HANOVER, Germany – Made from renewable raw materials and containing only very small quantities of fossil materials, “green tires” are the stuff of dreams for any tire manufacturer. Chemists at leading tire manufacturer Continental are working on making this dream come true. They are already replacing fossil oils with rapeseed oils and polyester with rayon as reinforcement for the body of the tire.
At the same time, synthetic and natural rubber is being replaced by increasing quantities of recycled rubber from old tires. But in the eyes of Dr. Boris Mergell, Head of Material and Process Engineering for Continental tires, it is a rocky road: “Not all raw materials in tires can simply be replaced by renewable materials,” he explains. “In many cases, such materials have a negative impact on braking performance or rolling resistance – and we will not accept any compromise here. Also, the widespread replacement of fossil materials with renewable raw materials is not always a solution since it requires acreage that might already be used in food production.”
He explains that a standard Continental passenger car tire already contains almost 45% non-oil-based materials. “In terms of environmentally friendly materials, tires are better than their reputation,” he says.
Rubber extraction from dandelion, for example, currently presents a promising potential replacement for rubber extraction from trees. Since dandelion is grown on fallow fields in Europe, it would neither have to compete with food products nor be transported long distances to the European tire plants.
At the same time, carbon black can be replaced with silica (silicic acid) in the compound, explains Mergell. This way, 20% of the weight of a tire could be replaced with “natural” materials. Whether acquired from renewable resources or recycling facilities, plasticizers and resins could also be potentially used in tires.
“We still need to conduct numerous tests on materials and in our process engineering to make significant progress,” he says. He therefore warns against expecting “green tires” to appear overnight. He believes it could take another five years. “But we are heading along a promising path toward this goal.”