Plastic composite makes sunroofs safer

Edited by the Engineeringtalk editorial team Mar 7, 2006

Plastic composite for vehicle sunroofs provides up to eight times the impact performance and weighs up to 30% less than pure organic plastic glazing or other glass-glass laminates.

DuPont has introduced Spallshield, a plastic composite product for use in vehicle sunroofs.

It is an alternative to pure organic plastic glazing or other existing glass-glass type laminates.

Applied to a single layer of glass, Spallshield provides up to eight times the impact performance versus standard laminated glass, while weighing up to 30% less.

The technology was used in new cars from Mercedes-Benz during the second half of 2005.

The market for sunroofs in vehicles is experiencing constant and steady growth of about 10 to 15% a year.

At the same, driver requirements for increased daylight and space perception within the vehicle are driving the development of larger, so-called panoramic sunroofs - in some cases constituting over 1m2 of glass fitted within the roof.

However, as sunroofs grow in size, so do concerns primarily around safety - the disintegration of the glass in the event of an impact and the potential ejection of passengers - and weight.

Until present, existing sunroof glass technologies have been based around the use of either tempered glass or standard laminated glass.

Single-layer tempered glass, the traditional, lower-cost material alternative, is viewed as relatively heavy for larger sunroofs, and represents a potential danger for passengers in the event of an impact.

Greater impact resistance is provided by standard laminated glass, whereby an interlayer of polyvinyl butyral film (PVB) is sandwiched between two sheets of glass, although weight, resulting from its dual glass-layer composition, remains an issue.

DuPont has combined the positive attributes of plastic, laminated and tempered glass.

Spallshield is a composite of PVB and polyethylene terephthalate (PET), with an additional anti-scratch coating on the PET, which can be applied to a single, standard layer of glass using traditional glass lamination processes.

It provides all the benefits of standard laminated glass, such as weathering, scratch and chemical resistance, yet is up to eight times stronger and 25 to 30% lighter than laminated glass.

In addition, the plastic composite protects against spalling, should the glass be broken.

The PET film, laminated with the glass, serves as a spall protection layer or shield, which keeps the dangerous glass shards in place until replacement of the part.

Standard laminated glass, which has an unshielded layer of glass facing towards the interior of the vehicle, or traditional tempered glass, cannot provide the same protection.

In fact, because of its anti-spalling features, Spallshield plastic composites have been used in bullet-resistant and hurricane glass applications for the past 25 years.

Hayati Yarkadas, Global Marketing Manager for DuPont, said: "The automotive industry has been looking for glazing that combines the positive attributes of plastic and glass".

"DuPont Spallshield enables this marriage".

"Glass provides the stiffness and mechanical strength, while Spallshield increases impact performance, both outwards and inwards, and eliminates the need for a second layer of glass, thus reducing overall weight".

Spallshield made its global market premiere in sunroof systems incorporated in the S and R Class models from Mercedes-Benz, launched during the second half of 2005.

At the same time, the technology is being considered for use on some 14 other vehicles.

Beyond existing sunroof applications, it is also being considered for sidelights and backlights.