Tires made from trees — better, cheaper, more fuel efficient

Wood science researchers at Oregon State University have made some surprising findings about the potential of microcrystalline cellulose – a product that can be made easily from almost any type of plant fibers – to partially replace silica as a reinforcing filler in the manufacture of rubber tires.

A new study suggests that this approach might decrease the energy required to produce the tire, reduce costs, and better resist heat buildup. Early tests indicate that such products would have comparable traction on cold or wet pavement, be just as strong, and provide even higher fuel efficiency than traditional tires in hot weather.

“We were surprised at how favorable the results were for the use of this material,” said Kaichang Li, an associate professor of wood science and engineering in the OSU College of Forestry, who conducted this research with graduate student Wen Bai.

“This could lead to a new generation of automotive tire technology, one of the first fundamental changes to come around in a long time,” Li said.

Cellulose fiber has been used for some time as reinforcement in some types of rubber and automotive products, such as belts, hoses and insulation – but never in tires, where the preferred fillers are carbon black and silica. Carbon black, however, is made from increasingly expensive oil, and the processing of silica is energy-intensive. Both products are very dense and reduce the fuel efficiency of automobiles.

In the search for new types of reinforcing fillers that are inexpensive, easily available, light and renewable, OSU experts turned to microcrystalline cellulose – a micrometer-sized type of crystalline cellulose with an extremely well-organized structure. It is produced in a low-cost process of acid hydrolysis using nature's most abundant and sustainable natural polymer – cellulose – that comprises about 40-50 percent of wood.

In this study, OSU researchers replaced up to about 12 percent of the silica used in conventional tire manufacture. This decreased the amount of energy needed to compound the rubber composite, improved the heat resistance of the product, and retained tensile strength.

Traction is always a key issue with tire performance, and the study showed that the traction of the new product was comparable to existing rubber tire technology in a wet, rainy environment. However, at high temperatures such as in summer, the partial replacement of silica decreased the rolling resistance of the product, which would improve fuel efficiency of rubber tires made with the new approach.

More research is needed to confirm the long-term durability of tires made with partial replacement of silica, Li said. Further commercial development of this technology by a tire manufacturer could be undertaken at any time, he said. The newest findings were just published in a professional journal, Composites Part A: Applied Science and Manufacturing.

Tire manufacturing, a huge industry, could also provide another market for large amounts of Pacific Northwest natural fibers and the jobs and technology needed to process them

This advance is another in a series of significant discoveries in Li's research program at OSU in recent years. He developed a non-toxic adhesive for production of wood composite panels that has dramatically changed that industry, and in 2007 received a Presidential Green Chemistry Challenge Award at the National Academy of Sciences for his work on new, sustainable and environmentally friendly wood products.