Safety glass

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Broken safety glass shows a characteristic circular "spider web" pattern Broken glass 1040821 Nevit.jpg
Broken safety glass shows a characteristic circular "spider web" pattern

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 (also known as wired glass). Toughened glass was invented in 1874 by Francois Barthelemy Alfred Royer de la Bastie. [1] Wire mesh glass was invented in 1892 by Frank Shuman. [2] [3] Laminated glass was invented in 1903 by the French chemist Édouard Bénédictus (1878–1930). [4]

Contents

These three approaches can easily be combined, allowing for the creation of glass that is at the same time toughened, laminated, and contains a wire mesh. However, combination of a wire mesh with other techniques is unusual, as it typically betrays their individual qualities. In many developed countries[ which? ] safety glass is part of the building regulations making properties safer. [5]

Toughened glass

Broken tempered glass showing the shape of the granular chunks Broken safety glas 20060407 268.jpg
Broken tempered glass showing the shape of the granular chunks

Toughened glass is processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. [6] Tempering, by design, creates balanced internal stresses which causes the glass sheet, when broken, to crumble into small granular chunks of similar size and shape instead of splintering into random, jagged shards. The granular chunks are less likely to cause injury.

As a result of its safety and strength, tempered glass is used in a variety of demanding applications, including passenger vehicle windows, shower doors, architectural glass doors and tables, refrigerator trays, as a component of bulletproof glass, for diving masks, and various types of plates and cookware. In the United States, since 1977 Federal law has required safety glass located within doors and tub and shower enclosures. [7]

Laminated glass

Broken laminated safety glass, with the interlayer exposed at the top of the picture Laminated safety glas vandalised 20060407 340.jpg
Broken laminated safety glass, with the interlayer exposed at the top of the picture

Laminated glass is composed of layers of glass and plastic held together by an interlayer. [8] When laminated glass is broken, it is held in place by an interlayer, typically of polyvinyl butyral (PVB), between its two or more layers of glass, which crumble into small pieces. The interlayer keeps the layers of glass bonded even when broken, and its toughening prevents the glass from breaking up into large sharp pieces. [9] This produces a characteristic "spider web" cracking pattern (radial and concentric cracks) when the impact is not enough to completely pierce the glass. [10]

Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered. 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. The PVB interlayer also gives the glass a much higher sound insulation rating, due to the damping effect, and also blocks most of the incoming UV radiation (88% in window glass and 97.4% in windscreen glass). [11]

Wire mesh glass

Wire-mesh-reinforced glass in the Lloyd's Building Cmglee Lloyds building wire glass.jpg
Wire-mesh-reinforced glass in the Lloyd's Building

Wire mesh glass (also known as Georgian Wired Glass) has a grid or mesh of thin metal wire embedded within the glass. Wired glass is used in the US for its fire-resistant abilities, and is well-rated to withstand both heat and hose streams. This is why wired glass exclusively is used on service elevators to prevent fire ingress to the shaft, and also why it is commonly found in institutional settings which are often well-protected and partitioned against fire. [12] [ failed verification ] The wire prevents the glass from falling out of the frame even if it cracks under thermal stress, and is far more heat-resistant than a laminating material.

Wired glass, as it is typically described, does not perform the function most individuals associate with it. The presence of the wire mesh appears to be a strengthening component, as it is metallic, and conjures up the idea of rebar in reinforced concrete or other such examples. Despite this belief, wired glass is actually weaker than unwired glass due to the incursions of the wire into the structure of the glass. Wired glass often may cause heightened injury in comparison to unwired glass, as the wire amplifies the irregularity of any fractures. This has led to a decline in its use institutionally, particularly in schools. [13]

In recent years, new materials have become available that offer both fire-ratings and safety ratings so the continued use of wired glass is being debated worldwide. The US International Building Code effectively banned wired glass in 2006. [14]

Canada's building codes still permit the use of wired glass but the codes are being reviewed and traditional wired glass is expected to be greatly restricted in its use. [15] Australia has no similar review taking place. [16]

See also

Related Research Articles

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The windshield or windscreen of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. Modern windshields are generally made of laminated safety glass, a type of treated glass, which consists of, typically, two curved sheets of glass with a plastic layer laminated between them for safety, and bonded into the window frame.

