When it comes to overhead glass, architects are often limited by the need to use laminated safety glass. However, Sika's innovative laminated composite opens a whole world of design freedom.
For glass in overhead applications such as canopies, laminated safety glass is usually specified. This type of glass is fixed either with visually disturbing multipoint metal fasteners or a continuous edge support with a massive metal profile. Both strongly undermine the architect's vision of an elegant glass surface.
Therefore Sika and sedak have jointly developed a novel laminated composite comprising a monolithic glass panel, a layer of Sikasil GS-687 self-levelling silicone adhesive and a load-transferring perforated aluminium panel. With the laminar silicone application, the use of opaque glass in overhead situations, as well as in vertical details, is feasible without any visible mechanical fixings.
An essential aspect of glass bonding is the post-breakage behaviour of PVB-laminated safety glass. The mechanical performance of the PVB interlayer is diminished above 30°C and under long-term loading. Therefore the residual strength of PVB-laminated glass is rather limited at elevated temperatures.
As mechanical and adhesion properties of silicone are almost unchanged from -40 to +150°C, laminar-bonded panels show excellent post-breakage behaviour. To prove the long-term resistance, Sikasil GS-687 was tested by independent laboratories complying with ASTM C1184, ASTM C920 and ETAG002.
An additional advantage is the remarkable weight reduction. In a recent US project with more than 60,000m2 of glass canopies, the planned 14.3×3.2m PVB-laminated safety glass panels made of 2×12mm fully tempered glass panes have been replaced by laminar compositions comprising a 10mm heat-strengthened glass pane, a 6mm silicone layer and a 3mm aluminium sheet, saving 30% of total weight.
Altogether, the aesthetic, along with the convincing technical advantages, make laminar glass bonding a versatile technology for architectural glass fixations. It gives architects freedom of design - whether that be for a huge opaque canopy, the undisturbed vertical glass wall or the glossy appearance of a glass spandrel panel.