Laminated glass
Laminated safety glass (LSG ) owes its safety properties of a tear-resistant and tough elastic film between the glass panes. By means of a roller press foil is a so-called " pre-bond " of two or more superposed glass sheets and usually a polyvinyl butyral (PVB) or ethylene vinyl acetate ( EVA) existing prepared. Then under heat (about 140 degrees) and pressure a permanent bond of glass and foil in the autoclave is created (about 12 bar).
Characterized in case of breakage it binds splinter and thus causes a considerable reduction of the risk of injury. The film also makes it difficult to penetrate the glass: VSG is the basis for an intrusion protection. When using sufficient thicknesses of films and glass, armored glass is made.
Another advantage of VSG over conventional glass is its ' residual capacity '. Even after partial destruction of the glass still has a certain protective effect. VSG is therefore used when the opening in the event of a claim is to remain closed, or when a falling shards must be avoided around. For this purpose VSG of two (or more) TVGS ( semi-tempered glass) is made more frequently. In the event of destruction of the VSG then the opening keeps closed and does not sag - as on the picture to see - in together.
The windshields of automobiles ("Auto Glass " ) are made of laminated safety glass, thus protecting the occupants in the event of damage from flying shards of glass and on the plate striking objects. In some models, the upper and middle class VSG is also used for side and rear windows. In addition, VSG is among other things used in schools, kindergartens, swimming baths, in the living area, with secured against falling glass ( parapets ) or for overhead glazing (for example, in conservatories ).
VSG has a damping effect on sound. For example, a glass of the composition is from 3 mm foil 3 mm is less excited to vibrate as a disc of 6 mm thick glass, - the film attenuates the vibrations. There are also extra soft sheet or sheets with a soft core that are specifically tailored to sound attenuation for this purpose. There are films of different thickness (for example, 0.38 mm and 0.76 mm). The thicker the film / slides - glass combination, the more it inhibits throws, shots and pressure waves. There are also films that matte (instead of transparent) or colored. In addition to the VSG with films, there are also laminated glass (VG ) without security features.
As described above, the lamination is achieved by means of the above-mentioned PVB (polyvinyl butyral) as a connecting thermoplastic two sub-processes: in the nip roller, a weakly heated pre-laminate (about 65 ° C) is prepared in which the majority of air bubbles are rolled out. The discs come in the autoclave, where customarily generate 12 bar and 140 ° C the final composite. The six - figure investments for autoclaves are rarely financially viable for smaller companies. Therefore smaller VSG manufacturers also use a autoklavenfreien process with PVB or EVA ethylene vinyl acetate or plastic TPU ( thermoplastic elastomers), which can be small vacuum Thermoöfen that there are already over 15 000 Euro, respectively. Adhesion of TPU and EVA is compared with additional intermediate layers such as polycarbonates, dichroic films or polyester films LED, higher than PVB, which reduces the risk of subsequent delamination or microcracks (due to plasticizer migration ).
Quality assurance
To check the quality of laminated safety glass are used, inter alia, the so-called pummel, the ball drop test and the Baketest.
The pummel ( from the English language to pummel = beat ) shows by hammering a VSGs at minus 18 ° C, how many pieces of glass sticking in case of breakage of the wheel to the incorporated film or how many dissolve and thus pose a risk of injury.