Laminated glass (LG) is a type of
safety glass
Safety glass is glass with additional safety features that make it less likely to break, or less likely to pose a threat when broken. Common designs include toughened glass (also known as tempered glass), laminated glass, and wire mesh 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
Polyvinyl butyral (or PVB) is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The majo ...
(PVB),
ethylene-vinyl acetate (EVA), lonoplast polymers, cast in place (CIP) liquid resin, or
thermoplastic polyurethane
Thermoplastic polyurethane (TPU) is any of a class of polyurethane plastics with many properties, including elasticity, transparency, and resistance to oil, grease, and abrasion. Technically, they are thermoplastic elastomers consisting of linea ...
(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
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing building ...
,
glazing,
automobile safety
Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design ...
,
photovoltaic,
UV protection, and artistic expression.
The most common use of laminated glass is skylight glazing and automobile
windshield
The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. ...
s. In geographical areas requiring hurricane-resistant construction, laminated glass is often used in exterior storefronts,
curtain walls, and
window
A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...
s.
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.
History
![03262012Demonstraciones rescate erum fabian acuña134](https://upload.wikimedia.org/wikipedia/commons/c/ce/03262012Demonstraciones_rescate_erum_fabian_acu%C3%B1a134.JPG)
In 1902, the French ''Le Carbone'' corporation obtained a patent for coating glass objects with
celluloid
Celluloids are a class of materials produced by mixing nitrocellulose and camphor, often with added dyes and other agents. Once much more common for its use as photographic film before the advent of safer methods, celluloid's common contemporary ...
to render them less susceptible to cracking or breaking.
Laminated glass was invented in 1903 by the
French chemist
Édouard Bénédictus (1878–1930), inspired by a laboratory accident: a glass flask had become coated with the plastic
cellulose nitrate
Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid an ...
, and when dropped it shattered but did not break into pieces. In 1909 Bénédictus filed a patent, after hearing about a car accident where two women were severely injured by glass debris. In 1911, he formed the ''Société du Verre Triplex'', which fabricated a glass-plastic
composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
...
to reduce injuries in
car accidents. Production of Triplex glass was slow and painstaking, so it was expensive; it was not immediately widely adopted by
automobile
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarde ...
manufacturers, but laminated glass was widely used in the eyepieces of
gas masks during
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
. In 1912, the process was licensed to the English Triplex Safety Glass Company. Subsequently, in the United States, both
Libbey-Owens-Ford
The Libbey-Owens-Ford Company (LOF) was a producer of flat glass for the automotive and building products industries both for original equipment manufacturers and for replacement use. The company's headquarters and main factories were located in T ...
and
Du Pont with
Pittsburgh Plate Glass
PPG Industries, Inc. is an American Fortune 500 company and global supplier of paints, coatings, and specialty materials. With headquarters in Pittsburgh, Pennsylvania, PPG operates in more than 70 countries around the globe. By revenue it is ...
produced Triplex glass.
Meanwhile, in 1905, John Crewe Wood, a solicitor in Swindon, Wiltshire, England, patented a laminated glass for use in windshields. The layers of glass were bonded together by
Canada balsam. In 1906, he founded the Safety Motor Screen Company to produce and sell his product.
In 1927, the Canadian chemists Howard W. Matheson and Frederick W. Skirrow invented the plastic
polyvinyl butyral
Polyvinyl butyral (or PVB) is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The majo ...
(PVB). By 1936, United States companies had discovered that laminated "safety glass" consisting of a layer of polyvinyl butyral between two layers of glass would not discolor and was not easily penetrated during accidents. Within five years, the new safety glass had substantially replaced its predecessor.
In the
Road Traffic Act of 1930, the British Parliament required new cars to have safety-glass windshields. However, that regulation did not specifically require laminated glass.
By 1939, some of "Indestructo" safety glass was being used every year in vehicles produced at the
Ford Motor Company works in Dagenham, England.
"Indestructo" safety glass was manufactured by British IndestructÕ Glass, Ltd. of London.
[ This was the laminated glass used by the Ford Motor Company in 1939, chosen because "it gives the most complete protection. In addition to being splinter-proof, it is crystal clear and permanently non-discolourable."][ This quote hints at some of the technical issues, problems and concerns that stopped laminated glass from being widely used in automobiles immediately after it was invented.
]
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 with multiple laminates and thicker glass. Bullet-resistant glass, a type of laminated glass, is usually constructed using polycarbonate, thermoplastic materials, thermoset EVA, and layers of laminated glass. In automobiles, the laminated glass panel is around 6.5 mm thick, in comparison to airplane glass being three times as thick. In airliners on the front and side cockpit windows, there is often three plies of 4 mm toughened glass with 2.6 mm thick PVB between them. This is one of the makeups used for the Boeing 747 cockpit side windows. The BAC/SAF Concorde forward pressure windshields had 7 plies, 4 glass and 3 PVB total thickness 38 mm. 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.
Production
Modern laminated glass is produced by bonding two or more layers of ordinary annealed or tempered glass
Tempered or toughened glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tensi ...
together with a plastic interlayer, usually polyvinyl butyral
Polyvinyl butyral (or PVB) is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The majo ...
