AKRON (April 3, 2002)—In reviving research recently into polyurethane as a possible tire polymer, Goodyear likened the task to the search for the Holy Grail.
Perhaps the better analogy would be the philosopher's stone, the legendary substance that was supposed to allow alchemists to change base metals into gold.
In either case, the industry's decades-long pursuit of an oligomer-based, injection-molded tire has yielded just about as much success as the centuries-earlier search for the mythical grail or stone.
The use of polyurethane (PU)—a rubbery substance derived by mixing two petrochemical-derived raw materials—as a polymer for tires has run aground countless times in the past. One primary reason: the material's melting point is too low, according to a number of sources who have worked on PU tires.
If a tire made of PU is subjected to a panic brake, or to a dry skid, the surface material can melt, creating a flat spot that makes the tire worthless.
Goodyear—through its recently struck research alliance with Boulder City, Nev.-based Amerityre Corp.—hopes to find that elusive “missing link” that will make PU deliver acceptable road-going performance.
“It appears Amerityre has made some improvements in that area through its polyurethane chemistry,” said Rick F. Vannan, director of advanced process and product technology for Goodyear.
If successful, polyurethane offers a range of advantages, including uniformity, good tread wear, high abrasion resistance and the possibility of lower rolling resistance, Goodyear said.
In spite of these high hopes, though, consumers—and competitors—shouldn't expect a road-going PU tire anytime soon.
“Even if we had a tire that we were confident was ready to go technically, it would take at least another two years of testing before we'd be ready to sign off on it as commercial-ready,” Mr. Vannan said.
Even with this proviso, Goodyear feels the material has enough potential to pursue. “Even if we can make a tire that's only equal to rubber,” Mr. Vannan said, “we'd be way ahead because there's no compounding, assembly is simplified to a few steps and there's no separate curing department.”
For the record, Amerityre claims to have come up with proprietary chemistry and additives that yield a poly-urethane polymer that exhibits physical properties similar or equal to the typical tire rubber, according to Richard A. Steinke, president/CEO of Amerityre.
This advancement, should it hold up under testing scrutiny, would allow those using it to overcome other drawbacks of previous attempts, such as wet grip.
The company, originally called American Tire Corp., is a producer and marketer of flat-free bicycle tires, made with closed-cell urethane foam, and low pressure lawn and garden tires. Amerityre does not intend to get into car tire manufacturing directly, Mr. Steinke said, but wants to develop the technology to do so to a point where it can license the production process.
Goodyear's link to Amerityre came through a former Goodyear technician, James G. Moore, who left Goodyear a few years back to join Amerityre, when it was still based in the Akron area.
Mr. Moore had worked with Mr. Vannan for several years, and the two stayed in contact. A phone call last year from Mr. Moore, now vice president of operations, enticed Mr. Vannan to visit Amerityre in Las Vegas, and he came away sufficiently impressed to ask his technicians to check into the matter further.
That culminated last Aug. 30 with the announcement of the firms' exclusive joint development agreement.
Goodyear has not invested directly in Amerityre, and company executives offer a blanket “no comment” on Amerityre's operating performance, which shows a net loss of more than $12.6 million on sales of only $229,000 in seven years of existence.
Instead, Goodyear is interested in Amerityre's supposed development of what may be a viable compound for production of such tires, the company has said. Goodyear will invest man- and computer-power initially in the “proof of principle” stage of development, Mr. Vannan said. If work at this level yields promise, then the company would move to a more capital-intensive development stage, which would involve prototype production and testing.
This actually is a second go-round for the two companies. In 1988, Goodyear and Urethane Technologies International—a predecessor company to Amerityre—entered into a five-year research contract covering a polyether urethane UTI had under development at that time. That agreement lapsed without further development.
Regarding Amerityre's claims that its prototype car tire can operate for hundreds of miles without air, Mr. Vannan said the injection molded, unreinforced prototype design would be fine for low ground pressure applications like golf carts or lawn mowers.
A tire for any type of road-going vehicle, however, would have to have reinforcing belts and beads and operate in an inflated state, he said.
In fact, the prototype profiled in several trade and consumer magazines and on local and national television is unable to operate with more than a few psi of inflation, since a higher inflation would dislodge the tire from the rim, Mr. Vannan said.
Mr. Steinke and other Amerityre executives acknowledge that a road-going PU car tire would have to have beads and a reinforcing belt, but they said they believe the basic structural design of their prototype offers run-flat capabilities that shouldn't be overlooked.
One independent voice who believes in the theory that oligomers should play an increasingly important role in tires is Jacques Bajer, president of Tire Systems Engineering Inc. in Grosse Pointe, Mich. Mr. Bajer doesn't, however, feel that polyurethane necessarily is the optimal oligomer for this application.
Instead, Mr. Bajer said he believes better tires could be built using a variety of “judiciously chosen” oligomers in conjunction with tire beads and reinforcing cords. Low molecular weight oligomers would allow cast or liquid injection molding of the tire, which would virtually eliminate non-uniformity and greatly simplify the manufacturing process.
The key, though, to such a tire would be in the precision application of the reinforcements, he said. This would require a winding system that most companies to date are unwilling to invest in, he said.
“The tire is an 'anisotropic beast'…a complex composite whose integrity depends on the stress/strain relationship,” Mr. Bajer said. “The problem most companies, or inventors, have is: 'Don't confuse innovation with reinventing the wheel.'”
Other tire companies appear not to have active programs researching PU as a tire polymer, according to a search of U.S. patents for the past five years. References to the material appear in patents for sidewall inserts or coatings (Goodyear) or as a possible inner liner or reinforcements coating (Michelin North America Inc. and Bridgestone Corp.), but not to polyurethane as the primary tire polymer.
Even Amerityre's own patents focus more on the spin casting manufacturing process than on the materials themselves.