Natural rubber from dandelions

Dr. Neil Canter, Contributing Editor | TLT Tech Beat August 2011

A Russian flower may hold the answer to a worldwide shortage.

KEY CONCEPTS
• A worldwide shortage of natural rubber means there is need for developing an alternative to the only known commercial source, Hevea brasiliensis.
• Rubber produced from the Russian dandelion, Taraxacum kok-saghyz exhibits comparable performance.
• Efforts are now underway to commercialize Taraxacum kok-saghyz, which can be grown in the U.S. and Europe.

Natural (cis-1,4-polyisoprene) and synthetic rubbers are used in two applications that impact the performance of lubricants. The largest use for rubber is in tires where it has a significant influence on how efficiently an automobile operates. According to the U.S.-based Rubber Manufacturers Association (1), tire formulations contain both natural and synthetic rubber. Interestingly enough, this organization indicates that the content of natural rubber is much higher in a truck tire than in a passenger car tire.

A second application for rubber is its use in seals that are vital to keep lubricant from leaking out of a system while making sure that contaminants such as dirt and water stay out of a system. Seals used in industry are prepared from a number of polymer types including nitrile butadiene rubber, fluorinated silicone and polytetrafluoroethylene.

Bill Ravlin, associate director of The Ohio State University’s Ohio Agricultural Research and Development Center’s (OARDC) Wooster campus in Wooster, Ohio, says, “A strong need exists to develop an alternative source of natural rubber because this material is a critical component in tires. Currently, the only known commercial source of natural rubber is from the Hevea brasiliensis, found in the Brazilian rubber tree.”

Originally natural rubber was obtained from South America, but that plant was wiped out by disease, and the market shifted to Southeast Asia where it has remained. Ravlin says, “In tires, natural rubber is preferred because it provides better adhesion and heat dissipation than all types of synthetic rubbers. As the amount of stress on a tire increases, a higher percentage of natural rubber is incorporated into the formulation.”

Ravlin agrees that larger tires use a greater percentage of natural rubber. He adds, “Airplane tires are prepared exclusively with natural rubber.”

Currently, there is a shortage of natural rubber worldwide. Ravlin maintains that synthetic rubbers could be developed with the properties of natural rubber, but the cost would be very high. A second problem is the synthetic rubber would probably be derived from petrochemicals, which already are increasing in price and decreasing in availability because they are produced from crude oil.

Preparation of rubber from a second natural source is desirable. Ravlin says, “More than 2,000 plant species produce natural rubber. Some of the types can be found in the garden, including dandelions, milkweed and goldenrod. Another species that produces rubber is lettuce.”

But Ravlin points out that not all natural rubber from these plants is the same. “A broad spectrum of rubbers have been isolated from plants, but most do not exhibit the properties of natural rubber,” he says. “These rubbers do not have the molecular weight, physical and chemical characteristics and the fatty acid content of the material obtained from Hevea.”

A second source of natural rubber has been known for some time. Efforts are now underway to commercialize this material which comes from a very different plant than Hevea.

TARAXACUM KOK-SAGHYZ
Ravlin says, “Our objective is to domesticate and commercialize the ‘Russian Dandelion,’ Taraxacum kok-saghyz (TKS). This is a plant that grows naturally in Russia, Kazakhstan and Uzbekistan. The U.S. evaluated TKS as part of its Emergency Rubber Program (ERP) during World War II.”

The OARDC has established PENRA, the Program of Excellence in Natural Rubber Alternatives, and is working in conjunction with academic and industrial partners to achieve this goal.

Figure 3 shows an image of the TKS plant that produces natural rubber. TKS is an attractive source of natural rubber because work conducted during World War II showed that sufficient material could be obtained to manufacture tires. Two rubber companies road tested tires at speeds up to 60 mph and found that the TKS-based natural rubber worked well under severe conditions.


Figure 3. The Russian dandelion, Taraxacum kok-saghyz (TKS) has emerged as a viable commercial source for natural rubber. (Courtesy of The Ohio State University’s Ohio Agricultural Research and Development Center)

Ravlin says, “Renewed interest in TKS is also due to where TKS can be grown, which is throughout the Midwest region of the U.S.”

TKS produces natural rubber that is close in performance to that of Hevea. Compounded formulations containing natural rubber from TKS displayed similar performance in laboratory tests. Physical performance tests such as tensile, tear and hardness generate data that is comparable to natural rubber derived from Hevea.

But there are challenges in production of large quantities of TKS that are similar to domesticating other crops. Ravlin says, “We need to work with a wide range of genetic materials and see how they respond in a variety of environmental situations. A plant that does well in the state of Ohio may not be suitable for the state of Nebraska.”

The OARDC is in the process of building a pilot plant to produce sufficient quantities of natural rubber from TKS for further testing and optimization. Ravlin says, “We envision this plant will be finished by the end of 2011. This will enable our industry partners to do additional testing to better understand how to work with TKS natural rubber.”

One new partner is Ford, which will be looking at the natural rubber to provide increased durability in plastic components. Ravlin says, “Ford is looking at TKS natural rubber to increase the amount of biobased materials used in vehicles.”

Additional information can be found at the OARDC Web site (www.oardc.osu.edu/penra), in a past presentation (2) or by contacting Mauricio Espinoza at Espinoza.15@osu.edu.

REFERENCES
1. Rubber Manufacturers Association Web site: www.rma.org. 
2. Ohlemacher, C., Seiple, R., Kleinhenz, M.D., Michel, F.C. Ravlin, F.W. and Ehrensing, D. (2009), “Taraxacum kok-saghyz (TKS) – A Domestic Source of Natural Rubber: Rubber Quality of Early Development Samples,” Presented at the Fall 176th Technical Meeting of the Rubber Division, American Chemical Society, Pittsburgh, Pa.

Neil Canter heads his own consulting company, Chemical Solutions, in Willow Grove, Pa. Ideas for Tech Beat items can be sent to him at neilcanter@comcast.net.