Update ....CSIRO has not maintained its patents in this work and is no longer pursing its development.

A technological breakthrough by Australian scientists has produced a solution for the world's mountains of waste truck and car tyres.

Every year more than 700 million new car and truck tyres are manufactured and there's not much use for them when they are replaced - most are buried or burned.

"We have a fantastic technology that can turn old rubber tyres into a range of useful plastic and rubber composites that are suitable for many engineering applications throughout the rubber and plastics industry," says the Chief of CSIRO Building Construction & Engineering, Mr Larry Little.

In Australia about 70% of the estimated 11 million tyres discarded annually are still being dumped, used as landfill, or stockpiled.

Tyres can now be recycled and used in shoe soles, automotive components, building products, coatings/sealants and containers for hazardous waste.

"Our new revolutionary surface treatment technology means we can offer the world a solution to its tyre mountain," says Mr Little

The technology has already been proven through the development of rubber ABS (Acrylonitrile-Butadiene-Styrene) composites for EcoRecycle Victoria. The composite uses 50% crumbed rubber to replace plastic, offering an economic alternative to Poly Vinyl Chloride (PVC) plastics.

"These applications represent a huge global market for the new composite products that could potentially consume all the rubber available from tyre disposal in a way that is energy-efficient and environmentally clean," Mr Little says.

Despite environmental concerns, incineration of scrap tyre rubber as a fuel source is currently the most widely used method of disposal. One example is burning tyres to fire cement kilns.

Although burning a kilo of tyre rubber generates approximately 28,600 BTUs (British Thermal Units) of energy, it actually requires much higher energy (approximately 121,000 BTUs) to produce a kilo of raw rubber.

Since most common tyre recycling methods require less than 2,200 BTUs to process about a kilo of scrap tyres into clean crumb rubber, the use of crumb rubber in new products could offer considerable energy savings.

Perfecting the revolutionary technology took six years work by a team of eight scientists, now led by CSIRO's Dr Dong Yang Wu.

"We recognised that rubber has many excellent mechanical properties in comparison to other materials. These include impact resistance, flexibility, abrasion resistance, and resistance to degradation, properties that point to crumbed rubber (produced from discarded tyres) having the potential to be a great engineering material," says Dr Wu.

"A major obstacle in the past has been the limited amount of crumbed rubber that can be mixed with virgin compounds, especially in car tyres for example," she says.

"Usually simple mixing produces a product with poor mechanical performance only fit for unsophisticated products like railroad crossing pads, impact-absorbing mats, and garbage bins.

"The scientific challenge was to discover how to chemically modify the surface of crumb rubber molecules to transform it into a reactive ingredient to effectively grab hold of and combine with rubber or polymers (plastics).

"We developed a simple way to build a molecular bridge using a suitable coupling molecule to make crumbed rubber successfully combine with other materials, which leads to significantly enhanced mechanical performance of the composites.

"In this way, Dr Wu says, "the surface treated rubber crumb may be used in a broad range of high value applications"

Examples of applications include : Shoe soles, automotive components, tyres, non-pneumatic tyres, wheels, building products (roofing materials, insulating materials, window gaskets) coatings/sealants, containers for hazardous waste, industrial products (enclosures, conveyor belts, etc) and many more.

Plastics extruder

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Waste Tire

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