Nylon had been used as molding resin as early as 1941 — two years after its debut — in self-lubricating bearings. From the late 1940s to early 1960s, nylon was focused on less critical automotive applications, DuPont scientists Eric Carlson and Ken Nelson wrote in a 2003 article about nylon's automotive past.
These applications included valve stems, wiring clips and windshield wiper systems. One significant early automotive nylon use came in 1956 when French carmaker Citroen used it to make the first plastic radiator fan.
In 1960, the average car used less than half a pound of nylon. By 1995, that number had mushroomed to almost 9 pounds of nylon per vehicle. The nylon per-car total would hit 11 pounds by 2000 and surpass 14 pounds by 2005.
A major breakthrough came in 1968, when DuPont researchers found a way to reinforce the firm's 6/6 resins with glass and minerals. This made it easier for the material to be processed, and opened the door for nylon to be used in radiators, fuel systems and many other under-hood applications.
“Nylon challenged creative engineers and designers to toss convention aside and expand the envelope of nylon properties to new limits,” Carlson and Nelson wrote.
Mayo added that nylon “has the unique capability to handle a mix of high temperatures under hood and chemical resistance through exposure to road salt, hot oil, gas and exhaust.”
The additions of glass and minerals enhanced nylon's performance, he said, with typical glass loadings of 25 to 35 percent, although nylon compounds with loadings as high as 60 percent have been commercialized.
“As nylon has evolved over the years, a lot of work has been done to expand its performance,” Mayo explained. “It can handle higher temperatures than before. We've promoted usages as high as 230° Celsius.”
When nylon entered the auto market, “it really became the first engineering plastic,” said Paul Blanchard, engineering resins director with the IHS Chemical consulting firm in Houston. “It had strength, heat resistance and chemical resistance. Those are the big three characteristics you need for automotive.
“And when you put glass in, it adds a significant amount of heat resistance and also improves strength,” added Blanchard, who joined IHS in 2007 after spending most of a 30-year engineering plastics career with GE Plastics. “That allowed nylon to compete with metal.”
Initially, the addition of glass to nylon was held up by primitive single-screw extruders, Blanchard explained.
“It took a while to design better screw configurations,” he said. “Twin-screw extruders worked better and had different venting.”
Nylon also got an auto-related boost in the 1970s when government regulations began to require pollution control devices on new vehicles. To keep the weight of these devices down, many of them would be made from nylon.
By the 1980s, nylon dominated fuel efficiency and emission control technologies. The material was used in integrated molds and in snap-fit assemblies. Nylon was used in air intake manifolds in Europe in the 1970s, with its use in those parts spreading elsewhere in the 1980s.
Parts integration then provided a good part of nylon's appeal, according to DuPont's Mayo. “Automakers had observed over the years the ability of nylon and plastic in general to integrate components,” he said. “So instead of five or 10 or 15 metal parts — which could be very difficult and expensive to assemble and heavy — they can be replaced by one or two nylon moldings that can be snapped together or screwed together.
“That would bring in nylon in a very cost-effective way,” he said. “Nylon's advancement was about systems cost as much or more than weight reduction. It could bring value — if you were looking for design and versatility — while taking complexity out.”
In the 1990s, the first high-volume commercial air intake manifolds were made in the U.S. by General Motors and DuPont's auto unit. The material also proved useful in supercharged and turbocharged smaller engines in the 1980s and 1990s. Nylon even was used in what Carlson and Nelson described as “air resonators and fuel tanks with Salvador Dali-like shapes.”
Future is strong
And even more automotive innovation might lie ahead for DuPont and other nylon makers.
“The drive toward cost and weight reduction favors nylon,” said Blanchard, who also praised DuPont's Zytel Plus nylon line and similar high-heat resins introduced recently by other producers.
“It's real apparent now that nylon has gone through a rebirth or evolution and it keeps advancing,” he added. “The new technology extends the age of parts in high-heat environments.”
From that first DuPont plant in Seaford, the nylon market has grown to encompass more than 20 billion pounds of combined resin and fiber capacity worldwide. German chemicals giant BASF SE joined the market shortly after DuPont did, and numerous other companies would enter the field. DuPont and BASF remain in the market today, along with U.S.-based producers Invista, Ascend Performance Materials Inc. and Honeywell International Inc.; European producers Royal DSM (the Netherlands), Lanxess AG (Germany), Radici Group (Italy) and Solvay SA (Belgium); and Asian producers Ube Industries Ltd. (Japan), Formosa Group (Taiwan) and Shenma (China).
The market also has expanded beyond nylon 6/6 to include nylon 6 — another widely produced grade — as well as specialty grades such as nylon 12. Globally, about half of nylon resin production is consumed by the automotive market.
(In a sign of the times, DuPont exited the nylon and polyester fibers business — which had become a high-volume, low-margin business — in 2004 when it sold that unit to Koch Industries Inc. for $4.4 billion Koch kept the business going under its well-known Invista trade name.)
Beyond automotive, DuPont's Mayo said that nylon has found a home in many electrical and electronic applications, including laptop computers, smartphones and gaming consoles, where it's often replaced metal. These applications offer lower consumption than the auto market does, he said, but still allow nylon to provide good value.
Nylon also appears to have a bright future, based on the new high-temp materials cited by Mayo and Blanchard, as well as on the recovering global auto market. The number of nylon capacity additions announced in the last year alone also is an encouraging sign.
In that span, DSM has announced plans for a new nylon resin plant at an undisclosed site in North America, and Honeywell confirmed plans to add almost 90 million pounds of resin capacity in Chesterfield, Va.
In Europe, Lanxess opened a plant with almost 200 million pounds of capacity in Antwerp, Belgium, in July, while Evonik Industries AG added 11 million pounds of capacity for specialty nylon 12 in Marl, Germany, in June. Those moves followed the late May announcement that Polish chemicals firm Grupa Azoty planned to open a plant with almost 180 million pounds of annual nylon 6 capacity in Tarnow, Poland, by 2016.
BASF also bolstered its nylon assets in China earlier this year by adding more than 100 million pounds of compounding capacity for nylon and PBT at its plant in Shanghai.
Although DuPont has no nylon expansion projects at present, Mayo said that the firm “is continuously looking” at its investment needs. “It's important for us to be able to supply our customers, and to be responsible and flexible.”
At IHS, Blanchard added that he's “bullish” about the future of nylon.
“Nylon is a workhorse material that functions nicely across a range of products,” he said. It's kept pace through development, and I don't see any danger that it will slide in the future.
“There's a lot of life left in this baby.”