User:Taylorrnguyenn/Laminated glass

Lead
Laminated glass (LG) is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by a thin polymer interlayer, typically of polyvinyl butyral (PVB), Ethylene Vinyl Acetate (Cross-Linked EVA), lonoplast Polymers, Cast in Place (CIP) liquid resin, or Thermoplastic polyurethane (TPU), between its two or more layers of glass. The interlayer, made through heat and pressure, 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. The thermoset EVA offers a complete bonding (cross-linking) with the material whether it is glass, polycarbonate, PC, or other types of products.

Laminated glass is used for architecture, glazing, automobile safety, photovoltaic, UV protection, and artistic applications. The most common use of laminated glass is skylight glazing and automobile windshields. 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, because 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. TPU is an elastic material, so sound absorption is intrinsic to its nature. An additional property of laminated glass for windows is that an adequate TPU, PVB or EVA interlayer can block nearly all ultraviolet radiation. A thermoset EVA, for example, can block up to 99.9% of all UV rays.

Article body - Specifications
A typical laminated makeup is 2.5 mm glass, 0.38 mm interlayer, and 2.5 mm glass. This gives a final product that would be referred to as 5.38 laminated glass.

Strength can be increased in laminated glass with multiple laminates and thicker glass. Bullet-resistant glass is usually constructed using polycarbonate, thermoplastic materials, thermoset EVA, and layers of laminated glass.[citation needed] A similar glass is often used in airliners on the front and side cockpit windows, often three plies of 4 mm toughened glass with 2.6 mm thick PVB between them.[citation needed] This is one of the makeups used for the Boeing 747 cockpit side windows.[citation needed] The BAC/SAF Concorde forward pressure windshields had 7 plies, 4 glass and 3 PVB total thickness 38 mm.[citation needed] For increasing sound attenuation through laminated glass for extreme sound levels, using a mix of 3 mm, 4 mm, 5 mm, and 6 mm glass thickness would be more effective.

Article body - Production
Modern laminated glass is produced by bonding two or more layers of ordinary annealed or tempered glass together with a plastic interlayer, usually polyvinyl butyral (PVB), Thermoplastic polyurethane (TPU), or Ethylene Vinyl Acetate (Cross-Linked EVA). The interlayer is meant to improve mechanical properties such as impact strength, fracture toughness, and failure modes in laminated glass. The plastic interlayer is sandwiched by the glass, which is then passed through a series of rollers or vacuum bagging systems to expel any air pockets. Then the assembly is heated for the initial melt. These assemblies are then heated under pressure in an autoclave (oven) to achieve the final bonded product (fully crosslinked in the case of the thermoset EVA). The tint at the top of some car windshields is in the PVB. Also, colored PC films can be combined with the thermoset EVA material, during the laminating process, in order to obtain a colored glass. Digital printing is now available for architectural applications by either printing directly to the glass and then laminating or printing directly to the PVB as is the case with the trademarked Dupont SentryGlas Expressions process. Full CMYK images can be printed to the interlayer prior to the autoclave process, and present vivid translucent representations. This process has become popular in architectural, Interior design, and signage industries. [citation needed]

Once a thermoset EVA is properly laminated during the process, the glass can be exposed frameless. There should be no water/moisture infiltration, very little discoloration, and no delamination, in the laminated glass due to the high level of bonding (crosslinking).

Newer developments have increased the thermoplastic family for the lamination of glass. Beside PVB, other important thermoplastic glass lamination materials today are Ethylene Vinyl Acetate (EVA), thermoset EVA and Thermoplastic polyurethane (TPU). The adhesion of TPU is not only high to glass, but also to polymeric interlayers. Since 2004, metallized and electroconductive polyethylene terephthalate (PET) interlayers are used as substrate for light emitting diodes and laminated to or between glass. Colored interlayers can be added to provide a permanent transparent color 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.

Top layer: Glass

Interlayer: Transparent thermoplastic materials (TPU or PVB, EVA) or transparent thermoset material (EVA)

Interlayer: LED (light emitting diodes) on transparent conductive Polymer

Interlayer: Transparent thermoplastic materials (TPU or PVB, EVA) or transparent thermoset material (EVA)

Bottom layer: Glass

Laminated glass is also sometimes used in glass sculptures and is widely utilized in architectural applications. In addition, laminated glass has applications to making bulletproof glass, penetration-proof glass, stairs, rooftops, floors, canopies, and beams.

