Low fogging materials for automotive interiors

In a move to improve passenger comfort, legislation regarding odour, fogging and VOC/FOG emissions has increased in recent years, OEMs such as Daimler and VW have also tightened limits. Several countries regulate the maximum allowed concentration of substances which can be hazardous to health, such as formaldehyde, benzene and nitrosamines (for example the Chinese standard GB/T27630).

Hexpol TPE supplies a portfolio of TPE materials optimised for automotive interior applications. Dryflex Interior is a series of compounds which are optimised for low emissions. They offer on average a 75 % emission reduction compared to other TPEs for interior applications on the market. They display low odour with results 2.0 to 3.0 in standards such as VDA 270. According to gravimetric fogging standard ISO 6452 they achieve condensate < 1.0 mg and achieve VOC results from 60 to 120 µg/g and Fog from 200 to 600 µg/g. The TPEs of this series have passed additional interior tests for lightfastness, flammability and mechanical performance. They are currently available in hardness between 25 and 85 Shore A in customer specific colours as well as black and natural.

Method Typical OEM requirements Currently used TPE for automotive interior Dryflex Interior TPE
Gravimetric fogging (ISO 6452) ≤ 2.0 mg 1.0 – 2.0 mg 0.3 – 0.7 mg
Thermodesorption (VOC, VDA 278) ≤ 500 μg/g 100 – 400 μg/g 60 – 120 μg/g
Thermodesorption (Fog, VDA 278) ≤ 1500 μg/g 2000 – 3000 μg/g 200 – 600 μg/g
Odour (VDA 270, B3) ≤ 3.0 3.5 – 4.0 2.0 – 3.0
Emission values of Dryflex Interior TPE (Source: Hexpol TPE)

The company has also announced an expansion of the Dryflex Green range of biobased TPE compounds. These TPEs incorporate a high amount of raw materials based on renewable resources such as sugarcane. Depending on the hardness of the TPE, a renewable share of over 90 % is possible. Properties and processability are similar to regular fossil-based TPE compounds. Dryflex Green TPEs with low emission values will be presented at Fakuma, for example a 65 Shore A compound with a renewable content of 40 % showed a very low amount of VOC (82 µg/g) and Fog (142 µg/g) in the thermodesorption test according to VDA 278. Dryflex TPEs for automotive interiors can be used in applications such as inlay mats in the dashboard, door, middle console or glove box. They are also well suited for thumb wheels, switches, cup holder liners, interior trim and HVAC components.