Fluorescent plastic coating highlights damage and prevents corrosion

A new fluorescent plastic can highlight damage, prevent corrosion, and repair itself to protect coated materials, its developers have said.

Polyphenylene methylene (PPM) was developed and refined by researchers at ETH Zurich in Switzerland, who described their creation as a “miracle material”.

The fight against corrosion on everything from skyscrapers and bridges to ships and aeroplanes is extremely expensive, the researchers said. Countries around the world invest about 3.5% of annual GDP in corrosion protection, they said, amounting to more than $3 trillion.

The material came about partly by accident, according to researcher Markus Niederberger. A researcher in his lab was working on the production of nanoparticles in a special organic solvent, which became solid, or polymerised, under certain conditions. “That was unintentional and unwanted,” Niederberger said. “We didn’t know what to do with it at first.”

They then discovered that the polymer had another interesting property, in addition to high thermal stability – it fluoresced, even though conventional knowledge suggested it should not be fluorescent at all. The researchers set out to refine the material, which is now patent-pending.

When mixed as paint and heated, PPM can be sprayed onto a surface and becomes solid. The polymer indicates holes and cracks in the protective layer by failing to fluoresce.

Laboratory tests revealed that PPM-based coatings can protect metals well against corrosion, especially aluminium. It is also durable, even though the coatings can be applied in layers 10-times thinner than conventional protective agents.

The polymer also seals any damage to the coating by itself, the researchers said. “Self-repair mechanisms are in great demand, but they’re very difficult to attain, and good solutions are still rare,” said researcher Walter Caseri.

Self-repair usually requires chemical additives, which migrate in the polymer over time and are released into the environment. PPM does not require additives, however.

At the end of a product’s life, the polymer can also reportedly be removed and recycled with only 5% material loss. The recycled polymer can then be applied to another surface, with no loss of its properties and functions. In some tests, the material was reused five times.

Studies on the sustainability of PPM-based corrosion protection showed that the polymer performs better than epoxy-based corrosion protection materials on both environmental impact and human health.

“There are really only two disposal solutions for epoxy resins – incineration or landfill,” said researcher Marco D’Elia. “Our product allows for a third solution – recycling.”

PPM corrosion protection is not completely harmless to the environment, however. “Synthetic products always have an impact,” D’Elia said. “But if you choose the right approach, you can limit that impact to a great extent.”

The team is now looking for an industrial partner to further develop the product, and to manufacture and distribute it on a large scale.

The ETH researchers worked with partner universities in Spain, Austria and Italy, as well as in the UK.