Article body - Performance
For laminated glass, the post-breakage strength and safety are most important when analyzing its performance. Because of its brittle nature, laminated glass has structural applications, in which the interaction between the glass and its interlayer determines the failure of the panels. In testing the performance of laminated glass, the panel is subjected to impact loading and bending, where the interlayer material transfer shear stress to the glass. The stiffness in the interlayer will determine the thickness in the overall bending stiffness of the laminated glass panel. Laminated glass fails due to the cohesive failure of the interlayer and/or the connectivity between the panel and interlayer. The failure of the interlayer can occur when the interlayer material is ductile (at room temperature), or brittle and stiff (when working below glass transition temperature).

When an accident occurs, the fractured laminated glass should retain in one piece for user safety. Before breaking, the panel will be subjected to out-of-plane bending where the interlayer experiences shear stress. The laminated glass panel's stiffness and structural integrity should stay together as the fragments interlock. In any incident or accident, the laminated glass should dampen the energy of impact since the interlayer will hold the broken pieces together during impact.

Article body - Benefits
The main benefits of laminated glass (LG) includes: increased safety/security, reduced emissions, reduced noise pollution, and protection during natural disasters. Laminated glass increases safety for people during vehicle accidents since their windshield will stay together, preventing glass fragments from hurling at passengers. For security, laminated glass is difficult to break, which would prevent people from breaking in. LG can also reduce heating from the sun, allow building interiors to stay cool and reducing energy consumption. Depending on its thickness, laminated glass can disrupt sound waves when used as windows, thus reducing the noise pollution coming from the exterior. In the event of natural disasters such as hurricanes or earthquakes, laminated glass will remain intact and reduce potential injuries and deaths if windows or windshields were to break on people.

Cutting
Plastic interlayers in laminated glass make its cutting difficult. There is an unsafe practice of cutting both sides separately, pouring a flammable liquid such as denatured alcohol into the crack, and igniting it to melt the interlayer to separate the pieces.[citation needed] The following safer methods were recommended by the UK Government's Health and Safety Executive in 2005:[31]


 * Special purpose laminated cutting tables
 * Vertically-inclined saw frames
 * A blowlamp or hot air blower.
 * High pressure abrasive waterjet.

Cutting laminated glass requires a different scoring procedure since the glass has resistance to fracture. LG can be broken through breaks, which depends on the distance between the edge of the glass and its score. The most common breaks for laminated glass are pressure break, tweak break, table break, tap break, and pliers break. Pressure breaks, intended for scores that are more than 12 inches from the edge, flips the glass over on a table surface with the score facing downwards. Pressure would be applied on either sides of the score until the glass panel breaks. Tweak break, meant for scores between 4 to 6 inches from the edge, involves using one's fingertips to propagate the break along the score line. Table break, recommended for glasses with at least 12 to 18 inches from the edge, uses the table edge to break the score. For scores close to the edge, tap break is recommended at the expense of a scalloping effect on the glass edge. For this type of break, drop jaw pliers or glass pliers are used to break the glass along the score. For scores less than 1/2 to 1 inches from the edge, pliers break would use pliers to place a downwards pressure on the glass, breaking the score through an angle.

After cutting the laminated glass panels, there are different ways to separate the interlayer. The most common methods are melting it and cutting it. Before, glaziers often used denatured alcohol to melt the polyvinyl butyral (PVB) layer, however, this method proved to be dangerous as alcohol is flammable. A safer alternative is to melt the PVB lamination layer with a heat gun. Once the interlayer is melted, the separation is cut using a single-edged razor blade or a tape measure blade. With the blade, one would stroke the score and cut the PVB until the glass is separated from the interlayer completely.

Article body - Disposal
Waste disposal of laminated glass is no longer permitted in landfill in most European countries as the End of Life Vehicles Directive (ELV) is implemented. While the interlayer material cannot be easily recycled, research has been done to recycle the interlayer by mechanical processes and use them in other applications. A study by University of Surrey and Pilkington Glass proposes that waste laminated glass be placed into a separating device such as a rolling mill where the glass is fragmented and the larger cullet is mechanically detached from the inner film. The application of heat then melts the laminating plastic, usually polyvinyl butyral (PVB), enabling both the glass and the interior film to be recycled. The PVB recycling process is a simple procedure of melting and reshaping it.[22] However, the recycled PVB will have structure variations and lower strength properties than the original polymer. Also TPU is easy to recycle as all non crosslinked plastics.