Laminated Glass          Back to Glass Textbook
Laminated glass is traditionally defined as:

  1. Two or more lites of glass and one or more interlayers of plasticized polyvinyl butyral (PVB) permanently bonded together under heat and pressure;

  2. Two or more lites of glass and polycarbonate with an aliphatic urethane interlayer between glass and polycarbonate permanently bonded together under heat and pressure.

  3. Two or more lites of glass bonded with one or more interlayers of a liquid resin cured and permanently bonded together by exposure to ultraviolet light, heat, or chemicals.

  4. Two or more lites of glass with an ionoplast rigid sheet interlayer (similar to a PVB yet more rigid) permanently bonded together under heat and pressure.

  5. Two or more lites (or sheets) of polycarbonate (or acrylic) with an aliphatic urethane interlayer between polycarbonate or acrylic bonded together under heat and pressure.

  6. Two or more lites and polyester (PET) film with a polyvinyl butyral (PVB) interlayer between glass and PET permanently bonded together under heat and pressure.

Annealed, heat-treated, chemically strengthened, wired, tinted, patterned and coated glass, as well as one- and two-way mirrors, can be incorporated into the laminated unit.

This union of materials provides a variety of performance benefits in architectural, security and other specialty applications. Its most important characteristic is the ability of the interlayer to support and hold the glass when broken and/or plastic sheet when cracked. This provides for increased protection against fall-out and penetration of the opening. Most building codes require the use of laminated glass for overhead glazing as monolithic lites, or as the lower lite in multiple glazed units. Other applications include safety, security, detention, seismic-resistant, blast-resistant, bullet-resistant, burglary-resistant, hurricane/cyclic wind-resistant and sound reduction applications. Laminated glazing materials are also used in specialty applications such as aquariums, animal enclosures, glass stairs, floors and sports stadiums.

Laminated glass with PVB interlayers are generally 75% to 100% as strong as annealed glass of the same thickness depending on exposed temperatures, aspect ratio, plate size, stiffness and load duration. Laminated glass, however, can be made with heat-strengthened, fully tempered or chemically strengthened glass for additional benefits, such as increased wind-load resistance, impact resistance, or resistance to thermal stress. The ability of the interlayer to resist various kinds of penetration may also be dependent upon thickness, temperature and other variables. Check with the fabricator for any additional limitations, such as roll distortion, that may result from this additional processing of laminated glass. There are several grades of PVB having different physical properties. Care should be taken to specify the correct grade for a given application. Consult the interlayer manufacturer / glass fabricator for full details. Typical applications for laminated glass with PVB interlayers and cured resins include locations where safety glazing is required, such as doors and skylights, shower and bath doors and enclosures. Other locations where safety glazing may be specified include operable windows and fixed glazed panels, balconies, railing systems, elevators, sports stadiums, atriums, greenhouses, skylights and sloped glazing. Laminated glass resists glass fall-out from windblown debris in hurricane / cyclic-windstorm prone areas and provides various levels of security protection in seismic, blast-resistant, bullet-resistant and burglary-resistant applications.

Laminated glass with ionoplast interlayers are similar to PVB laminates; however, the rigid interlayer provides additional performance in high design pressure and high security applications where lower deflections and higher penetration resistance is required after the glass lites have been broken.

Glass-clad polycarbonate contains glass layers to the exterior and one or more polycarbonate layers on the inside. This product combines the heat, chemical and abrasion resistance of glass with the impact resistance of polycarbonate. This laminated construction may also be unbalanced or asymmetrical, where a polycarbonate layer is exposed to the interior. Although not truly a “glass-clad” product, the industry recognizes the product under the same category. Glass-clad polycarbonates provide resistance to forced entry and ballistics and are commonly used in prisons, detention centers, jails, psychiatric facilities and other architectural settings where security is a primary concern.

Organic coated glass-butyral consist of at least one lite of glass with its interior or protected surface laminated under heat and pressure to a composite sheet of PVB with a scratch-resistant polyester (PET) film. Optionally, the organic coated glass-butyral can be applied onto multiple-ply laminated glass. The composite organic coating consists of an abrasion resistant polyester-film combined with a sheet of PVB for factory lamination to glass. The PVB is used to adhere the PET film to the glass surface. The composite must face towards the building’s interior. These laminates are generally used in security applications where there is a requirement for zero spalling on the inside of a building or room following attack from the outside.

Polyester (PET) films can also be laminated inside the laminated glass using polyvinyl butyral (PVB) to bond the PET to the glass. This PET film can provide additional resistance to penetration and cyclic wind pressure.

Quality standards for laminated glass are defined in ASTM C 1172 Standard Specification for Laminated Architectural Glass and ASTM C 1349 Standard Specification for Architectural Flat Glass Clad Polycarbonate. Laminated glass for use as safety glazing is covered by ANSI Z97.1 and CPSC 16 CFR 1201 Cat. I and II.

Note: The GANA Glazing Manual and Laminated Glazing Reference Manual should be consulted for additional detailed information on laminated glass, burglar-resistant, bullet-resistant, and physical-attack resistant laminated constructions prior to specifying and using laminated glass constructions.

The above information is from the GANA Glazing Manual, 2004 Edition - the most frequently referenced resource in the architectural glass and glazing industry. The Glazing Manual is an excellent addition to any technical library. Go here to order a copy of the manual or CD-ROM. For further information on this and other GANA reference documents visit the PUBLICATIONS section of the GANA website.

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Last modified: 11/09/08