Interesting new molding technology is quietly being implemented by DuPont in Europe.
A new electronic connector gasket from Dana integrates wiring harness, power connectors and Zytel nylon and Vamac ethylene acrylic elastomer polymers in a primerless bond, reducing assembly time by 30 percent to 40 percent and component cost by 25 percent to 40percent compared with conventional gaskets and separate wiring harnesses.
The multi-shot technology, licensed solely to DuPont by Evonik Degussa GmbH, allows direct bonding of rubber and plastics and simplifies assembly by eliminating the need for primer or anchoring.
Dana Corp., Neu-Ulm, Germany is using the technology in an integrated connector gasket, which includes both a wiring harness and power connectors. The seal made of Vamac is permanently bonded to the gasket body of Zytel to provide long-term heat and oil resistance and to eliminate leaks.
“The greatest challenge was to seal metals, thermoplastics and rubber materials at the open window connector point. We worked closely with DuPont to modify the polymers and develop new process technology to create optimal adhesion between Zytel nylon and Vamac AEM throughout the gasket,” said Berthold Schiele, sales engineer and project manager for plastic systems at Dana. “The adhesion of Vamac AEM to Zytel nylon exceeded our expectations. We subjected the bonded materials to a special pull force test, but the extra force necessary to separate the two far exceeded the actual operating conditions the gasket will meet in long-term service. Consequently, we can see considerable potential application for this technology and materials combination in the future.”
The Dana gasket is the first to integrate wiring harness, all fuel injector, plug, sensor and actuator/solenoid power connections. The first commercial installations in Europe took place from early 2010 in large diesel engines manufactured by MTU, Deutz, and Liebherr, following exhaustive validation and field trials.
In-Mold Hold Pressure
In a separate development, a new In-Mold Hold Pressure (IMHP) technology from DuPont enables significant productivity increases during the injection molding of semi-crystalline thermoplastics. In the case of large shot volumes or relatively short overall cycle times, the time savings can be up to 30 percent.
The IMHP process offers two different methods — each integrated within the mold — for applying hold pressure and the successive feeding of molten material. As part of the first method, a hydraulically operated piston, which is integrated in the movable side of the mold, is immersed in a specially provisioned and appropriately dosed melt cushion.
Alternatively, the equivalent melt volume is available on the stationary side of the mold in the hot runner. In this case, the molten material is pressed into the cavity using a needle-valve-like mechanism. Both methods are currently being tested and refined by DuPont, with a current emphasis on minimizing the additional space required.
“We have conducted numerous injection molding trials with different semi-crystalline thermoplastic grades at our Technical Center in Meyrin, Switzerland, and were able to demonstrate, on the basis of producing standard bars used for tensile testing, the potential efficiency improvements,” said Ernst A. Poppe, European manager for application and processing technology at DuPont Performance Polymers. “IMHP technology is particularly beneficial when molding DuPont Delrin acetal resin, for which the hold pressure time constitutes a large proportion of its overall cycle time. Additionally we were able to demonstrate that there were no significant changes in terms of dimensional stability and mechanical properties between standard injection-molded samples produced with IMHP technology.”