New Xantar and Arnite Grades from DSM Engineering Plastics

25 June 2004

DSM Engineering Plastics have developed two materials for use in and around the headlamp of the 2003 model Audi A3.

This was produced in close collaboration with Automotive Lighting GmbH and Coko Werke. In developing the styling for this headlamp, Audi decided to specify the use of plastic parts where the appearance does not need to be enhanced by after treatments like painting or chrome plating. The biggest challenge was to achieve an exact colour match of the metallic grey in two adjacent parts made from intrinsically different polymers.

DSM’s Arnite TV4 220 polybutadiene-terephthalate (PBT) resin was selected for the parts that are in close contact to the headlamp and must resist temperatures up to 160°C, as well as exhibit low weld line visibility. Arnite TV4 220 is a 10-percent glass-fibre-reinforced PBT grade with low outgassing and a heat deflection temperature (HDT) of 180°C. Xantar RX 1045 polycarbonate (PC) resin was chosen for the frame that is located directly behind the headlamp glass. This part needs to be absolutely flat, and due to its close proximity to the headlamp lens, requires excellent surface aesthetics. Xantar RX 1045 is a low-warpage, low-outgassing, high-flow PC resin developed by DSM Engineering Plastics especially for metallic colours.

“The new materials were engineered to meet Audi’s stringent exterior trim and lighting specifications for its A3 headlamp,” said DSM’s Bert Gebbing, Application Development Manager for Xantar. “Audi wanted materials for this application that provided excellent Class A appearance without after treatment like painting or chrome-plating.”

According to Richard Frissen, Application Development Manager for Automotive Lighting GmbH, “DSM’s Arnite and Xantar teams worked together to solve the challenge of colour matching a metallic gray colour in two adjacent parts using a new combination of Xantar PC and Arnite PBT resins. The result of the collaboration is an ultra-sleek, ultra high-tech look for Audi’s headlamp that is built to retain its good appearance for years.”

Designed for intrinsic coloured bezel mouldings, Arnite TV4 220 is a 10-percent glass-fibre-reinforced PBT that provides high strength and stiffness, heat resistance – an HDT of 180°C – combined with resistance to outgassing at high temperatures and excellent dimensional stability. Arnite TV4 220 shows excellent surface qualities in moulding, low weld line visibility, and accepts most polymer colourants, additives and fillers. It exhibits outstanding electrical properties and low water absorption. Finally, because it is highly resistant to creep and has good mould flow properties, Arnite TV4 220 allows designers great freedom for bezel designs or mouldings with thin wall sections, deep ribs, mounting tabs, and other highly defined geometric part attributes. The material favours fast injection rates and excellent demoulding.

Xantar RX 1045, designed especially for metallic colours, provides a high-strength material with excellent aesthetic properties and short cycle times, ideal for headlamp assembly lens frames and other trim or housing components. The new Xantar grade is a low-warpage, low-outgassing, high-flow PC resin. High impact and stress crack resistance provide protection against the day-to-day onslaughts commonly experienced by automotive exteriors. Xantar RX 1045 is also resistant to hydrocarbons and salts.

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