegradable materials for high volume, low load, and low cost. By manufacturing new bacterial cellulose reinforced bio-derived polymer nanocomposites, a new class of hierarchical composites with both much improved mechanical and environmental performance, as well as reduced through-life costs will be possible. The resulting product will be made completely from renewable resources, and will be totally biodegradable. We are expecting greatly improved materials for which three major applications are envisioned: fibre reinforced green nanocomposites for the automotive and construction industry and foamed nanocomposites as novel insulating materials for the packaging and construction industries.

Publications

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Description The first aspect of this project focused on the fabrication of novel green materials using nanocellulose as the building block. Bacterial cellulose (BC) was used as the nanocellulose predominantly for this work. BC is highly crystalline pure cellulose with an inherent fibre diameter in the nano-scale. A single BC nanofibre was found to possess a Young's modulus of 114 GPa. All these properties are highly favourable for using BC as a nanofiller/reinforcement in green nanocomposite materials.



The surface of BC was rendered hydrophobic by grafting organic acids with various aliphatic chain lengths. These surface-modified BC was used as nano-filler for poly(L-lactide) (PLLA). Direct wetting measurements showed that the BC nanofibre-PLLA interface was improved due to the hydrophobisation of BC with organic acids. This led to the production of BC reinforced PLLA nanocomposites with improved tensile properties. Nanocellulose can also be obtained by grinding of wood pulp, producing nanofibrillated cellulose (NFC). The surface and bulk properties of one type of NFC and BC were compared in this work. Furthermore, the reinforcing ability of NFC and BC was also studied and it was observed that there is no significant difference in the mechanical performance of NFC or BC reinforced nanocomposites.



A novel method based on slurry dipping to coat sisal fibres with BC was developed to modify the surface of natural fibres. This method can produce either (i) a densely BC coating layer or (ii) "hairy" BC coated sisal fibres. Randomly oriented short BC coated sisal fibre reinforced hierarchical composites were manufactured. It was found that hierarchical (nano)composites containing BC coated sisal fibres and BC dispersed in the matrix were required to produce composites with improved mechanical properties. This slurry dipping method was also extended to produce robust short sisal fibre preforms. By infusing this preform with a bio-based thermosetting resin followed by curing, green composites with significantly improved mechanical properties were produced. BC was also used as stabiliser and nano-filler for the production of macroporous polymers made by frothing of acrylated epoxidised soybean oil followed by microwave curing.

Traditionally, BC is produced at flask scale under static conditions, which generates 0.02 to 5.42 g/L. However, cost-efficient production at industrial scale requires the use of bioreactors. One of the major drawbacks encountered at bioreactor scale remains the poor yield obtained. The High-Aspect-Ratio Vessel (HARV) rotating wall bioreactor, which offers a low shear stress culture environment, was used to produce BC. Acetobacter xylinum ATCC 53582 was employed to synthesize BC in the HARV and in a flask under static or agitated culture conditions. The yield of dried BC was found to be three times higher in the HARV than in the flask cultures under agitated conditions, whereas it was the same between the HARV and the flask cultures under static conditions. IR, XRD and TGA results indicated that the HARV-produced BC exhibited higher crystallinity (94%) to the flask-grown BC (87% and 83% under static and agitated conditions, respectively). The Young's modulus, the tensile strength and the strain at failure of HARV-grown BC were found to increase roughly by 215 % and 115 % compared to those measured for flask-grown BC in agitation and in static conditions, respectively.



