Volume 7, Issue 5, September-October 2003
Structural Silicone Sealant for
Safety and Security Film Attachments
As we see increased awareness concerning the use of safety/security films for a number of applications dealing with glass hazard protection from hurricanes and tornadoes, criminal trespass and bomb blasts, the film industry has developed ways to help increase the capacity of a window opening with film attachments. These methods have been employed to help keep the film and glass in the frame or window opening after the glass has failed as a result of one of the aforementioned events. A method frequently used is a structural silicone sealant manufactured by either Dow Corning or GE Sealants, combined with a fragment retention window film.
All Systems Are Not Created Equal
Each of the applications to which I refer above have slightly different requirements, therefore any system used needs to be evaluated for the specific need and must only be used as tested. For example, a system that passes a 4-pounds-per-square-inch (psi) blast load test may not be applicable for a windstorm (hurricane) application. Performance depends upon the strength of the entire glazing system (including film, sealant and frame). For this discussion, we’ll use the U.S. General Services Administration’s (GSA) criteria for a 4-psi medium-to-low level bomb blasts.
A series of blast tests were performed last year by the GSA for development of a quality assurance standard for a structural wet-glazed film system that will be incorporated into the Glass Hazard Mitigation Program for Federal facilities. One of the issues GSA has to deal with is what constitutes a structural wet-glaze as opposed to standard wet-glaze (or what is sometimes referred to as a “beauty-bead” application). Results for these tests can be found on the GSA website www.oca.gsa.gov.
Figure 1 below illustrates a method GSA currently has required for current scopes of work (SOW).
The Protective Glazing Council’s website is an excellent resource for a downloadable white paper by Dow Corning on the use of a structural sealant with film.
Please visit www.protectiveglazing.org/references/index.html to obtain your copy.
Figure 2 illustrates the correct method from Dow Corning’s white paper.
Both methods illustrated employ a significant sealant bite onto the filmed glass and frame. To assure sealant adhesion for a blast and/or high performance application, a minimum ˝-inch bite is required with a triangular sealant joint. It is important to note that sealing with an existing gasket in place is not recommended since sealants often do not adhere to gasket material and, additionally, the gasket my not be designed to support the given load.
The above is a guideline and discusses only one of the components of a window system. The entire system needs to be evaluated by an acknowledged professional who can recommend the proper glass hazard mitigation upgrade.
This information is adapted from an article in the IWFA Summer 2003 newsletter, with permission.
Scott Haddock is president of the Protective Glazing Council (PGC) and GlassLock of San Jose, Calif.
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