Hot Gas Welding Provides Competitive Edge

Case Study
Case Study
Hot Gas Welding PPA Thermostat Housings | DuPont™ Zytel®



Engineers at system supplier Bocar Group Plastics Division were thinking outside of the box when they decided to use hot gas welding and DuPontZytel® HTN to create a thermostat housing for the 2017 Ford Motor Company 3.5L V6 Cyclone TiVCT TDI engines.

Application Description

First hot gas welded PPA thermostat housing is a completely new design that not only fits into the very limited space on the Ford 3.5L V6 Cyclone TiVCT TDI engine, but is 30% lighter and 40% less expensive than the previous aluminum solution.

It was developed by Bocar Group, one of the world’s leading providers of aluminum, zinc and plastic modules for vehicle engines. Established in 1967, Bocar Group has earned a global reputation for providing high-quality, innovative products to the automotive industry.

This hot gas welded PPA thermostat housing was a finalist in the Society of Plastics Engineers (SPE) Automotive Innovation Awards competition in the process/assembly/enabling technologies category in 2016.

Unmet Need

Engine downsizing and increased fuel efficiency requirements are ongoing trends that are driving the demand for components and assemblies that are lighter weight; able to fit into the ever-decreasing space on the engine; and capable of delivering required performance in under-the-hood environments that are experiencing higher operating temperatures and pressures.


  • Component must withstand temperatures ranging from -40°C to 120°C and 3.3 bars peak system pressure.
  • Component must withstand aggressive glycol environment.
  • Component must be lighter weight than incumbent metal assembly.
  • Packaging space is at a premium, driving complex design with tight tolerances.
  • High-quality weld joints with no dust in coolant circuit are required.


The engineers at Bocar Group Plastics Division reviewed the list of performance requirements, evaluated the aluminum thermostat housing design and then came up with a better solution by developing the first hot gas welded PPA thermostat housing with multiple joints.

The hot gas welding process enables a high-quality weld joint without dust generation and the tightly packaged innovative design made with DuPontZytel® HTN:

  • Reduces weight by 30% compared to the previous aluminum solution, helping to improve fuel efficiency.
  • Maintains tight tolerance sealing to the engine.
  • Fits into a very limited space on the engine.
  • Costs 40% less than the previous aluminum solution.
  • Meets Ford Motor Company critical performance requirements.

DuPont Material Chosen and Why

DuPont Zytel® HTN51G35HSLR was chosen for this application because it offers:

  • Outstanding resistance to glycol
  • Excellent creep resistance at engine operating temperatures
  • High strength and stiffness over a wide range of temperatures
  • Retention of properties when exposed to moisture
  • Fast molding cycles and excellent flow that allows molding of complex parts



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