Issue #3: December, 2006
Injection molding of Viton® fluoroelastomer to enhance manufacturing automation, reduce costs and waste

Multi-material carrier gasket of Viton® GBL-S fluoroelastomer (green) overmolded on Zytel® nylon resin in a fully automated, flashless, wasteless, primerless, no post-cure production cell molding process.

Viton® made with APA technology can dramatically improve the overmolding process by making automation easier, reducing waste and improving efficiency.

During the 2005 ACS Rubber Division Expo™, held Nov. 1-3, 2005, in Pittsburgh, USA, DuPont Performance Elastomers, DuPont, ENGEL and Hamilton Mold & Machine collaborated to demonstrate fully automated control and execution of a molding process to produce a multi-material carrier gasket comprised of Viton® fluoroelastomer over DuPont Zytel® nylon resin.

They successfully demonstrated state-of-the art injection molding with Viton® fluoroelastomer. This was accomplished using tools and machines to fabricate a flashless, wasteless, primerless, no post-cure carrier gasket to demonstrate a fully automated production cell concept. The materials selected were Viton® GBL-S and Zytel®. Prior to the show, the compound was extruded to form a continuous cord of 9.5mm diameter (0.375 inch) that was coated with a partitioning agent, before placement on poly reels to ensure uninterrupted feed to the plasticizing screw of the injection unit. This material form proved ideal for the Engel machine and there were no material breaks during the show.

Significant material savings

Innovative automated production cell concept: Injection molded gaskets of Viton® GBL-S fluoroelastomer produced by Desma's flashless, wasteless and all automatic FlowControl cold runner sequential valve gates.

In order to demonstrate an automated wasteless molding process, a valve-gated cold runner was selected. The valve-gated cold runner design is an alternative to compression, transfer or direct injection molding. Significant material savings from using valve-gated cold runners are achieved by eliminating the material waste typically produced from hot runners.

The hydraulically actuated valve gates were designed and built by Hamilton Mold & Machine, which also designed and built the plastic and rubber molds and the cold runner manifold. The dosing and placement of Viton® onto the carrier was accomplished via sequential valve-gate cold runner - essentially four different shot volumes were overmolded to the nylon carrier in a precise sequence. These formed the letters "HMVG" (Hamilton Mold Valve Gate) on the carrier - dosing was 8.5cc, 13cc, 10.5cc, and 6cc respectively for each of the letters, which showed different sealing bead geometry. In order to properly form and fill each letter, a side vent built into the carrier provided an innovative venting design. The sequential opening used for the show part was controlled by screw position via the Engel machine.

New production cell concept

During the Fall 2006 ACS Rubber Mini Expo™ in Cincinnati, USA, DESMA hosted an open house event at their Hebron, Ky., USA, engineering facility. The company showcased a new automated production cell concept - injection molding gaskets with Viton® GBL-S fluoroelastomer using Desma FlowControl cold runner sequential valve gates that are flashless, wasteless and all automatic. (For more information visit DESMA online at .)

DuPont Performance Elastomers also collaborated with Rutil during Plast06 in February 14-18 in Milan, Italy. At its open house event in Varese, Italy, on October 6, Rutil showcased a new automated production cell concept - injection molding grommets with Viton® GBL-S fluoroelastomer using tooling provided by Fort Wayne Mold & Engineering that incorporates cold runner valve gates from Hamilton Mold & Machine. (Visit Rutil online at .)

To learn more about overmolding with Viton® made with APA, contact Theresa Dobel at (US) 330-929-6924 or via e-mail at or visit htp://

Zytel® is a registered trademark of DuPont

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In this Issue...

Choosing the right elastomer for automotive sealing applications

Long term fuel aging tests show advantages of 'APA' polymers

A unique design for automotive sender seals to comply with PZEV regulations

Injection molding of Viton® fluoroelastomer to enhance manufacturing automation, reduce costs and waste

Working together, two global leaders are creating the next generation of biofuels

Performance of Viton® fluoroelastomers in ethanol–fuel blends

Recent events in Asia-Pacific: DPE opens new China Entity, exhibits at Yokohama Auto Show, and presents at Hyundai Kia Research Centre