Adding tiny amounts of graphene to rubber can make it significantly stronger and stretchier, University of Manchester researchers have shown.

Dr. Aravind Vijayaraghavan and Dr. Maria Iliut, of the university's Nano-functional Materials Group, tested two kinds of rubbery materials: natural rubber, comprised of a material called polyisoprene, and the man-made rubber polyurethane. To these, they added graphene of different kinds, amounts and sizes.

In most cases, they observed that the resulting composite material could be stretched to a greater degree and with greater force before it broke. Adding just 0.1% graphene was all it took to make the rubber 50% stronger.

Thin rubber films are used in a variety of everyday products, such as gloves. Image credit: Pixabay. “A composite is a material which contains two parts, a matrix which is soft and light and a filler which is strong," says Vijayaraghavan. "In this case, we have made a composite of rubber, which is soft and stretchy but fragile, with graphene—and the resulting material is both stronger and stretchier.”

The team used graphene oxide, which unlike graphene is stable as a dispersion in water. The rubber materials were also in a form that is stable in water, which allowed the researchers to combine them before forming thin films using a process called dip molding.

“The important thing here is that because these films are so thin, we need a strengthening filler which is also very thin," says Iliut, research associate in Vijayaraghavan’s group. "Fortunately, graphene is both the thinnest and strongest material we know of.”

The project emerged from a call by the Bill & Melinda Gates Foundation to develop a more desirable condom.

“Our thinking was that if we could make the rubber used in condoms stronger and stretchier, then you could use that to make even thinner condoms which would feel better without breaking," Vijayaraghavan says. “Similar arguments can be made for using this material to make better gloves, sportswear, medical devices and so on."