POM grades answer new interior emissions standards

German automaker Daimler has implemented 50% stricter monomer emission limits for added comfort in vehicle interiors as of 2012 and this places more demanding performance requirements on resins such as acetal (POM), which emits formaldehyde. The latest low-emission Hostaform POM grades from Ticona (Sulzbach, Germany) are reportedly up to the task.

Fastening systems used in auto interiors typically employ POM components. Ticona's Hostaform POM XAP² grades have a specification limit value of less than 2 mg/kg (2 ppm) formaldehyde emission for uncolored natural POM and less than 5 mg/kg (5 ppm) for colored or custom grades. These XAP² grades are able to meet the stringent limit values of Daimler, which are stricter than Guideline VDA 275 of the German Association of the Automotive Industry (VDA, Frankfurt).

A.Raymond (Grenoble France) and Johnson Controls (Milwaukee, MI) teamed up with Ticona to employ the new grades in fastening systems for seat covers for the latest Daimler B-Class. A.Raymond's clip development takes the specific properties of the material as well as the processing method into account, as both factors influence emission values. The fastening clips permanently connect the seat covers to the seat construction.

Notes Martin Müller, construction plastic and material consulting at A.Raymond, "The new emission values were included in the release of the revised Daimler specification of August 2010. At this time, we were well underway with the development of this fastener clip. This is why we changed the material from a competing product to Hostaform XAP, with which we achieve an emission reduction of around 40%. With the latest XAP² generation and the optimization of process parameters, with the aid of Ticona, we were able to cut emission values in half once more." A.Raymond also found that thin-wall functional components could not produce the values that standard panels could achieve [using other POM grades]. "But with the use of colored Hostaform XAP² grades, Daimler values can also be reached for thin-walled functional components as well," says Müller. An essential requirement for the new formulations was to adapt XAP to cater to needs with regard to interior colors, even critical colors, without losing any of their low-emission properties.

Even components that are not directly in the vehicle interior, such as door modules or seatbelt pre-tensioning systems, increasingly call for low-emission materials. Other potential applications include head rests and lumbar support, fastening solutions in the door area and trim for door elements, instrument panels and center consoles.

Besides standard grades, Ticona also offers several special customized grades: modified impact-resistant grades are suitable for cable clamps or the airbag area; those displaying increased stability on the other hand are good for belt retraction systems. Tribologically modified XAP² is applied for window regulators or sunroof sliders and colored or UV-resistance grades of the product range for the design of visible elements and design components such as high-quality loudspeaker grilles.

The German automotive industry has responded to a global trend in automotive manufacture with regard to the emission of polymers in vehicle interiors. The aim of these efforts is to optimize the well being of drivers and passengers. Stringent regulations on the improvement of the climate of vehicle interiors have already been enforced in Asia and other markets are certain to follow shortly, according to Ticona. —[email protected]