Laminated glass and laminated safety glass
Laminated glass consists of two or more glass layers, which are interconnected with one or more elastic intermediate layers. Laminated glass is produced and marked in accordance with the European Construction Products Regulation. The product properties and specification requirements are defined in DIN EN ISO 12543-1 to 12543-6. The factory production control and appropriate product labelling must be carried out in accordance with DIN EN ISO 14449.
The majority of industrially produced laminated safety glass in Europe is processed with a polyvinyl butyral (PVB) film as an intermediate layer.
For this, the glass panes to be laminated are superimposed with the film as an intermediate layer. Subsequently, the panes are pressed together in press rollers at about 80° C with each other. The panes are still cloudy at this time to see through and lack the necessary adhesion between the glass and the composite film. Only in an autoclave at a pressure of 13 bar and a temperature of 130° Celsius the full adhesion between the surfaces is developed. The duration of the panes in the autoclave depends on the glass thicknesses and the number of glass panes to be laminated.
In rare cases, a thermoplastic (ionoplast) is used as an intermediate layer. This intermediate layer is usually processed in a composite bag. Glass with the ionoplastic interlayers are sealed in a vacuum bag. Subsequently, air is evacuated from the vacuum bag. In the autoclave at about 13 bar and 120° C the adhesion between the glass and the composite film is established.
The production of laminated glass products with Ethylene Vinyl Acetate Foils or cast resin interlayers is hardly relevant industrially.
The properties of composite and laminated safety glass are diverse, but they change with the use of different materials. Accordingly, the ionoplastic interlayer is known for improving structural rigidity and remaining structural capacity. It is usually used there when there are increased structural requirements.
In order to increase the sound insulation, softer, specially developed PVB films are used.
There is also laminated glass, which serves to increase fire protection due to its swelling intermediate layers.
Laminated glass, with particularly tear resistant foils, are used for knock-through, breakthrough, bullet penetration and explosion resistant glazing.
By using coloured foils or laminating additional materials, laminated glass can be adapted to architectural requirements.
Due to widespread and standardised processing methods, the visual quality of laminated glass is generally very good. Only in rare cases are inclusions or optical distortions visible.
Far more frequently objected to are the so-called “delaminations”. In the case of delaminations the adhesion between the composite foil and the glass surface is missing. This can be seen in the form of bubbles between the glass panes. This may be due to a chemical incompatibility with adjacent building materials, an error of application or defective product quality. In most cases, several factors are critical to failure. Only rarely do delaminations have no immediate effect on the safety properties of the glass.
Laminated safety glass is usually used where additional safety requirements have to be fulfilled. As the fall safeguarding of balconies, laminated safety glass serves as the direct protection of a person. In overhead applications, the use of laminated safety glass ensures that, in the case of glass breakage, no large glass elements fall on traffic areas below. To minimise the effects of explosions, explosion resistant glazing is also being installed in a growing number of construction projects.
The use of rigid composite films and multiple laminates are increasingly built in structurally load bearing glass elements. Examples of these include: Glass beams of glass columns. Also load bearing glass walls are installed in modern architecture.