And through some "tremendous collaboration" with the United Soybean Board (more than 600,000 members), Goodyear has seen that new technology come to fruition.
"The United Soybean Board promotes Goodyear products and provides new opportunities to market this technology to our customers," the tire maker's chief polymer science engineer said. "Farmers invest funds from the board to find new applications for soybean oil. You can take the soybean oil that is a byproduct of the beans grown for protein, which are about 20 percent oil, and then take the food applications and other industrial applications like bio-diesel fuel out of the equation—and there are still billions of pounds of soybean oil available."
Since the key focus is to reduce petroleum-based oils, driven by demands for sustainability and fuel efficiency, Goodyear has found soybean oil to be "domestic, abundant and renewable" and possess the key attributes of naphthenic oils, such as thermal stability and compatibility with rubber compounds.
"It is a renewable resource, compound adjustments are possible and various grades are available," Woloszynek said. "This is a growing trend with one of the lowest environmental impacts for raw materials in industrial-use applications."
Specifically, Woloszynek noted that soybean oil possesses better miscibility with SSBR compared to naphthenic oils, as soybean oil is a better plasticizer with the same viscosity.
"This means better manufacturing capacity and a reduction in the energy needed in overall production," he said. "A lower amount of soybean oil (roughly half) is required to provide the same level of extension. And there is no penalty in terms of processing."
In addition, soybean oil has a very low Tg, or glass transition temperature, remaining softer at lower temperatures than naphthenic oils. While petroleum oils transition at about -50°C , soybean shifts this Tg to about -90°C.
Soybean oil is not entirely a polymer pollyanna, however, as Woloszynek said that improvements in one corner of the performance triangle still can come at the expense of another.
"Soybean oil is good for wet traction, compounded with high styrene and high vinyl, but it took a hit in treadwear when we improved the others," he said. "We can adjust by compounding and we are able to balance the properties and in many cases see an improvement in performance."
Leveraging soybean oil
The novel soybean oil extended polymer was developed into an industrialized material in the Rubber Capital of the World, Akron, and Goodyear's chemical operations business supplies synthetic elastomers, latex products, antioxidants and isoprene monomers around the globe.
The tire maker's emulsion plants in Houston and Beaumont, Texas, provide 1 billion pounds of synthetic rubber annually for both tire and non-tire applications, Woloszynek said.
So how is Goodyear leveraging soybean oil to give the proper performance in these spaces?
"With petroleum oils, stiffness goes up as temperature goes down—it's why your sports car gets no traction in the winter," he said. "The key is to acquire lower stiffness across the entire temperature range, and soybean oil is softer at lower temperatures."
And this is one crux of the problem, Woloszynek said, perhaps the toughest trade-off—getting both wet and snow performance at the same time.
"We have a lot of levers we can pull with soybean oil," he said. "Soybean oil allows a compound to remain flexible across a broad temperature range, improving the balance of wet and snow traction."
Such benefits have found their way to the commercial front lines for Goodyear, as soybean oil has replaced petroleum oil entirely in the company's popular Assurance WeatherReady tire, introduced in 2017.
"We have replaced petroleum oil 100 percent with soybean oil, which has provided a 60 percent overall reduction in petroleum products," Woloszynek said.
The achievement earned Goodyear the Environmental Achievement of the Year from Tire Technology International in 2018.
Soybean oil also is used in the company's Eagle Enforcer All Weather tire, a tire used on police cruisers "where all-weather traction for police forces are critical," Woloszynek said. The use of soybean oil in this case reduced overall petroleum products by about 40 percent.
About the same petroleum product reduction was seen in Goodyear's Eagle Exhilarate tire, introduced in 2019 as an ultra-high performance tire that also is able to balance snow/wet performance, according to Woloszynek.
"Soybean oil is improving performance in multiple products—especially premium products where the rubber meets the road," he said.
And Goodyear is taking the technology beyond tires, as a partnership with Sketchers finds soybean oil being compounded into shoes (initially running shoes) for enhanced wear and stability.
"Sketchers has expanded the technology to a wide range of walking, workplace and casual styles," Woloszynek said. "The pandemic has pushed the timing back a bit but we're very proud to take this beyond tires."
Goodyear looks to continue the expansion of soybean oil technology with further studies, improving toughness and reinforcement without seeing a significant trade-off in elongation.
And OEMs are watching.
"This is providing a ton of flexibility for us," Woloszynek said, adding that Goodyear is in discussions with municipal fleets such as the New York City police and fire departments, as well as the New York-New Jersey Port Authority.
"They have begun to implement soybean oil-contained tires and they are getting great results," he said. "We hope to continue to build on that. Because of these successes and our continued development, we have a long-term goal of fully eliminating petroleum oils by 2040. Soybean oil is delivering for Goodyear."