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Plastic that melts to ceramic

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The ceramifying polymers have been developed by CSIRO and the CRC for Polymers, and are being commercialised by CRC spin-off company Ceram Polymerik.

The ceramifying polymers were developed for use in fire-resistant electric cables, by combining properties of a polymer with those of a ceramic.

As the polymer melted and disintegrated in the heat, the ceramic formed a solid protective insulative layer, preventing short-circuits and enabling the current to keep flowing.

Typically polymers start to melt between 100 and 200 degrees and disintegrate completely around 300-400 degrees, whereas ceramics are typically formed at temperatures of 700 degrees and above.

The trick was to develop materials that were stable between the degradation of the polymer and the formation of the ceramic.

The ceramifying technology may be used for rigid extrusions, flexible seals, foams, sheet, mouldings, mastics, sealants, putties and has potential in protective coatings, according to Vince Dowling, from CSIRO Manufacturing and Materials Technology .

Ceram Polymerik chief technology officer Kevin Thomson told Australian Mining that the innovation was a combination of ceramics technology with polymer technology.

“The ceramic technology is very important because a high level of an organic material is mixed with the polymer. There has to be enough organic material in the polymer to form the ceramic. All this has to happen at a low enough temperature, so the structure can be maintained from normal service temperature to fire temperature of more than 1000 degrees centigrade.

The ceramifying polymer compound is complicated, says Thomson, because it contains many different ingredients that must work together in the right way.

“There’s also quite a few challenges on the polymer side because there’s a high level of organic materials in the compound that makes the materials difficult to produce and difficult to process,” he said.

Applications

Thomson said the technology could be used in the mining industry for switchboxes, and pipe and hose protection.

“We’ve done some work with wrapping sheets of our material around pipes with results,” he said.

“Because the material expands it provides an insulation characteristic that forms a hard ceramic barrier which provides a lot of fire resistance.

Foam materials with similar properties are also under development.

“We think the foam materials will be very good for filling in gaps because they’re flexible, that will be easy to install,” Thomson said.

“In a fire it will turn into a ceramic residue again and provide us with that fire barrier characteristic.”

Although the ceramifying technology can improve fire safety it does necessarily make the material non-inflammable, according to Thomson.

“It can certainly improve the fire performance characteristics but what we have to do is include a flame-retardant system in there as well just as you do with a conventional polymer. That makes the material even more challenging because there’s an awful lot of stuff that we’ve got to get inside that plastic,” he said.

Thomson emphasised that the ceramic created from exposure of the polymer to heat or flame was more porous than ceramic used in everyday materials such as a coffee mug. This porous property limited the ceramic’s strength.

“The ceramic is designed to support its own weight and stay where it’s supposed to, so it can act as a fire barrier. It’s actually much stronger than some of the chars from intumescent paint systems, for example.”

An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection.

The polymer technology for cable products, developed with cable specialists Olex, is expected to earn $75m over the next five years.

Ceram Polymerik’s recent first export order was for material to enable UK-based Lorient Polyproducts Limited to manufacture door edge protectors for fire doors. They are currently working with Ceram Polymerik on several passive fire protection products.

Lorient is an acknowledged world leader in sealing systems for door assemblies embracing fire protection, smoke control, acoustic insulation and weather exclusion.

The technology originally evolved from several years of research by the Cooperative Research Centre for Polymers, in conjunction with Olex Australia , the first company to commercialise the technology with the 2004 release of its Olex Pyrolex Ceramifiable high performance fire cable.

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