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End-Use Case Study

  • Custom TPE Compounds Provides Wiring Harness Warrantable Seal

Wiring HarnessThe undersides of long-haul semi-trailer trucks are subject to a “chemical cocktail” of ongoing abuse. Grimy exhaust and road particulate combined with spraying water, caustic de-icing solutions, and other chemical agents wreak havoc on whatever they contact. One frequent victim of this assault are wiring harnesses, the connection point for the cabling that delivers power from the truck cab back to the trailer.

When a well-known national truck fleet approached Maxi-Seal Harness Systems to design a new modular wiring harness that could be disseminated fleet-wide, Maxi-Seal saw an opportunity to raise the bar and deliver a new level of reliability.

“We wanted to create a new product that would enable us to offer an unprecedented warranty period against leakage and corrosion,” explained Maxi-Seal’s Manufacturing Engineer Eric Doerflinger.

Doerflinger and his team designed a new high-end wiring harness, but their first prototypes, using existing materials, were disappointing due to unacceptable moisture penetration.

According to Doerflinger, two materials at the heart of their device were the issue — at the connection point a rigid housing needed to bond with a flexible thermoplastic elastomer (TPE) overmold and create a watertight seal.

“We called several plastic suppliers and explained our challenge. They would look at their catalog and say ‘try our product number such and such.’ We would, and when it wouldn’t work they would say ‘sorry, that’s all we got,’ ” Doerflinger recalled. “That happened time and time again.”

The situation changed dramatically, he noted, when he contacted RTP Company.

“RTP Company’s representative brought in their TPE specialist, and their attitude was ‘let’s solve this,’ ” according to Doerflinger. “After a few conversations, they went to work developing two materials specifically for us. We tried them, and found that RTP Company pretty much provided the right solution on the first try.”

The resulting custom engineered materials were an RTP 1000 Series polybutylene terephthalate (PBT) compound reinforced with glass fiber for the rigid housing, and an RTP 1500 Series polyester thermoplastic elastomer (TEEE) compound for a flexible overmold which forms a watertight seal. Both compounds provided the necessary chemical and corrosion resistance while bonding so well together that the harness has successfully endured field tests on a fleet of 20 trucks driven 1.6 million miles.

Maxi-Seal’s new Defender product is the result, a commercial wiring harness system offering an unprecedented 10-year warranty. In fact, noted Doerflinger, the innovation has allowed Maxi-Seal to beat out competitors to win all the wire harness business for the national truck fleet, an extremely large order in this industry.

“RTP Company was key in helping us win this very important business,” said Doerflinger. “Their willingness to look at this uncommon application and work with us to find a solution makes them a very valuable partner.”

Maxi-Seal Harness Systems, Inc., of Grandview, MO, is a leader in developing and manufacturing custom engineered wiring harness systems. The company is a subsidiary of Peterson Manufacturing Company, a manufacturer of vehicle lighting products. For more information, visit