The use of polyurethanes in automobile design has been on the rise for several years, but with its growth has come greater expectations and a slate of new issues.
The benefits of the material are well-documented, said a spokesman for the Alliance for the Polyurethanes Industry: increased comfort in seating cushions, better sound and vibration absorption and weight reduction when replacing metals in exterior parts that leads to better gas mileage.
The volume of PU used by original equipment manufacturers has increased 56 percent during the last six years, he said. Among the five largest markets for PU in terms of volume, automotive is showing the fastest growth. Each vehicle contains between 25 and 50 pounds of PU, the spokesman said.
The trend is upward because urethanes offer more design flexibility, said Rich Rossio, a senior scientist with Howell, Mich.-based Chem-Trend Inc. He anticipates further growth because of new applications in development.
More use of urethanes means more concerns, especially in the areas of safety, durability and recycling. The concerns often are new wrinkles to ongoing issues, Rossio said.
``For instance, previously PVC wasn't an issue and now it is,'' he said. ``Head injuries weren't an issue and now they are. It goes on and on.''
Safety always has been in the forefront for carmakers, no matter what material is used, said Frank Womack, Air Products and Chemicals Inc.'s global marketing manager for PU additives.
From a marketing standpoint, safety sells, said Jane Kniss, who handles flexible-foam application development for Air Products. And PU parts usually are a good way to achieve both weight and safety goals, she said.
``Legislation has come out setting tough safety standards, and PU products meet or surpass those standards,'' Rossio said.
He admits the need for lighter, more efficient parts puts greater pressure on manufacturers.
A [lighter-weight part] takes away from something and pushes the envelope every time,'' he said.
For instance, he said, metal bumpers filled with PU foam are lighter but very effective during an impact.
Thermoplastics had replaced PU in many bumpers but ``we're now seeing a resurgence of PU bumpers.'' Companies also are looking at urethane to replace PVC in interior door panels, Rossio said.
Jim Tobias, senior principal application chemist at Lehigh Valley, Pa.-based Air Products, said PU has been replacing steel on high-end vehicles because it is lightweight, has good durability and won't rust.
Seats, headrests, steering wheels, instrument panels, door panels and headliners are among the vehicle components in which PUs are used, Womack said.
In each case, PU met stringent safety and durability requirements, Kniss said. Seating foam, for example, should look the same 10 years later and still be comfortable, and urethane foam meets those requirements, she said.
On a car's exterior, PU has proved to be more corrosion- and dent-resistant, the API spokesman said.
Urethane chemical producers also are developing low-odor, low-fogging materials catalysts and polyols to improve current systems and PU cast skins.
``There are a lot of contributing factors to odors in the car,'' Tobias said. ``We're working on the additives that stay in the foam. Sometimes, when the temperature rises in the car, the odors come out in the form of fog on the windshield. Odors come from a wide variety of materials.''
On the downside, the urethane industry has made little headway in recycling. Cost is the issue.
``The world likes recycling, as long as it doesn't cost more,'' Womack said. ``It's very costly to do.''
Recycling of PU is mandated in Europe, but has not proved to be cost-effective in the United States, said Rossio. Until a cheaper way to recycle is developed, it's not likely to become a major issue, several of those interviewed said.
``It's possible, but it needs the backing of OEMs and government,'' Rossio said.