The lamination of glass debate
Despite the recent surge in interest in development and use of laminated glass, be it manufactured using foils or liquid composites, laminated glass itself is not a new invention, as Chris Davis, composites manager at Kommerling, explains.
The first laminated glass was, like so many inventions and discoveries, an accident; working in his laboratory in 1903, French chemist Edouard Benedictus dropped a glass flask that had been inadvertently coated with cellulose nitrate (a plastic like substance).
While the glass shattered, the pieces were not scattered across the floor. It was several years until he registered his patent but laminated glass had been born and its benefits were instantly recognised; it was used in the eye pieces of gas marks in the first world war and become a legal requirement in the UK for car windscreens as early as 1930.
Towards the end of the 20th century, bespoke foils were often the preferred means of producing laminated glass. However, more recent developments in glass manufacturing technology and capabilities means that laminates formed using liquid composites are becoming increasingly widespread. Not least as the composite can enhance and extend the inherent capabilities of the glass without compromising on its clarity.
One of the key benefits of using a liquid composite comes down to the molecular changes that take place during the manufacturing process. The presence of cross-linked polymers that are formed as the composite cools and shrinks within the unit makes for bonds with better sheer, creep and relaxation properties than is generally found with foils, which ultimately enhances its continued mechanical performances, particularly as temperatures change.
Having first washed and prepared the glass, the next stage is to apply a continuous edge barrier along the sides of the unit, leaving just a small gap for filling. The glass panels are brought together and pressed together to form an envelope, which is held in the vertical as the correct volume of liquid composite is dispensed into the gap.
Anywhere between 2%-13% extra composite over the calculated volume of the unit will be applied to accommodate for the shrinkage that takes place during the curing process and resulting from the cross linking. Any excess air must then be removed and the unit securely sealed.
Curing may take place under UV lights (minimum 15 minutes) or the longer, catalytic process, which can take from three to 48 hours, dependant on the materials.
Comparing the two approaches – foil or liquid composite – is complex as there are so many variables, eg, the specific foil or composite being applied, the thickness of the glass, the curing process etc. It is interesting to examine the benefit of lower post cure failure rates and fast curing cycles evident with the passive curing profile synonymous with catalytic and UV curing systems
More and more liquid composites are being introduced in the commodity laminate market, offering benefits in terms of curing speed, improved production capacity, and new add attributes such as UV protection and acoustic management. In addition, new structural, media glass where the LEDs and associated circuitry are located within the sealed unit, mean that that the composite must have no conductive properties or this would absorb the current and interfere with the LED circuitry and ultimately the glass’s media capability.
Architects, and consequently glass and facade engineers, are constantly pushing the boundaries and demanding that glass that delivers far more than just a clear view into the outside world. Laminating panels of glass with different performance criteria and adding an additional feature to the interlayer itself all help to make these new specifications possible.
There will always be a role for foils but as our expectations of buildings, their performance and the materials from which they are constructed, continue to expand then the role of the liquid composite is one that is only going to increase.