The Ole Standby

In the world of engineering polymers, nylon is in a class by itself. When designers want to replace a metal structural part with a plastic one, more often than not, nylon is the first polymer they pull off the shelf.

Because the economic downturn has severely affected the kinds of products—cars and durable goods—that use nylon, the business has been hard-hit. But experts say the trends that benefit nylon, such as reducing automobile weight for better fuel economy, are still going strong.

Nylon refers to a whole class of polyamides, the most common of which in the U.S. is nylon 6,6. Nylon 6,6 has been around since DuPont chemist Wallace H. Carothers first developed it in the 1930s by polymerizing hexamethylene diamine and adipic acid. The next most common in the U.S., although more abundant globally, is nylon 6, which is polymerized caprolactam.

Nylon is most familiar as the fiber used in stockings and carpets, but much of it also goes to making engineering polymers. In 2008, these polymers made up about 44%, or about 4.5 billion lb, of global nylon demand, according to the Houston-based consulting firm Chemical Market Associates Inc. (CMAI). The polymer is ubiquitous in applications that get a lot of wear and tear, such as power-tool housings, door handles, brackets, and structural components found under car hoods or in baby carriages.

“The basic advantage of polyamide is that it combines classic thermoplastic properties—low weight, high design freedom, and high capability of integrating different functions into one component—with its specific material properties, namely high thermal and chemical stability,” says Bernhard Rosenau, automotive segment manager at BASF’s engineering polymers unit. “This enables polyamide to substitute for many metal or other material applications in terms of weight, cost, and performance.”

Despite nylon’s advantages, the severe recession during the past year has dealt a swift and painful blow to nylon producers.

Business was strong for most of 2008 but came crashing down in the fourth quarter, when the financial panic set in, says Mark Murray, director of strategic marketing for Honeywell International’s resins and chemicals business. Honeywell doesn’t make nylon fibers or engineering polymers anymore, but it still produces caprolactam and nylon 6 at plants in Virginia to sell on the merchant market and for its own packaging resins. “Capacity utilization for the caprolactam industry went from 90% in the third quarter down to about 50% in the fourth quarter and the first quarter of 2009,” he says.

According to the trade group American Chemistry Council, sales and captive use of nylon resins in the U.S., Canada, and Mexico declined 40% in December 2008 from the year before. For the full year, demand fell more than 10% to 1.2 billion lb. Demand for nylon in automotive and electrical applications saw the sharpest declines in December 2008 compared with the year before: 57% and 62%, respectively. For the full year, sales and captive use of nylon in auto applications dropped 23%.

“Nylon is pretty heavily influenced by the automotive and construction sectors, and both of those have been impacted globally” by the recession, says David Donofrio, global business manager for nylon at DuPont. “The entire engineering polymer portfolio that DuPont offers is heavily tied to those sectors.”

Engineering applications were indeed harder hit than applications such as packaging, Murray says. In China, however, sales of engineering polymers, which don’t rely as heavily on the auto industry there as they do in the U.S., fared a little better, he adds. But the downturn didn’t spare any sector. “The water level across the board came down,” Murray says.

The industry has adjusted production to the decline in demand. DuPont idled some nylon 6,6 polymerization and compounding capacity in the U.S. this year. BASF reduced caprolactam production at its plants in Europe and the U.S. to 65% of capacity last October. And Rhodia is planning to close a nylon polymerization plant in Italy and a compounding plant in Canada.

There are signs of recovery. Murray has noticed a recent uptick in demand and says operating rates of industry caprolactam plants have climbed back to 75%. Still, such rates are far from healthy, and Murray isn’t expecting a quick rebound. “Because of the demand destruction of 2009, it will take a long time to get back to where we were in 2008,” he says. “This is not a one-year event.”

With utilization rates for nylon polymers starting out the year at only 50% of capacity, the industry has its work cut out for it, notes Adrian Beale, director of global engineering resins for CMAI. The key challenge facing the industry, he says, “is how to reengineer itself to grow demand in the coming years.” He forecasts only about 3% annual growth in nylon engineering polymers over the next five years, down from the 5 to 6% growth seen before 2008.

The nylon industry is up to the challenge, DuPont’s Donofrio says. “Nylon is the place where most designers start,” he says. “It is the most easily tailored, most user-friendly engineering polymer for the automotive market.”

With the auto industry reeling from the sharp decline in sales and the bankruptcy of General Motors and Chrysler, Donofrio sees an opportunity for additional replacement of metal with nylon to reduce weight and cut costs. “The auto companies want to push for fuel economy and reduce greenhouse gases,” he says. “Those are all things that point to nylon.”

For example, working with European auto parts supplier Bruss, DuPont developed what it bills as the first polymer oil-pan module for a commercial-volume vehicle. To appear on Mercedes-Benz C-Class cars, the part is made of cast aluminum and nylon and saves almost 2.5 lb versus a wholly aluminum part. Similarly, BASF helped develop a nylon oil sump for the Mercedes Actros truck series.

The nylon industry is also picking up applications outside of its traditional automotive and electronic equipment markets, BASF’s Rosenau says. To illustrate the point, he cites the Vegetal chair featured on C&EN’s cover this week. Designed by Ronan and Erwan Bouroullec for the Swiss furniture maker Vitra, the chairs are made of nylon.

Still, CMAI’s Beale points out, the outlook for nylon isn’t completely rosy. The polymer’s tendency to absorb moisture leads to poor dimensional stability. And cheaper plastics, such as long-glass-fiber-reinforced polypropylene, poach some nylon applications.

But Rosenau is confident that polypropylene can’t compete in bellwether applications such as car parts that are under the auto hood. “The main application areas of polyamides are relatively resistant against material competition,” he argues, because polypropylene’s thermal and mechanical performance is insufficient for many applications.

DuPont’s Donofrio agrees that polypropylene’s appeal as a nylon replacement is limited and says challenges are still arising that only nylon can meet. As applications mature and requirements are better understood, engineering polymer applications could get downgraded to low-end performance materials, he says. “But typically the design requirements are going up; the temperatures, the environmental exposures are increasing, not decreasing.”

Chemical & Engineering News

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