For example, to meet stringent European emission and noise requirements, Piaggio recently developed a pair of four-valve, liquid-cooled, low-emission motorcycle engines: a 125-cc model and a 180-cc model. To save money and reduce weight, Piaggio molded the engine covers from 35 percent glass-reinforced Zytel HTN polyamide from DuPont Engineering Polymers (Wilmington, DE).
Piaggio used to make the covers from aluminum. According to Paolo Nesti, design director of Piaggio’s Engine Div., molding the covers from Zytel HTN reduced the cost of the parts by approximately 25 percent and the weight by 40 percent.
The polyamide meets a range of rigorous performance requirements set by Piaggio. "Zytel HTN displayed the best combination of mechanical characteristics and processing ease of any polymer we tested," says Nesti.
Piaggio spent a year subjecting the covers to a range of tests. "We confirmed that the high-temperature performance of this polymer was excellent," reports Nesti.
In the tests, Zytel HTN resisted constant exposure to gasoline, and to engine oils at 140 C. It retained its dimensional stability over a range of impact and burst resistance tests. The material did not distort or warp during testing. "Our tests also showed that engine covers made of Zytel HTN provide far better sound and vibration dampening than other materials," adds Nesti.
For more information about high-performance plastics, call 800-441-0575 or visit http://www.plastics.dupont.com.