Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass. In the case of the EVA, the thermoset EVA, offers a complete bounding (cross-linking) with the material whether it is glass, polycarbonate, PET, or other types of products.
Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered and also for architectural applications. Skylight glazing and automobile windshields typically use laminated glass. In geographical areas requiring hurricane-resistant construction, laminated glass is often used in exterior storefronts, curtain walls and windows.
Laminated glass is also used to increase the sound insulation rating of a window, where it significantly improves sound attenuation compared to monolithic glass panes of the same thickness. For this purpose a special "acoustic PVB" compound is used for the interlayer. In the case of the EVA material, no additional acoustic material is required, since the EVA provides sound insulation.
An additional property of laminated glass for windows is that a PVB and EVA interlayer can block essentially most ultraviolet radiation. A thermoset EVA could block up to 99.9% of all UV rays.
Newer developments have increased the thermoplastic family for the lamination of glass. Beside PVB, important thermoplastic glass lamination materials today are ethylene-vinyl acetate (EVA), thermoset EVA ethylene-vinyl acetate (EVA) and thermoplastic polyurethane (TPU). The adhesion of PVB/TPU and EVA is not only high to glass, but also to polyester (PE) interlayers. Since 2004, metallised and electroconductive polyethylene terephthalate (PET) interlayers are used as substrate for light emitting diodes and laminated to or between glass. Coloured interlayers can be added to provide a permanent transparent colour for a laminated glass panel. A switchable interlayer can also be added to create a panel which can be clear when a small electric current is passed through the interlayer and opaque when the current is switched off. This is commonly known as privacy glass.
Parameters For Laminated Glass: