Effective June 2015, certain quarter windows made of plastic are exempted from a previous regulation that set stringent requirements in terms of scratch resistance that necessitated application of a protective coating. This recent amendment of the ECE R43 standard should deliver opportunities for acrylic resin according to supplier Evonik and offer designers exciting new creative scope.
|Small quarter windows can now be made from uncoated acrylic resin.|
Evonik states that its Plexiglas is an ideal material for these panels because the highly transparent PMMA material offers the highest surface hardness of all thermoplastics, even without coating. At the same time, the small quarter windows offer a host of design options for curved lines and striking edges that cannot be realized with glass: "Plexiglas can be injection molded into almost any imaginable 3D shape," says Uwe Löffler, director Business Development Automotive at Acrylic Polymers in the Evonik Performance Materials Segment. "Panels can be produced with built-in wind deflectors and sharp angles. And the panels can be wraparound," Löffler adds.
The new exceptions relate to all windows made of plastic that do not affect the driver's view and whose surface area must be of a size whereby a circle of 150 mm diameter does not fit inside its dimensions. The overall panel size must not exceed 200 cm2. One example is the small quarter window behind the C pillar that is being used as a design element by a growing number of manufacturers. In principle, other small quarter windows are also conceivable as long as they meet the given criteria.
Although PMMA has the highest surface hardness of all thermoplastics, it does require a scratch-resistant coating for safety-relevant rear and side windows. "But the new exceptions to the regulation make Plexiglas the material of choice especially for these small quarter windows," Löffler says. Added to the design benefits, there are the favorable costs. Based on the new regulation, Plexiglas requires no additional coating for manufacturing a small panel. This is because, unlike other transparent thermoplastics, the material is inherently resistant to UV light and weathering, and the panels can therefore be manufactured in a single step.