Hexpol has expanded the application scope of its Dryflex Circular thermoplastic elastomer range by obtaining approval to the Porsche PN 780 standard for selected grades with recycled content. The approval covers low volatile organic compound (VOC) emissions and odour behaviour of materials intended for use in vehicle interiors. According to the company, this demonstrates that TPE compounds containing recyclate can comply with demanding automotive specifications that have traditionally been met with virgin materials.
The Porsche PN 780 standard defines test methods and limit values for odour and VOC emissions from materials installed in the passenger compartment. It is intended to ensure low-emission and low-odour components, thereby supporting improved indoor air quality and occupant comfort. For materials suppliers, passing this standard requires detailed analytical testing of individual substances as well as total emissions across a defined set of conditions.
Dryflex Circular TPEs with PIR and PCR recyclate
The Dryflex Circular TPE portfolio incorporates varying levels of recycled content, up to approximately 75 percent, depending on grade and targeted end use. The recyclate sources include both post-industrial recyclate (PIR) and post-consumer recyclate (PCR). Selection of the recyclate stream is tailored to the performance, processing and regulatory requirements of the specific application.
Within this range, the Dryflex PIR 853317-2 TPE grade was evaluated against Porsche PN 780. This compound contains 45 percent recyclate and was subjected to VOC emission and odour testing according to the specification. The measurements covered individual chemical groups such as amines, formaldehyde and ketones, as well as total volatile organic compounds (TVOC). Hexpol reports that all measured individual substances and the TVOC value were significantly below the limits set in the standard.
Odour performance was additionally assessed in accordance with VDA 270, a method issued by the German automotive association Verband der Automobilindustrie for evaluating the odour characteristics of materials used in vehicle interiors. Dryflex PIR 853317-2 achieved a rating of 3.0 in this test, which corresponds to an odour impression that is not disturbing to occupants' comfort under the test conditions.
Reduced product carbon footprint versus virgin TPE
Alongside emission and odour performance, Hexpol has analysed the product carbon footprint (PCF) of the Dryflex PIR 853317-2 grade. The company states that this material shows a 43 percent reduction in CO2e per kilogram of TPE compared with an equivalent virgin TPE compound. This PCF reduction is attributed to the use of recyclate in the formulation, in line with automotive OEM targets to increase recycled content and lower the climate impact of interior components.
Commenting on the qualification, Dr.-Ing. Thomas Köppl, global head of product management, said: "These VOC and odor requirements are extremely challenging to meet, even with virgin materials. I'm proud that we've achieved them using TPEs that contain recyclate. It is another example of how Hexpol is enabling automotive OEMs to address both passenger comfort and recyclate targets".
Potential interior applications
According to Hexpol, the low VOC Dryflex Circular TPE grades are suitable for a range of automotive interior components. Typical applications include inlay mats, floor mats, sealing elements and interior trim parts, where a combination of mechanical performance, surface quality, low emissions and odour neutrality is required. The approval to Porsche PN 780 provides a reference for use of these materials in programmes where strict in-cabin air quality specifications apply.
