It is important to consider all available opportunities for tire recycling, Kalkstein set out in a Q&A interview for a new ERJ Special Report on Sustainability.*
But asked about the potential role of rCB, the Cabot executive said there are currently significant limitations associated with replacing virgin carbon black with reclaimed pyrolysis carbon.
Indeed, he pointed out that the product is not actually a carbon black: “it is a different carbon material [and] could compromise tire safety and performance if used in more than a small, fractional amount.”
Today’s technology produces a material that is not homogeneous, Kalkstein explained. This is due “to most tires having several different carbon black grades in the various rubber compounds in a tire and many different tire types used in a pyrolysis batch.”
Moreover, he added, the end-product “contains a variable but significant amount of ash – due to the silica used in tread compounds – and has a surface that is chemically quite different to carbon black.
“While [rCB] can be used today in small loadings as a filler or low-end colorant, it cannot currently serve as a substitute for virgin carbon black as it does not offer the same level of performance. “
Summing up, Kalkstein foresaw a role for reclaimed carbon along with other recycled materials in the future, with Cabot continuing to research this area.
But, he concluded, “today there are better uses for this material than as a substitute raw material for rubber grade carbon black.”