Automotive Design
Fig. 1. DSM’s hydrolysis resistant PET is aimed at dimension-critical underbonnet components.
More than a weight issue
4 The main reason for specifying plastic in cars is to save weight – but they can deliver other benefits too. Lou Reade reports.
4 Prescrire du plastique dans les voitures se fait principalement pour les alléger, mais les plastiques ont également d’autres avantages. Lou Reade témoigne.
4 Der Hauptgrund für die Spezifizierung von Kunststoff in Autos ist, Gewicht zu sparen – es gibt aber auch noch andere Vorteile. Lou Reade berichtet.
T
he overwhelming reason for using plastics in cars is the same as ever: to save weight. If a fenders, bumpers, accelerator pedals and other parts can be made from
plastic - which is around half the density of an equivalent steel part - this frees up ‘space’ to add other elements such as more robust safety features. But plastics must do more than simply save weight. They must also meet the ever-more stringent requirements of the automotive industry – whether it is higher engine temperatures, easier recyclability, design freedom or, as ever, reduced cost.
Under-bonnet advantage
Dutch chemicals specialist DSM has developed a hydrolysis resistant grade of polyethylene terephthalate (PET). Arnite A HR could be used to make dimension-critical components under the bonnet, in place of metal or more expensive polymers.
Continuous engine downsizing, especially
for compact cars, has led to higher under- bonnet temperatures and puts higher demands on plastics components. DSM says there is a demand for materials that retain properties such as strength, stiffness and impact strength under these conditions. “Injection moulded parts from conventional
PET lose as much as half of their tensile strength after 1000 hours at 85°C and 85 per cent relative humidity,” said Wouter Gabrielse, automotive segment manager for DSM. “Parts made from Arnite A HR keep around 90 per cent of their initial strength under the same conditions. The performance we have achieved is spectacular.” Arnite A HR can replace metals or
higher cost engineering plastics such as polyphthalamide (PPA) and polyphenylene sulphide (PPS) in parts that require high dimensional accuracy, and good chemical resistance and mechanical properties.
www.engineerlive.com 7
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