Laminated safety glass
Laminated safety glass ( VSG ), also laminated glass or rarely laminated safety glass, provides a composite of two or more flat glass sheets joined by a tear-resistant and tough elastic film. It has several security features (puncture-resistant, much lower risk of injury from splinters) compared to a simple flat glass plate and a significantly higher sound insulation. It was available as Sigla multilayer glass by the mid-1930s at the latest.
Manufacturing
Laminated safety glass owes its safety properties to a tear-resistant and tough elastic film between the panes of glass. Using a roller press, a so-called “pre-bond” is produced from two or more glass panes lying on top of one another and a film usually made of polyvinyl butyral (PVB) or ethylene vinyl acetate (EVA). The autoclave is subsequently (about 140 ° C) (about 12 bar) pressure created and a permanent bond of glass and foil under heat.
As described above, the lamination using the above-mentioned PVB as a connecting thermoplastic is achieved via two sub-processes: In the roller pre- lamination process, a slightly heated pre-lamination (approx. 65 ° C) is produced, in which most of the air inclusions are rolled out. The panes are then placed in the autoclave , where 12 bar and 140 ° C usually generate the final bond. The 6-digit investments for autoclaves are seldom affordable for smaller companies. Smaller laminated safety glass manufacturers therefore also use an autoclave-free process with PVB (after the film has been dried at approx. 10% relative humidity) or the plastics EVA, ethylene vinyl acetate or TPU ( thermoplastic elastomers ), which use small vacuum thermo-ovens that remove it 15,000 euros can be connected. The adhesion of TPU and EVA to additional intermediate layers such as polycarbonates, dichroic foils or polyester LED foils is higher than that of PVB, which reduces the risk of later delamination or microcracks (due to plasticizer migration).
properties
Laminated safety glass binds splinters in the event of a break, thereby significantly reducing the risk of injury. The film also makes it difficult to penetrate the glass: Laminated safety glass is the basis for burglary protection . When using sufficient thicknesses of foils and glass, bulletproof glass is also created .
Another advantage of laminated safety glass over conventional glass is its 'residual load-bearing capacity'. Even after partial destruction, the glass still has a certain protective effect. Laminated safety glass is therefore used if the opening should remain closed in the event of damage or if, for example, broken fragments must be avoided. For this purpose, laminated safety glass is increasingly being made from two (or more) TVGs ( partially toughened glass ). In the event of destruction, the laminated safety glass then keeps the opening closed and does not collapse - as can be seen in the picture.
The windshields of automobiles ( " Auto Glass ") are made of laminated safety glass, protecting the occupants in the event of damage from flying glass shards and the disc striking objects. Laminated safety glass is also used for the side and rear windows on some models in the upper and middle class. Laminated safety glass is also used in schools, kindergartens, indoor swimming pools, in living areas, for glass to protect against falls ( parapets ) or for overhead glazing (for example in winter gardens).
VSG has a soundproofing effect. For example, a pane of glass with the composition 3 mm + film + 3 mm is less stimulated to vibrate than a pane of 6 mm thick glass - the film dampens the vibrations. For this purpose there is also extra-soft foil or foils with a soft core, which are specially tailored for soundproofing. There are foils of different thicknesses (for example 0.38 mm and 0.76 mm). The thicker the film / film-glass combination, the more it inhibits throws, shots and pressure waves. There are also foils that are matt (instead of transparent) or colored. In addition to laminated safety glass with foils, there are also laminated glass panes (VG) without security properties.
Heating and antenna systems can also be integrated into the foils used as intermediate layers.
Notation
Laminated safety glass is written as two numbers between 2 and 19, followed by a period and a third number, usually between 1 and 6.
- The first digit is the slice thickness of the first slice in millimeters
- The second digit is the thickness of the second disk in millimeters
- The third digit is the thickness of the foil in 0.015 inches (1: 0.38 mm; 2: 0.76 mm; ...)
Examples:
- VSG 33.1: 3 mm pane + 0.38 mm film + 3 mm pane
- VSG 44.1: 4 mm pane + 0.38 mm film + 4 mm pane
- VSG 86.2: 8 mm pane + 0.76 mm film + 6 mm pane
- VSG 1212.4: 12 mm pane + 1.52 mm film + 12 mm pane
Other spelling (e.g. common in Great Britain), examples:
- 6.4 = 2 × 3 mm glass and 0.4 (0.38) mm foil
- 8.8 = 2 × 4 mm glass and 0.8 (0.76) mm foil
- 11.5 = 2 × 5 mm glass and 1.5 (1.52) mm foil
- 12.8 = 2 × 6 mm glass and 0.8 (0.76) mm foil
- 13.5 = 2 × 6 mm glass and 1.5 (1.52) mm foil
quality control
The so-called pummel test, the ball drop test and the bake test are used to control the quality of laminated safety glass.
The pummel test (from the English to pummel = to hit ) shows by hammering a laminated safety glass at minus 18 ° C how many pieces of glass will stick to the incorporated film or how many will loosen and thus represent a risk of injury if the pane breaks.
Heating and antenna integration
The film serving as an intermediate layer can also be used to integrate functions into the laminated safety glass.
For example, very thin tungsten wires (diameter in the range 16–40 µm) can be applied to this film and used as resistive glass heating. This heating function is mainly used in the automotive industry (often: front windows and more rarely: rear windows). Other industries are aircraft glass (cockpit), train glazing (cockpit), architectural glass (roofs), military glazing.
Copper wires (diameter in the range 50–100 µm) can also be embedded, which are used as antennas. This antenna function is mainly used in the automotive industry (front windows)
See also
literature
- Design with glass . 7th revised edition. Interpane Glas Industrie AG, p. 157
- Glass construction practice, construction and dimensioning . 2nd Edition. Publishing house Bauwerk, Weller / Nicklisch / Thieme / Weimar 2010.
Web links
Individual evidence
- ↑ The glass car. In: Österreichischer Motor / Europa Motor , issue 5/1935, p. 8 (online at ANNO ).
- ↑ Electronic components in glass laminates . (PDF; 1.8 MB) In: Glass Architecture and Technology , 2007.