01.01.2021

Super spinifex

UQ researchers are commercialising a class of reinforcing nanofibres that have the potential to create an entirely new industry in rural Queensland.

This UQ team, led by Professor Darren Martin, has demonstrated a highly efficient way to extract cellulose found in the cell walls of spinifex grass and turn it into cellulose nanofibres (CNFs).

These novel nanofibres can be used to significantly reinforce products ranging from condoms to concrete, possessing Kevlar-like properties that add significant strength to a material while only adding a fraction of a percent by weight.

The spinifex grass that the fibres derive from is found across large swathes of Australia’s outback. The harvesting and early-stage processing of this grass is already providing substantial employment and wealth opportunities for Indigenous people in remote areas, as well as increasing involvement of Indigenous people in materials science.

For more than seven years, the UQ team has been collaborating with the Dugalunji Aboriginal Corporation (DAC) – a Traditional Owner business located in Camooweal, QLD – and the organisation has been responsible for the upstream processes of raw spinifex grass ever since.

Facilitated by ANFF and UniQuest, the UQ researchers and DAC are now working with industrial partners to develop this platform technology further and to secure investment as the fibres gather commercial interest.

Reinforcing fibres such as these are typically mixed into a bulk material to improve its strength before being turned into a product. The UQ fibres can be used to prepare stronger rubber, allowing for medical gloves to be made thinner while maintaining their strength; to reinforce paper to better withstand recycling processes and allow for increased reuse; and to be mixed into cement to reduce the amount of material required to construct a building, reducing both costs and environmental impact in the process.

The early stages in producing the UQ CNFs is to breakdown the spinifex by washing, drying, and grinding down the grass to produce a fine powder. Next, the nanofibres are extracted by pulping the powder before hitting it with mechanical energy to separate the CNFs from the mixture, a process called mechanical fibrillation.

As well as being highly efficient, this production process also provides environmental benefits – there’s no need for harsh chemical treatments to deconstruct the spinifex grass and release the cellulose nanofibrils, while the total energy used is also less than that required to produce similar wood- derived CNFs.

The team worked with ANFF at the University of Queensland to characterise the properties and morphology of various grades of CNFs as well as to understand how the fibres worked to reinforce the bulk materials. Professor Martin and the UQ researchers also worked with ANFF’s fellow NCRIS-funded colleagues at Microscopy Australia (MA) who provided assistance on a variety of advanced characterisation techniques.

The results from this work showed that these spinifex CNFs have a high length to width ratio, and therefore a high surface area to volume ratio. This makes them very attractive as a strengthening agent because they can provide reinforcement at very low loadings. The team has also identified that due to their processing technique, their CNFs contained higher levels of flexible “hemicellulose” plant cell wall component, and so tend to be longer and tougher than alternative CNFs that can be derived from wood, for example.

The team’s horizons continue to grow as new opportunities and applications are found and seized upon. Their next steps include aiming to scale up production towards 10’s or 100’s of kilograms per day to meet growing demand.

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