Delamination Issues with Laminated Glass – Causes and Prevention

Despite the long history of the use of laminated glass in buildings there is concern with some architects on the potential for serious delamination issues with laminated glass. This paper provides test data on the edge stability of laminated glass and details various types of delamination problems, which can arise if proper glass processing and installation practices are not followed. Guidance is also given on how to avoid such problems. Types of Delamination Delamination issues with laminated glass made using PVB interlayers fall into two main categories: • Sunburst delaminations • Edge delamination ‘Sunburst’ Delaminations ‘Sunburst’ delaminations (see Figure 1) in some projects have undoubtedly caused concern in the glazing industry. This type of delamination is generally the result of poor manufacturing processes, which impart stresses at locations at the edges of laminated glass, often combined with thinning of the PVB. Optical distortion is also normally evident at these locations. The most common cause of this type of localized delamination is the use of clamping devices on the edges of laminated tempered glass during the autoclaving of the laminated glass. While the quality of the glass may appear to be satisfactory at time of dispatch of the glass from the factory gradual release over time of the stresses imparted to the glass at the locations that were clamped may result in ‘sunburst’ delaminations. As detailed by Jorma Vitkala in his Glass Processing Days 1999 paper, ‘Low-E Tempering The Latest Results’ with laminated tempered or heat strengthened glass special attention needs to paid to the glass quality in relation to fl atness and edge-curving. “If any glass is heated unevenly in the tempering process there is a tendency for the edges of the glass to curl and this is especially the case with pyrolytic Low-E coated glass”. Laminated glass for point fi xed applications such as canopies or frameless façade glazing requires special processing to prevent thinning of PVB around the holes in the corners of the laminates. Unless precautions are taken thinning of the PVB around holes may occur due to PVB fl ow in the autoclave process. Such thinning may result in the formation of bubbles or delamination around the holes following installation of the glass.