A double treat

A liquid-repellent coating process originally developed for the MoD has been adapted for devices such as mobile phones, car parts and aircraft components.

Porton Plasma Innovations (P2i) claims it could coat the outer surface and internal electronics in an electronic device in one step.

P2i, a joint venture between an agency of the Ministry of Defence, Defence Science and Technology Laboratory and Circus Capital Technology, was formed in January this year to work with those who wish to optimise the performance of their products through the use of the treatment.

The technology itself, however, was developed by the Defence Science and Technology Laboratory (Dstl) and the University of Durham to repel water, oil and dangerous chemicals from soldiers’ clothing.

An entire item is placed inside a low-pressure chamber and a fluorinated gas is pumped in, surrounding and penetrating the object. A radio frequency causes the gas to ionize and release free radicals, forming a plasma. The free radicals polymerise on to all surfaces of the object leaving an ultra-thin polymer waterproof coating, even on the interior surfaces.

‘You can deposit this coating on to whatever item you want, whether it is metallic, plastic, fabric, glass or paper,’ said Dr. Stephen Coulson, technical director of P2i. ‘It is so thin it doesn’t affect its characteristics, flexibility or in the case of textiles, its drape quality or breathability. All the benefits of the material are retained.’

Conventional coating techniques require expensive chemicals and high temperatures, but P2i claimed their process is more efficient.

The technology improves on previous waterproof coatings because it coats every surface the gas can reach. ‘It can penetrate right through the open pores of a fabric for example, so as a fabric degrades and takes the coating with it, there are coated fibres underneath,’ said Coulson. The coating is three times more repellent than Teflon, he claimed. However it is vulnerable to wear on solid surfaces such as metal.

The company is currently developing water-repellent medical products and automotive components. A UK filtration company has licensed the technology to improve their vent products for engines, optimising gas passage and liquid-repellence. P2i plans to expand the technology to consumer goods and clothing.

By pumping a different starting chemical gas into the chamber the properties of the coating can also be manipulated. Fluorinated group chemicals give liquid-repellence, while hydroxyl group chemicals allow the water to spread out over a surface, and hydrocarbons and aromatics can provide fire retardation.

The company plans to scale up the technology to coat larger items using a 2,000 litre volume chamber around the size of a telephone box. ‘The processing costs in general are very low,’ said Coulson.

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