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How Tire Engineers Select New Ingredients for Rubber 'Recipes'

December 07, 2011
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With passenger tire sales in the U.S. reaching $21.8 billion last year, tire manufacturers constantly seek a competitive edge by delivering the latest high-tech products to technology-hungry consumers.

In an age when cars can parallel park themselves and drivers can sync their smartphones to automatically broadcast music over car stereos, it makes sense. Just like the gadget makers, tire companies are trying to keep up with technology’s pace – and do so in an industry that traditionally sees longer product lifecycles with slow-to-moderate changes in technology.
In order to continue delivering products that offer improved performance and a reduced carbon footprint, tiremakers are turning to some unlikely ingredients.

Since the invention of the pneumatic tire for automobiles, the basic ingredients of rubber, fabric and steel have been the mainstay components. The concept of reinforcing rubber with cotton fibers to maintain a tire’s structural integrity has evolved into a high-tech, complex recipe of materials that would make the tire industry’s forefathers proud. 

Flash forward a century and the increased demand for tire fuel efficiency and performance from OEMs and consumers alike – juxtaposed against rising raw material prices – have challenged tire manufacturers to dig deep into their design and materials arsenal.

So how do tire manufacturers determine what materials will elevate their products to new levels of performance?

It comes down to asking “What if?” and relying on a team of compound and materials experts to help execute a solution. The problem with adding a “foreign material” to a tire is determining how likely rubber will adhere to that material and form the necessary bonds to integrate it successfully into the structure.

(Not to bore you with the science details, but rubber is finicky when it comes to adhering to fabric, steel or just about anything else. Getting it wrong will lead to reduced tire durability and – sometimes tragically – component separation. The early days of the U.S.-made steel-belted radial provide ample proof of rubber’s nature.)

This presents new challenges to the manufacturing side of the tire business because of the added processing complexity that new materials bring with them. Those tire plants that have the flexibility to add or modify new components into the tire building process and maintain a high level of product quality in a mass production environment will succeed in bringing new technologies to market.

During my tenure as a tire engineer, most of the advancements in tire technology were driven by the research and development side rather than sales and marketing. Creating “new and cutting edge” ideas often meant putting many ideas on the shelf for years and then waiting for the right time to debut the technology. 

For example, during the economic highs of the 1990s when gas-guzzling Hummers and 24-inch bling were common, a majority of consumers were not ready for fuel-efficient tires. Fast forward to 2008 when oil prices peaked and the economy tanked, and now the time was right to unleash the low rolling resistance, fuel-efficient tire technology most tire companies had already been working on.

As the economy slowly recovers, this continuing period of high energy costs and a volatile stock market will keep the industry’s eye firmly on eco-friendly products.

Existing Materials
We’ve also seen other component avenues explored. Toyo’s technology of integrating fragments of walnut shells in its winter tire tread compounds is brilliant. It has taken a byproduct of the food industry and used a green approach to re-purpose the material into a safety-based addition to tires. This is a concept consumers can easily understand and appreciate. 

Anyone who has cracked open a walnut shell knows how sharp the broken bits can be and can translate this into the notion of “enhanced ice and snow traction” for tires. Helping consumers to clearly and quickly see the features and immediately understand the benefits is a successful method of capturing customers.
Another example is Goodyear’s Kevlar-reinforced sidewall technology. When the word “Kevlar” is mentioned, the first image that comes to mind is a bulletproof vest. To the consumer, this translates into “rugged and durable” tires. As government funding for road repair budgets drops, so does the depth of potholes on our nation’s roadways. Consumers will look to products that convey durability and can withstand these types of road hazards.

We can go through a long list of similar marketing-meets-technology examples, but the point is that the investment in integrating new materials into modern tires has to be tempered by a consumer’s ability to easily grasp – and positively react – to the concept.

Ideal Substitutions
Other new materials cropping up in today’s tires are being developed as substitutes for existing ingredients in the rubber formulation. Today’s tire contains a basic mixture of natural and synthetic rubber, sulfur and carbon black, along with other filler materials.  

Synthetic rubber is derived from petroleum, and according to the RMA, it takes approximately seven gallons of oil to produce a single tire. It’s no wonder the cost of tires is skyrocketing. Finding a suitable substitute for petroleum will reduce production costs and increase profits. 

Yokohama’s recent release of its BluEarth-1 tire uses oil extracted from orange peels as a substitution for some of the petroleum oil needed to process synthetic rubber. Some other tiremakers are working with oils from dandelions and even wood pulp. These are certainly steps in the right direction for producing eco-friendly tires. So, what’s next for tires in the future? 

Sumitomo wants to completely eliminate petroleum-based products in its tires by 2013. Toward that end, it is developing its Enasave technology in conjunction with Goodyear. The company is already at a 97% petroleum-free level, and is actively using chemically-altered natural rubber as a substitute for petroleum-derived synthetic rubber.

Elsewhere, vegetable-based oil is being substituted in the processing of tread compounds, and cellulose fibers from plants are being incorporated into reinforcement material. 

There also appears to be a secondary benefit with using non-petroleum-based products. Both Yokohama and Sumitomo have found a decrease in rolling resistance in tires using these substitute materials – and that means less fuel consumption for commercial fleets and consumers.

Michelin has taken another approach in reducing the amount of petroleum in its tires. With its Helio Compound+ technology, the tiremaker has taken sunflower oil and formulated it in the tread compound of its Primacy MXM4 tires. The result is improved wet traction and improved fuel efficiency. This means better stopping distances in low coefficient conditions. Oh, and reduced petroleum-related costs.

Material technology is constantly heading in new and different directions. Today, manufacturers are taking a green approach and are developing products that reduce their carbon footprint in our energy-hungry world, yet deliver the performance and durability that consumers have come to expect since the first tire was mounted on the first car.

With all of these crazy new ingredients, the recipe of a tire is beginning to look more like items on a grocery list. Salad anyone?