<span class="mw-page-title-main">Solutia</span> American manufacturer of materials and specialty chemicals

Solutia Inc. was an American manufacturer of materials and specialty chemicals including polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), and thermoplastic polyurethane (TPU) interlayers for laminated glass, aftermarket window films, protective barrier and conductive films, and rubber processing chemicals. The company was formed on September 1, 1997, as a divestiture of the Monsanto Company chemical business. In July 2012, the company was acquired by Eastman Chemical Company.

<span class="mw-page-title-main">Curtain wall (architecture)</span> Outer non-structural walls of a building

A curtain wall is an exterior covering of a building in which the outer walls are non-structural, instead serving to protect the interior of the building from the elements. Because the curtain wall façade carries no structural load beyond its own dead load weight, it can be made of lightweight materials. The wall transfers lateral wind loads upon it to the main building structure through connections at floors or columns of the building.

<span class="mw-page-title-main">Polyvinyl butyral</span> Chemical compound

Polyvinyl butyral 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 major application is laminated safety glass for automobile windshields. Trade names for PVB-films include KB PVB, GUTMANN PVB, Saflex, GlasNovations, Butacite, WINLITE, S-Lec, Trosifol and EVERLAM. PVB is also available as 3D printer filament that is stronger and more heat resistant than polylactic acid (PLA).

<span class="mw-page-title-main">Brittleness</span> Liability of breakage from stress without significant plastic deformation

A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a sharp snapping sound.

<span class="mw-page-title-main">Glazier</span> Profession

A glazier is a tradesperson responsible for cutting, installing, and removing glass. They also refer to blueprints to figure out the size, shape, and location of the glass in the building. They may have to consider the type and size of scaffolding they need to stand on to fit and install the glass. Glaziers may work with glass in various surfaces and settings, such as cutting and installing windows, doors, shower doors, skylights, storefronts, display cases, mirrors, facades, interior walls, ceilings, and tabletops.

<span class="mw-page-title-main">Fire door</span> Fire resistant door

A fire door is a door with a fire-resistance rating used as part of a passive fire protection system to reduce the spread of fire and smoke between separate compartments of a structure and to enable safe egress from a building or structure or ship. In North American building codes, it, along with fire dampers, is often referred to as a closure, which can be derated compared against the fire separation that contains it, provided that this barrier is not a firewall or an occupancy separation. In Europe national standards for fire doors have been harmonised with the introduction of the new standard EN 16034, which refers to fire doors as fire-resisting door sets. Starting September 2016, a common CE marking procedure was available abolishing trade barriers within the European Union for these types of products. In the UK, it is Part B of the Building Regulations that sets out the minimum requirements for the fire protection that must be implemented in all dwellings this includes the use of fire doors. All fire doors must be installed with the appropriate fire resistant fittings, such as the frame and door hardware, for it to fully comply with any fire regulations.

<span class="mw-page-title-main">Architectural glass</span>

Architectural glass is glass that is used as a building material. It is most typically used as transparent glazing material in the building envelope, including windows in the external walls. Glass is also used for internal partitions and as an architectural feature. When used in buildings, glass is often of a safety type, which include reinforced, toughened and laminated glasses.

<span class="mw-page-title-main">Tempered glass</span> Type of safety glass processed to increase its strength

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 tension. Such stresses cause the glass, when broken, to shatter into small granular chunks instead of splintering into jagged shards as ordinary annealed glass does. The granular chunks are less likely to cause injury.

<span class="mw-page-title-main">Laminated glass</span> Type of safety glass with a thin polymer interlayer that holds together when shattered

Laminated glass is a type of safety glass consisting of two or more layers of glass with one or more thin polymer interlayers between them which prevent the glass from breaking into large sharp pieces. Breaking produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass.

Safety and security window films are polyester or PET films that are applied to glass and glazing in order to hold them together if the glass is shattered. The main difference between film and laminated glass is that these shatter safe films can be applied to the glass or glazing after manufacture or installation. I.e., these films are retrofit products. These films are used widely all over the world; they can be found on trains, buses, cars, and buildings.

