Successful collaborations – A case study
A sustainable plastics industry needs collaborative, marketable innovation to face the complex challenges of mobility and sustainability. The cooperation between REHAU and Trinseo in developing one of the materials used in the new Airbump® technology of the Citroën C4 Cactus is an example of how this kind of innovation can work.
Meeting the specifications
In the fall of 2014, the new Citroën C4 Cactus was launched as an innovative lightweight concept. The automobile manufacturer PSA Peugeot Citroën, the component supplier REHAU AG+CO, and Trinseo LLC came together to develop the side impact protection technology known as Airbump®. The material development within this project is a prime example of efficient innovation performance and included everything from developing entirely new technologies and materials to the creative optimization and reapplication of existing ones.
The Citroën C4 Cactus gives its users a high degree of comfort and individuality. The weight and energy optimized concept aims for both greater efficiency and a lower total cost of ownership. One of the most striking functional and design features is the Airbump® side panel. Consisting of different plastic components, these panels protect the side of the vehicle from damages received during minor collisions (parking dents, shopping carts, etc.). The airfilled polyurethan capsules behind the TPU surface absorb impacts up to 5 km/h by letting the soft material sink in approximately 2 cm without damage. The technical requirements which the materials had to meet for the special production process of Airbump®, were complex. The specifications of the visible TPU surface and the underlying PU capsules determine the specifications for the PC/ABS foundation to which it had to be attached: the lightest possible weight, consistent impact strength even at low temperatures, very high color consistency, form fitting stability, high flow, low cost.
Very good gets even better
Trinseo had already been supplying plastics to REHAU for applications outside of the automobile sector, so REHAU was familiar with Trinseo’s factory and development department in Terneuzen, Netherlands. In 2009, that existing relationship led REHAU to turn to Pascal Desjours, Application and Development Specialist at Trinseo Automotive, for help developing a suitable PC/ABS foundation to go with the Airbump® TPU surface. Trinseo’s global and well-connected network of production sites, as well as the flexible and reliable supply of materials, were confidence-building and decisive factors for REHAU. After the first color consistency tests in Terneuzen, REHAU considered PC/ABS PULSE™ to be the desired material, even though it had previously only been used for automobile interiors. Initially, PULSE™ A35–105 was tested. It yielded better values than expected and showed high transparency with optimum color consistency in tests conducted by REHAU laboratories. However, there was room for improvement concerning the TPU compatibility, weight and cost. That is why the test series was extended to search for an even better solution, with the primary requirement being TPU compatibility in both the production and assembly processes. Meeting this requirement led the joint development team to integrate PULSE™ GX50 into the project, which is the material that was eventually used for the Airbump® production.
Adapting to succeed
For the Airbump® manufacturing process, REHAU attached great importance to having uniform transparency and optimal color consistency in the underlying PC/ABS material. These requirements were easily fulfilled by both PULSE™ A35-105 and PULSE™ GX50, due to the continuous mass polymerization technology Trinseo uses to produce its ABS resins. Compared to an ABS that is produced by an emulsion process, consistent quality and performance is achieved from batch to batch: lower gel content, optimal color consistency, virtually no granulate residue, very good VOC values, and market leading heat resistance.
In addition to color consistency, further REHAU requirements were weight reduction (without loss of strength, impact resistance or scratch resistance) and good spiral flow, which was especially important because the lightweight concept required thin walls for the individual parts.
Finally, the temperature dependent dimensional stability for the PC/ABS foundation needed to be as similar to the TPU surface as possible. Since the components are directly connected to each other by a special process before they are mounted on the vehicle, the engineers wanted dimensional stability values that were as close to each other as possible.
As Pascal Desjours explains, “All of this challenged us and our client to modify an existing material in a highly innovative way. Our PULSE™ series has developed into a material that can be used for exterior applications as well as interior. Ultimately, PULSE™ GX50 was chosen over PULSE™ A35-105.” PULSE™ GX50 is approved against OEM specification FTM 62 0008.
Innovation requires cooperation
Taking an off the shelf product is often the easiest, most pragmatic path. However, customized solutions are needed to solve complex problems such as the ones presented here. As REHAU summarized, “We managed to innovate in the production process as well as with the material itself, and this could only be achieved with a trustworthy partner.“ After this successful, multi-year cooperation, REHAU is considering nominating Trinseo for “Key Innovation Partner“. In the meantime, both companies are collaborating closely on two entirely new projects, and Trinseo is successfully marketing the new PULSE series for exterior as well as interior applications.
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