Laminated Glass
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Laminated glass is traditionally defined as:
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Two or more lites of glass and
one or more interlayers of plasticized polyvinyl butyral (PVB)
permanently bonded together under heat and pressure;
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Two or more lites of glass and
polycarbonate with an aliphatic urethane interlayer between glass
and polycarbonate permanently bonded together under heat and
pressure.
-
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.
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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.
-
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.
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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.
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