MATERIALS | TPEs
Right: Wildo Sweden uses a Dryflex Green bio-based TPE compound for its Fold-A-Cup
standard Dryflex Green compounds show good bonding behaviour to PE and PP but special bonding grades are now available for overmoulding on to ABS, PET and PLA.
Circular solutions
Dannäs says the company is also looking at how its products fit into the Circular Economy concept. “Here, the Dryflex PCW TPE compounds demonstrate how we can turn waste into a resource. The materials contain a volume of post-consumer recyclate from 33% to 80% by weight. Recyclate consists of polypropylene drawn from automotive mouldings, which are cleaned and re-ground, or rubber tyre crumb from both OEM and after-market tyres. Apart from the benefit of recycling and applying the principles of the Circular Economy, the material exhibits excellent UV and weathering resistance, conforming to EN ISO 4892-2:2006 and VW PV 3929:2008 Kalahari Test. The Dryflex PCW compounds are being used in applications such as automotive mud flaps, side- steps and anti-drag lips.” Hexpol TPE also reports that changing and
Below: New TPE grades meet the tighter VOC limits required by automotive OEMs. HVAC is a key applica- tion area
increasingly demanding requirements for automo- tive cabling are driving new developments in TPEs. Mark Griffiths, UK R&D manager, says the company has developed a new cable compound that is halogen-free and provides improved flexibility together with the required thermal and oil resist- ance properties. “Dryflex cable TPEs give halogen-free flame
retardancy (IEC 60754 part 1/2) across a range of hardnesses from 80 to 95 Shore A,” says Griffiths. “With thermal resistance up to 125°C in long-term ageing, they also maintain flexibility at low tem- peratures with a brittleness point at -50°C or lower.”
Another key demand comes from the automotive sector, which is focused on
reducing interior emissions. “In recent
years quality standards for vehicle interiors have
steadily increased particularly with regards to vehicle interior air
quality [VIAQ], where the main concerns are odour, fogging and VOCs [volatile organic compounds],” says Thomas Köppl, Product Manager at the company. “Materials and parts are tested extensively
before they are used in automotive. Firstly, the raw materials undergo tests such as odour according to VDA 270 and FOG/VOC properties with thermal desorption according to VDA 278. Additional testing is done on the components, for example VDA 276, and finally the air of the whole vehicle interior is tested in large chambers [ISO 12219-1 or Chinese regulation HJ/T400-2007]. These tests allow detailed analysis of substances emitted, with many countries setting maximum levels for substances which are known to be hazardous to health, such as formaldehyde, benzene and xylene, for example the Chinese standard GB/T27630. “Emission limits were lowered in recent years both by OEMs and legislation,” adds Köppl. “These reduced levels of critical substances and total emissions can be challenging for some TPS-based compounds, therefore new materials were required. The Dryflex Interior range of TPEs are designed to minimise emissions and can be used in automotive interior applications such as floor mats, cup holder liners, fascia mats and HVAC components. They display low odour with results of 2.0 to 3.0 in standards such as VDA 270. They also show low emission values in regard to fogging and VOCs. According to gravimetric fogging standard DIN 75201, they achieve condensate of less than 1.0 mg.”
Medical benefits Teknor Apex has developed new medical-grade TPEs for injection moulded plunger stoppers that provide improved syringe performance, are less costly and easier to mould than natural and isoprene rubber, and provide processing advan- tages over thermoplastic vulcanisate (TPV) elasto- mers. The company says that stoppers moulded from the new Medalist TPEs perform well in both glass and plastic syringe barrels, achieving a consistent piston release and travel force due to a low coefficient of friction. The compounds can also
72 COMPOUNDING WORLD | June 2018
www.compoundingworld.com
PHOTO: HEXPOL TPE
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