(PVB), Thermoplastic Polyurethane
Thermoplastic polyurethane (TPU) is any of a class of polyurethane plastics with many properties, including elasticity, transparency, and resistance to oil, grease, and abrasion. Technically, they are thermoplastic elastomers consisting of linea ...
(TPU) or ethylene-vinyl acetate (cross-linked EVA). The interlayer is meant to improve the 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
An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilizati ...
(oven) to achieve the final bonded product (fully crosslinked in the case of the thermoset EVA). The tint at the top of some car windshield
The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. ...
s is in the PVB. Also, colored PC films can be combined with the thermoset EVA material, during the laminating
Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing materia ...
process, in order to obtain a colored glass
Glass coloring and color marking may be obtained in several ways.
# by the addition of ''coloring ions'',Bernard H. W. S. De Jong, Ruud G. C. Beerkens, Peter A. van Nijnatten: "Glass", in: "Ullmann's Encyclopedia of Industrial Chemistry"; Wiley-VC ...
. Digital printing
Digital printing is a method of printing from a digital-based image directly to a variety of media. It usually refers to professional printing where small-run jobs from desktop publishing and other digital sources are printed using large-format ...
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
The CMYK color model (also known as process color, or four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation ''CMYK'' refers ...
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
Interior design is the art and science of enhancing the interior of a building to achieve a healthier and more aesthetically pleasing environment for the people using the space. An interior designer is someone who plans, researches, coordi ...
, and signage industries.
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 Cross-linking may refer to
*Cross-link
In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers ca ...
).
Newer developments have increased the thermoplastic
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains associate ...
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
Thermoplastic polyurethane (TPU) is any of a class of polyurethane plastics with many properties, including elasticity, transparency, and resistance to oil, grease, and abrasion. Technically, they are thermoplastic elastomers consisting of linea ...
(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
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
* Interlayer: Transparent thermoplastic
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains associate ...
materials (TPU or PVB, EVA) or transparent thermoset
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer ( resin). Curing is induced by heat or suitable radiation ...
material (EVA)
* Interlayer: LED (light emitting diodes
A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
) on transparent conductive Polymer
* Interlayer: Transparent thermoplastic
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains associate ...
materials (TPU or PVB, EVA) or transparent thermoset
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer ( resin). Curing is induced by heat or suitable radiation ...
material (EVA)
* Bottom layer: Glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
Laminated glass is also sometimes used in glass sculptures and is widely utilized in architectural applications. In addition, laminated glass has applications in making bulletproof glass
Bulletproof glass, ballistic glass, transparent armor, or bullet-resistant glass is a strong and optically transparent material that is particularly resistant to penetration by projectiles. Like any other material, it is not completely impenetr ...
, penetration-proof glass, stairs, rooftops, floors, canopies, and beams.
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).
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
Denatured alcohol (also called methylated spirits in Australia, Canada, Ireland, New Zealand, South Africa, and the United Kingdom; wood spirit; and denatured rectified spirit) is ethanol that has additives to make it poisonous, bad-tasting, foul ...
into the crack, and igniting it to melt the interlayer to separate the pieces. The following safer methods were recommended by the UK Government's Health and Safety Executive in 2005:
*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 and 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
Polyvinyl butyral (or PVB) is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The majo ...
(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.
Repair
According to the United States National Windshield Repair Association, laminated glass repair is possible for minor impact damage using a process that involves drilling into the fractured glass to reach the lamination layer. Special clear adhesive resin is injected under pressure and then cured with ultraviolet light. When done properly, the strength and clarity is sufficiently restored for most safety related purposes. The process is widely used to repair large industrial automotive windshields where the damage does not interfere with the view of the driver.
Disposal
Waste disposal
Waste management or waste disposal includes the processes and actions required to manage waste from its inception to its final disposal.
This includes the collection, transport, treatment and disposal of waste, together with monitorin ...
of laminated glass is no longer permitted in landfill in most European countries as the End of Life Vehicles Directive
The End of Life Vehicles Directive is a Directive of the European Union addressing the end of life for automotive products. Every year, motor vehicles which have reached the end of their useful lives create between 8 and 9 million tonnes of ...
(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
Pilkington is a Japanese-owned glass-manufacturing company which is based in Lathom, Lancashire, United Kingdom. In the UK it includes several legal entities and is a subsidiary of Japanese company NSG Group.
Prior to its acquisition by NSG ...
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
Glass recycling is the processing of waste glass into usable products. Glass that is crushed or imploded and ready to be remelted is called cullet. There are two types of cullet: internal and external. Internal cullet is composed of defective p ...
is mechanically detached from the inner film. The application of heat then melts the laminating plastic, usually polyvinyl butyral
Polyvinyl butyral (or PVB) is a resin mostly used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The majo ...
(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.Laminated Car Windscreen Recycling
Archived 2008-10-31, retrieved 2014-07-23 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.
See also
*Toughened glass
Tempered or toughened glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tens ...
*BS 857 BS 857:1967 is a currently in-use British Standard
British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. ...
* LED Film
* Composite glass
References
External links
UNECE Reg. 43
UN Regulation on automobile safety glazing materials
BS 857:1967
British specification for safety glass for land transport
{{DEFAULTSORT:Laminated Glass
Glass coating and surface modification
Vehicle technology
eo:Kirasvitro
ta:ஒட்டுக் கண்ணாடி