Carbon Black and Amorphous Silica in Tires

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While not a nanotechnology per se, carbon black at the individual particle scale is an inherent nanoparticle.  Carbon black, the soot created by the incomplete combustion of hydrocarbons, has been used in tires to give rubber its black color and increase durability since 1910[1][2].  The individual particles of carbon black are approximately 20 to 110 nm in diameter.  Amorphous silica, another compound used to strengthen tires, is also produced from combustion[3].  These individual particles are approximately five to 40 nm in diameter.

The sticky nature of the carbon particles means that they aggregate into covalently linked particles during tire manufacture on the sub-micron scale.  These carbon and amorphous silica particles further agglomerate into spheres or beads of 1-50 microns in diameter and are manufactured as a final product on the industrial scale as beads that range in size from 1 to 10 mm in diameter.  Large industrial suppliers provide these carbon black and amorphous silica compounds to the tire industry for use in passenger, medium truck and race applications.

The Tire Industry Project (TIP) has been developed to engineer nanoparticle additives for tires that can reduce rolling resistance without being harmful to humans or the natural environment.  The research into new tire compounds includes designer carbon black compounds and novel nanoparticle additives.  The goals of the TIP are to halve the rolling resistance of tires, halve the speed of tire wear and to reduce tire weight.  These goals were developed so the tire industry could responsibly meet the needs of industry growth over the long-term.



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This nanomaterial enhances the color, reduces rolling resistance, and increases the durability of rubber compounds used in automobile tires.





Benefit Summary: 

The addition of carbon black to rubber has decreased rolling resistance by 40%. Twenty percent of the fuel consumption of a vehicle is related to the rolling resistance of tires. The addition of amorphous silica and carbon black is a significant contributor to the wear life and edge tear/wear characteristics of tires. These benefits have directly contributed to reductions in greenhouse gas emissions as well as resource consumption. Further advancements in tire compound technology will only enhance these benefits.


Risk Summary: 

There are relatively few risks to human and ecological health as a result of adding carbon black and amorphous silica to tire compounds. There is some risk to exposure of carbon black due to the particle size. This risk is most often expressed as lung disease resultant of exposure at a workplace where combustion of these materials occurs. Long-term exposure to high doses of pure carbon black have also been shown to cause cancer in laboratory animals. Large particulates can cause lung disease to those exposed to heavily contaminated air, but there are often a number of toxic and carcinogenic substances in air pollution besides carbon black. The particles are heavy so they tend to settle in the environment rather quickly, reducing the risks of carbon black relative to smaller particulates.

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