A technological breakthrough by Australian scientists has produced a solution for the world's mountains of waste truck and car tires.
Every year more than 700 million new car and truck tires 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 tires 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 tires discarded annually are still being dumped, used as landfill, or stockpiled.
Tires can now be recycled and used in shoe soles, automotive components, building products, coatings/sealants and containers for hazardous waste.
"Our new revolutionary patented surface treatment technology means we can offer the world a solution to its tire 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 tire disposal in a way that is energy-efficient and environmentally clean," Mr Little says.
Despite environmental concerns, incineration of scrap tire rubber as a fuel source is currently the most widely used method of disposal. One example is burning tires to fire cement kilns.
Although burning a kilo of tire 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 tire recycling methods require less than 2,200 BTUs to process about a kilo of scrap tires 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 tires) 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 tires 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"
The actual process and surface treatments used are protected by an international patent with other patents pending," Dr Wu said.
Examples of applications include: Shoe soles, automotive components, tires, non-pneumatic tires, wheels, building products (roofing materials, insulating materials, window gaskets) coatings/sealants, containers for hazardous waste, industrial products (enclosures, conveyor belts, etc) and many more.
For Further Information contact:
Ken Anderson, Manager Communications CSIRO Building, Construction and Engineering.
The above story is based on materials provided by CSIRO Australia. Note: Materials may be edited for content and length.
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