Polyvinyl butyral
Encyclopedia
Polyvinyl butyral is a resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

 usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness
Toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing; Material toughness is defined as the amount of energy per volume that a material can absorb before rupturing...

 and flexibility. It is prepared from polyvinyl alcohol
Polyvinyl alcohol
Polyvinyl alcohol is a water-soluble synthetic polymer .-Properties:...

 by reaction with butyraldehyde. The major application is laminated safety glass
Laminated glass
Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral , between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high...

 for automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 windshield
Windshield
The windshield or windscreen of an aircraft, car, bus, motorbike or tram is the front window. Modern windshields are generally made of laminated safety glass, a type of treated glass, which consists of two curved sheets of glass with a plastic layer laminated between them for safety, and are glued...

s. Tradenames for PVB-films include GlasNovations, Butacite, Saflex, S-Lec, and Trosifol.

Automotive and architectural

Laminated glass
Laminated glass
Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral , between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high...

, commonly used in the automotive and architectural fields, comprises a protective interlayer, usually polyvinyl butyral, bonded between two panels of glass. The bonding process takes place under heat and pressure. When laminated under these conditions, the PVB interlayer becomes optically clear and binds the two panes of glass together. Once sealed together, the glass "sandwich" (i.e., laminate) behaves as a single unit and looks like normal glass. The polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

 interlayer of PVB is tough and ductile, so brittle cracks will not pass from one side of the laminate to the other.

Colors

PVB interlayer can be purchased in colored sheets, such as for the blue or green "shade band" at the top edge of many automobile windshields. PVB interlayers can also be purchased in different colors for architectural laminated glass manufacture.

Solar modules

PVB has gained acceptance among manufacturers of photovoltaic thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....

 solar modules. The photovoltaic circuit is formed on a sheet of glass using thin film deposition and patterning techniques. PVB and a second sheet of glass (called back glass) are then placed directly on the circuit. The lamination of this sandwich encapsulates the circuit, protecting it from the environment. Current is extracted from the module at a sealed terminal box that is attached to the circult through a hole in the back glass. Another common laminant used in the solar industry is ethylene-vinyl acetate
Ethylene-vinyl acetate
Ethylene vinyl acetate is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene....

 (EVA).

Non-film applications

PVB resins (provided by the manufacturer in powdered or granulated form) are also utilized in a range of applications including technical ceramic (temporary) binders, inks, dye transfer ribbon inks, paints & coatings (including wash primers), binders for reflective sheet and binders for magnetic media. PVB resin is particularly useful at bonding to metals, ceramics and other inorganics.

Properties

Annealed glass, heat-strengthened or tempered glass can be used to produce laminated glass. While laminated glass will crack if struck with sufficient force, the resulting glass fragments tend to adhere to the interlayer rather than falling free and potentially causing injury.

In practice, the interlayer provides three beneficial properties to laminated glass panes: first, the interlayer functions to distribute impact forces across a greater area of the glass panes, thus increasing the impact resistance of the glass; second, the interlayer functions to bind the resulting shards if the glass is ultimately broken; third the viscoelastic interlayer undergoes plastic deformation during impact and under static loads after impact, absorbing energy and reducing penetration by the impacting object as well as reducing the energy of the impact that is transmitted to impacting object, e.g. a passenger in a car crash. Thus, the benefits of laminated glass include safety and security.

Production

PVB is a 70-year-old product. It has been the dominant interlayer material since the late 1930s. It is currently manufactured and marketed by a number of companies worldwide, including [DuPont]] (Wilmington, Delaware
Wilmington, Delaware
Wilmington is the largest city in the state of Delaware, United States, and is located at the confluence of the Christina River and Brandywine Creek, near where the Christina flows into the Delaware River. It is the county seat of New Castle County and one of the major cities in the Delaware Valley...

, USA) ("Butacite"-brand PVB), Solutia (St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...

, USA) (Saflex-brand PVB), Kuraray Europe GmbH (Frankfurt
Frankfurt
Frankfurt am Main , commonly known simply as Frankfurt, is the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2010 population of 688,249. The urban area had an estimated population of 2,300,000 in 2010...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

) ("Trosifol"-brand PVB), and Sekisui (Kyoto
Kyoto
is a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area.-History:...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

) ("S-Lec" brand PVB film and powdered PVB resins).

The market for laminated glass products is a mature one, and relatively stagnant. With only minor modifications, the PVB interlayer sold today is essentially identical to the PVB sold 30 years ago. Since its introduction in 1938, the worldwide market for PVB interlayer has been dominated by a handful of large chemical concerns. As a result, inventive efforts have tended toward methods of making the interlayer itself cheaper to manufacture, or making the interlayer easier to handle and less prone to material defects during the process of fabricating laminated glass panel.

Other interlayer materials

There are other types of interlayer materials in use, including polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

s such as Duraflex-brand thermoplastic polyurethane film, manufactured by Bayer MaterialScience
Bayer MaterialScience
Bayer MaterialScience is an independent subgroup within Bayer AG. It was created as part of the restructuring of Bayer AG from the former business group Bayer Polymers, with certain of its activities being spun off to Lanxess AG...

, Leverkusen
Leverkusen
Leverkusen is a city in North Rhine-Westphalia, Germany on the eastern bank of the Rhine. To the South, Leverkusen borders the city of Cologne and to the North is the state capital Düsseldorf....

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

. As used herein, the term "interlayer" refers to any material now known or developed in the future for manufacturing laminated glass. PVB and thermoplastic polyurethanes (TPUs) are explicitly included within the definition of "interlayer."
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