Windows: Breaking the Glass Barrier

Recent advances in materials and processing technology have for the first time made polycarbonate a viable alternative to glass for mass-produced vehicles.

With its optical clarity and high impact properties, polycarbonate has drawn interest as an automotive glazing candidate for years. And the material has already seen limited use in production vehicles--notably in the SMART car's wraparound quarter windows. Until now though the plastic hasn't gone beyond what could generously be described as niche applications. Blame the auto industry's valid concerns about cost and some skepticism that polycarbonate can meet performance standards. In June, Exatec LLC, a Wixom, MI-based technology company formed by polycarbonate suppliers Bayer Polymers and GE Plastics, launched a proprietary materials and manufacturing system that could overcome those concerns.

The system addresses the technical limitations associated with plastics--including its sensitivity to UV light and its soft surface relative to glass. It could also parlay other aspects of injection-molded plastics into an advantage over glass as well. Chief among these are new styling possibilities that spring from plastics' design freedom. "Styling will be the main driver for polycarbonate," predicts Exatec manager Peter Reisinger. "So much of what cars look like today are related to the limitations of glass glazing," he continues, citing the constraints imposed by glass's relative flat geometries, limited color pallet, and decoration shortcomings. Polycarbonate also promises to aid other important engineering endeavors, including weight reduction and safety enhancement. And properly designed polycarbonate windows even offer the potential for function integration and parts consolidation.

Despite these potential advances, don't look for polycarbonate to overtake glass anytime soon for a couple of reasons. For one, glass gets better all the time. For another, current NHTSA safety regulations rule out plastic for windshields as well as for moveable side windows. "That leaves just the fixed vent window and back lights," says Paul Eichenberg, marketing manager for PPG Industries' North American glass business (www.ppg.com) in Troy, MI. And though regulations can always change to keep pace with new technology, Exatec itself has no current plans to tackle the windshield. "It will be the last area we target," Reisinger admits.

Even if some windows remain off limits for now, there are still plenty of places where polycarbonate glazing could add value. Panoramic roofs, increasingly common in Europe and making their way here, are a good fit. "It's where our weight and safety advantages matter the most," Reisinger says. He adds that Exatec's technology, despite its recent launch, has already garnered strong interest from OEMs and suppliers.