Moreover, we explored methods to modify bacterial cellulose in-situ during its production in static culture; this was achieved i) by additing water soluble polymers and ii) by the addition and non-ionic sugar based surfactants. However, only the addition of surfactants resulted in a significant modification of the cellulose surface but also bulk and mechanical properties.
Exploitation Route The work will be of fundamental interest to a range of industries from composite manufacturers, OEM and users, such as Visteon. Specific interest in promoting any arising technology may come from the automotive and construction industry. Farmers will benefit from the project in so far that new much improved properties of green composites might increase the use of bio-derived polymers, natural fibres and nanocellulose. Benefits to the consumer and wider society as a whole will depend on the outcome of the research but are likely to include, for example, lighter components that provide financial and environmental advantages through reduced material usage and enhanced fuel-efficiency in transport applications. These materials also have the scope to offer considerably reduced through-life costs which are currently being demanded by the end-users. Renishaw, a manufacturer of spectroscopic equipment will benefit through this grant via increased sales of their equipment. Since SJE began his research into monitoring cellulosic deformation using Raman spectroscopy a number of groups have now taken this up as a technique. The project will open up the field of truly green hierarchically reinforced nanocomposites and help to stimulate new research into other applications and materials systems which could form the basis of a continued research activity both in both participating centres, and our collaborators across the world. Broader Impact: Through this collaborative project we aim to increase the interaction between materials science and engineering with bioengineering as well as basic sciences, chemistry and physics. This project will allow researchers at the postdoctoral and PhD levels to work at the interface of interdisciplinary bioprocessing and 'green' materials research through participations of researchers from Manchester and Imperial. The research efforts will advance the UK within a global agenda to develop sustainable new materials from renewable resources. Success in the utilisation of 'green' polymers as new alternative 'sustainable' materials will satisfy EU legislation and regulations that encourage the use of renewable materials to reduce our dependence on petroleum. Use of nanotechnology in multifarious applications through fundamental research would broadly satisfy global nanotechnology initiative that would lead towards the next industrial revolution.
Sectors Creative Economy,Environment

URL http://www3.imperial.ac.uk/portal/page/portallive/polymersandcompositesengineering/aboutpace/greenmaterials
 
Description Nanocellulose reinforced polymer composites in the form of structural panels and porous polymer foams were developed. Hierarchical natural fibre-reinforced, nanocellulose-reinforced renewable polymer composites were created by depositing a nanocellulose coating around (natural) fibres to produce mechanically robust short natural fibre mats/preforms. These fibre preforms can be infused with a liquid monomer (resin), which can then cured to yield truly green natural fibre-reinforced, nanocellulose-reinforced hierarchical composites. This technology (process) and the resulting materials were patented. This research was highlighted at a three-day exhibition/workshop on nanocellulose in the Antenna Wing of the London Science Museum, which has attracted 10,000 visitors according to the Museum, and the first Imperial Festival.
First Year Of Impact 2013
Sector Environment,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

 
Description EPSRC/Imperial College London
Amount £47,736 (GBP)
Funding ID KTS 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 10/2011 
End 09/2012
 
Description FOF
Amount £132,000 (GBP)
Funding ID EP/J013390/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 05/2013 
End 04/2014
 
Title Nanocellulose surface coated support material 
Description The invention relates to a process for the production of a surface coated support material wherein said process comprises contacting a support material with an aqueous dispersion of nanocellulose. The surface coated support material can be used in a composite material. The invention therefore further relates to the surface coated support material per se, a composite comprising the material, a process for the production of the composite material and an article produced from the composite material. 
IP Reference WO2012049198 
Protection Patent application published
Year Protection Granted 2011
Licensed Commercial In Confidence
Impact Our invention allowed for to engage with Formax UK in a follow on grant and to explore further applications of nanocellulose in composites. A designer uses our process to create novel artwork and display items.
 
Description Imperial Festival 2012 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact The Imperial Festival is a brand new event, celebrating the College through hands-on demonstrations, music, comedy, dancing and art. All activities are free, open to the public and for all ages.

We demonstrated our research activities on the development of hierarchical renewable or sustainable (utilising recycled material) composites to the wider public. Over the two days we spoke to about 1000 people (children and their parent, academics and alumni).

11.-12.05.12.

After the festival, the public is rather surprised by how versatile cellulose is in our everyday life.
Year(s) Of Engagement Activity 2012