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Graphene Adds Stretch to Natural Rubber, Plastic Films

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Rubber rings used to test rubber-graphite composites. From left, natural rubber alone, natural rubber with graphene oxide added, natural rubber with reduced graphene oxide (University of Manchester)

20 May 2016. A team in the U.K. discovered that adding a small amount of the material graphene creates more stretchable thin films made from natural rubber and plastic. Researchers from the lab of materials science professor Aravind Vijayaraghavan at University of Manchester describe their findings in a recent advance publication of the journal Carbon.

Vijayaraghavan and colleagues from Manchester’s Nano-Functional Materials Group are seeking ways of boosting the strength of elastomers, stretchable materials like natural rubber and polyurethane plastic, found in a wide range of industrial and consumer products. When produced as thin films, elastomers are made into condoms and rubber gloves. Vijayaraghavan received a grand challenge grant award in 2013 from the Bill and Melinda Gates Foundation to develop a “next-generation” condom with graphene to better protect against transmission of the HIV virus, which funded this research.

Graphene is a material closely related to graphite like that used in pencils, consisting of only a single layer of carbon atoms arrayed in a hexagonal mesh pattern. The material is very light, strong, chemically stable, and can conduct both heat and electricity, with applications in fields such as electronics, energy, and health care. Manchester is the center of graphene development in the U.K., if not the world, being the home of Sir Andre Geim and Sir Kostya Novoselov, who received the Nobel Prize in physics in 2010 for their work demonstrating the properties of graphene.

The researchers created composites of natural latex rubber and water-based polyurethane with the addition of graphene in various amounts, particle sizes, and chemistries, and tested the composites on films made with dip molding, an industrial method for manufacturing rubber gloves and coatings on objects for corrosion protection or added grip, as well as condoms. Apex Medical Technologies, a medical device manufacturer in San Diego that uses dip molding, was a partner with Vijayaraghavan’s lab in the study.

The team tested the rubber and polyurethane composites, produced as films with a thickness of 20 microns; 1 micron equals 1 millionth of a meter. The results show a small amount of graphene oxide — 0.1 percent by weight — added to these materials increases their elasticity by 50 percent. Graphene oxide is a more stable form of graphene that dissolves in water, and thus more feasible with dip molding.

While graphene is a conductor of electricity, tests also show the composites, with only small amounts of graphene,  have low conductivity. This is important since the integrity of thin films is tested non-destructively with an electric current, and keeping the conductivity of the material in the same range as rubber or plastic films without graphene means manufacturers can continue using this testing method.

Vijayaraghavan notes in a university statement that his lab is “seeing considerable industrial interest in this area and we hope more companies will want to get involved in the commercial opportunities this research could create.”

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