For stronger condoms, spike them with spinifex

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It’s prickly and tough but compounds from spinifex grass can reinforce other materials.

Rough, spiky grass is the last thing you’d expect on a condom production line.

But spinifex grass, native to Australia, is not only set to make stronger and thinner latex condoms – its unique fibres may be the key ingredient for low-cost carbon fibres and tougher construction materials.

While Indigenous Australians traditionally used the sticky sap of spinifex grass to attach spearheads to wood and seal water containers, in 2008 University of Queensland scientists in Brisbane, Australia, led by Darren Martin began investigating the grass for modern use.

They extracted spinifex’s “nanocellulose” – fibres found in plants cells which can be used to make paper and textiles, or added to reinforce other materials like plastics. The team harvested and chopped spinifex grass to a pulp, mixed it with sodium hydroxide and forced it through a small hole at high pressure, which peeled the fibres from the rest of the material.

Compared to other plant fibres, spinifex nanocellulose looked longer, thinner and “stretchier” under a microscope.

And when the scientists added spinifex nanocellulose on a commercial condom dipping line in the US, they found it boosted flexibility and strength. According to Martin, just 0.1% nanocellulose added to latex during production increased the pressure condoms could withstand by 20%, and volume by 40%, in a conventional “burst test”.

The team says the added strength could allow condoms and other latex products such as surgical gloves to be manufactured as thin as a human hair, improving sensation while remaining durable.

Other projects for spinifex are already underway. For one, the scientists are investigating how to stitch nanocellulose into building materials to create high-strength concrete and bitumen that stays tough in soaring temperatures.

Last month, the Queensland government announced $480,000 in funding over three years to develop and commercialise spinifex nanocellulose for latex products and construction materials.

The team is also working on weaving spinifex nanocellulose into carbon fibres.

“The world’s got a pretty big appetite for lower cost carbon fibres for aeroplanes, wind turbines and electric cars, but the cost is too high,” Martin says.

“We have some good indication that adding a little bit of the nanocellulose would enable us a lower-cost, more renewable carbon fibre.”

It’s currently not known why spinifex produces this unique nanocellulose, but Martin speculates the fibres protect the plant’s cell walls from becoming brittle in the dry Australian conditions: “Our botanist and geneticists are telling us there’s nothing quite like it.”

The team is working with traditional owners of the Camooweal region in Queensland, the Indjalandji-Dhidhanu people, who Martin says have had custodianship of spinifex savannas for tens of thousands of years.

The good news is there’s plenty of raw material to satisfy potential demand.

“Hypothetically speaking, if the largest condom manufacturer in the world put half a percent in every condom they make, for a one-year supply we would have to harvest 15 tonnes of spinifex,” Martin says. “That’s not much. We could harvest that by hand.”

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