Laminated safety glass with DuPont™ SentryGlas® interlayer shows no sign of aging after five years

Laminated safety glass with high strength, high stiffness DuPont™ SentryGlas® interlayer shows no significant signs of aging despite five years of exposure to the rough climate of northern Germany. This was the expert opinion of the independent consulting engineers Kallinich o.b. u. v. HK Hamburg, who – as part of a predetermined long-term inspection – removed ten panels from the glass facade of the administrative headquarters of Deutscher Ring Lebensversicherungs-AG in Hamburg and replaced them with reserve panels set aside for such circumstances. Comprehensive tests were carried out on the removed panels, the results of which were compared with data recorded with new panels.

“After five years of use and almost constant exposure to water spray, we found no sign of hazing, delamination or edge defects on any of the panels, not even at their edges,” comments the surveyor Dietmar Kallinich. “Flexural load testing, carried out at the high wind loads typical for buildings in such a location, revealed the same low rate of deflection we would expect to achieve with brand new panels. This indicates that the special ability of SentryGlas® interlayer to transfer shear loads, for even greater safety, is retained despite its long-term exposure to these particularly demanding conditions. The post-breakage strength of the laminated glass panels – a very important factor in terms of the safety of passers-by – remains consistently high.”

An almost perfect transmission of load
An important criterion for the use of laminated glass in facade applications is the no-sag behavior of the interlayer when exposed to moisture. The SentryGlas® interlayer is non-hydroscopic and, in comparison to standard PVB interlayers, is over 100 times stiffer and five times stronger. This means that there is an almost perfect transmission of load between the laminated plies of glass. As a consequence, laminates with SentryGlas® exhibit less than half the rate of deflection of comparable laminates made with standard PVB interlayer under the same load, behavior that is close to that of monolithic glass panels of the same thickness. These properties remain largely the same and stable over a temperature range of between–15 °C and +50 °C. It is on the basis of these properties, and following comprehensive testing, that the Deutscher Ring project gained the building authority approval they required – at that time only granted on a case-by-case basis – for the use of laminated safety glass with SentryGlas® interlayer. A mandatory inspection of the laminated glass after 5 and 10 years respectively formed part of this approval.

This regulatory approval enable the continued use of the existing support structure, made from aluminum fittings, that had been designed for use with toughened safety glass panels with a thickness of up to 12 mm. The only requirement was a redesign of the mounting brackets. The common alternative to toughened safety glass at the time, a laminate with standard polyvinyl butyral (PVB) that is unable to transfer such high shear loads, would have been too heavy for the existing support structure. Instead, the operating company for the building was able to cost-efficiently gain a significant improvement in safety with its “lightweight” glazing solution consisting of two plies of 6 mm heat-strengthened glass and a 1.52 mm interlayer. Post-breakage strength of the laminate is increased, with the panels remaining securely intact within their fixings.

Additional benefits for budgets and the environment
In 2009 laminated safety glass with SentryGlas® interlayer received general approval for use in construction in Germany. This means that architectural glazing produced with this material involves no additional bureaucratic expense, thereby vastly extending its potential for use. Today, laminated safety glass with SentryGlas® is used for architectural projects around the world such as glazed balustrades, flooring, stairways and pedestrian bridges. Its adoption helps reduce transportation costs too, due to the fact that a laminated glass panel with SentryGlas® interlayer is approximately one third thinner and lighter than a panel of the same performance made with a PVB interlayer. Moreover, it is often the case that glass construction companies are able to use standard lifting equipment when handling laminated safety glass with SentryGlas®, whereas heavy panels with a PVB interlayer may well require the services of a specialized company.

DuPont Glass Laminating Solutions provides manufacturers and the specifiers of laminated glass access to materials, services, and innovative processes which contribute to a better world. Buildings are better protected, vehicles made safer, and constructions are more stable and energy efficient with more natural light being introduced into them.

DuPont (NYSE: DD) has been bringing world-class science and engineering to the global marketplace in the form of innovative products, materials, and services since 1802. The company believes that by collaborating with customers, governments, NGOs, and thought leaders we can help find solutions to such global challenges as providing enough healthy food for people everywhere, decreasing dependence on fossil fuels, and protecting life and the environment.

The DuPont Oval, DuPont™ and SentryGlas® are registered trademarks or trademarks of E. I. du Pont de Nemours and Company or its affiliates.

Note to the editor:
This press release is based on information provided by:
Ingenieurbüro Kallinich IBK
Waldweg 18, 22393 Hamburg, Germany
Telephone: +49 (0) 40 6 02 48 43
E-Mail: info@kallinich-ibk.de
Contact: Dietmar Kallinich
www.kallinich-ibk.de
Editorial contact:
Birgit Radlinger
Tel.: +49 (0)6102 18-2638
Email: Birgit.Radlinger@dupont.com