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Burning Rubber

Polyamide family replaces aluminum, reducing cost, weight and noise

Piaggio SpA, Pontedera, Italy, has found a highly reliable, economical solution for motorcycle engine covers. For several years Piaggio has been substituting thermoplastics for various metal and rubber engine components. Two covers serve on several of the company’s liquid-cooled, low-emission engines developed to meet stringent European emission and noise requirements. 

Specialists at Dupont’s technical center in Cologno Monzese, Italy, recommended 35% glass-reinforced Zytel HTN. The high performance 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,” design director at Piaggio’s Engine Division Paolo Nesti said. Piaggio spent a year subjecting the covers to a range of rigorous tests. “We confirmed that the high temperature performance of this polymer was excellent,” Nesti reported. In the tests, this material 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, in contrast to similar polymers that suffered distortion and warpage problems during testing. “Our tests also showed that engine covers made of Zytel HTN provide far better sound and vibration dampening,” Nesti added.

In adopting covers molded from Zytel HTN over aluminum components, Piaggio achieved cost savings of about 25 percent and a weight saving of 40 percent, according to Nesti. The engine covers are used on Piaggio’s Hexagon, Runner and X9 motorcycles equipped with 125cc or 180cc engines in four-valve, liquid-cooled configurations.

Zytel HTN is a family of high-performance resins based on polyphthalamide (PPA) and other aromatic-aliphatic polyamide polymers. These resins outperform standard nylons and a number of other engineering plastics in retention of useful strength, stiffness and toughness at high temperatures and in humid environments, dimensional stability, resistance to a wide range of oils and solvents, even at elevated temperatures, and ease of processing.—SG

For more information:

Circle 605 - Dupont Engineering Polymers, or connect directly to their website via the Online Reader Service Program at www.RSLeads.com/110df-605

Circle 606 - Piaggio SpA, or connect directly at www.RSLeads.com/110df-606