Chemically strengthened glass is a type of glass that has increased strength as a result of a post-production chemical process. When broken, it still shatters in long pointed splinters similar to float glass. For this reason, it is not considered a safety glass and must be laminated if a safety glass is required. However, chemically strengthened glass is typically six to eight times the strength of float glass. The most common trademark for this kind of glass is Gorilla glass.

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Vehicle glass is glass used to provide light access to motor vehicles. It includes windscreens, side and rear windows, and glass panel roofs.

Triplex Safety Glass was a British brand of toughened glass and laminated glass. The marque is often seen on vehicle and aircraft windscreens.

<span class="mw-page-title-main">Glazing (window)</span> Part of a wall or window, made of glass

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<span class="mw-page-title-main">Frank Shuman</span> American inventor, engineer and solar energy pioneer (1862-1918)

Frank Shuman was an American inventor, engineer and solar energy pioneer known for his work on solar engines, especially those that used solar energy to heat water that would produce steam.

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<span class="mw-page-title-main">Glass breaker</span> Safety device

A glass breaker is a hand tool designed to break through a window glass in an emergency. It is a common safety device found in vehicles to aid in the emergency extrication of occupants from a vehicle, as well as in some buildings.

Composite glass is the collective term for a laminate having at least two glass panes which are in each case connected by means of an adhesive intermediate layer composed of plastic, e.g. by means of a casting resin or a thermoplastic composite film, which is highly tear-resistant and is viscoelastic. Composite glass should not be confused with composite windows.

References

  1. "Glass." The Encyclopædia Britannica : A Dictionary of Arts, Sciences and General Literature. 9th ed. (American reprint). Vol. 10. Philadelphia: Sherman & co., 1894. 595. Print.
  2. Frank Shuman, "Process of embedding wire-netting in glass", U.S. Patent no. 483,021 (filed: July 6, 1892; issued: September 20, 1892).
  3. "Northeast Philadelphia Hall of Fame Announces 2012 Inductees" (press release). Mayfair Civic Association, April 26, 2010.
  4. See:
  5. Hampton, Simon (15 March 2021). "Safety Glazing Glazing Glass Safety Guide For Landlord 2021" . Retrieved 2021-05-16.
  6. Schittich, Christian; Staib, Gerald; Balkow, Dieter; Schuler, Matthias; Sobek, Werner (2007-01-01). Glass Construction Manual. Walter de Gruyter. ISBN   9783034615549.
  7. "SAFETY STANDARD FOR ARCHITECTURAL GLAZING MATERIALS". www.govinfo.gov. Retrieved 2021-05-16.
  8. Wurm, Jan (2007). Glass Structures: Design and Construction of Self-supporting Skins. Springer Science & Business Media. ISBN   9783764376086.
  9. McMorrough, Julia (August 2013). The Architecture Reference & Specification Book: Everything Architects Need to Know Every Day. Rockport Publishers. ISBN   9781592538485.
  10. Metcalfe, Peter; Metcalfe, Roger (2004). Excel Senior High School: Engineering Studies. Pascal Press. ISBN   9781741250510.
  11. Wei Gao; Daniel L. Schmoldt; James R. Slusser (8 September 2010). UV Radiation in Global Climate Change: Measurements, Modeling and Effects on Ecosystems. Springer Science & Business Media. p. 195. ISBN   978-3-642-03313-1.
  12. NFPA 80: Standard for Fire Doors and Other Opening Protectives. United States: NFPA. 2010. pp. K.6. ASIN   B0046MEGF8.
  13. Fatima, Sahar (August 25, 2014). "Industry experts question the safety of wired glass used in schools". The Globe and Mail.
  14. Lane, Gordon. "Wired Safety Glass Deemed a Serious Hazard". Sourcable. Strata News. Retrieved 1 December 2014.
  15. "Unsafe Wire Glass in Canada". Unsafe Wire Glass in Canada. Glassopolis. Retrieved 26 April 2016.
  16. Lane, Gordon. "Wired Safety Glass Deemed a Serious Hazard". Sourcable. Strata News. Retrieved 1 December 2014.