A polyurethane is any polymer consisting of a chain of organic units joined by urethane links. It is widely used in flexible and rigid foams, durable elastomers and high performance adhesives and sealants, fibers, seals, gaskets, condoms, carpet underlay, and hard plastic parts. Polyurethane products are often called "urethanes". They should not be confused with the specific substance urethane, also known as ethyl carbamate. Polyurethanes are not produced from ethyl carbamate, nor do they contain it. Polymer is a term used to describe molecules consisting of structural units and a large number of repeating units connected by covalent chemical bonds. ... Organic chemistry is a specific discipline within the subject of chemistry. ... Carbamates are a group of organic compounds sharing a common functional group with the general structure -NH(CO)O-. More precisely the carbamate group is considered an amide group with an alkoxy or hydroxy functional group next to the carbonyl group. ... Foam The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. ... The term elastomer is often used interchangeably with the term rubber, and is preferred when referring to vulcanisates. ... An adhesive is a compound that adheres or bonds two items together. ... Synthetic fibers are the result of an extensive search by scientists to increase and improve upon the supply of naturally occurring animal and plant fibers that have been used in making cloth. ... Seal on envelope A seal is an impression printed on, embossed upon, or affixed to a document (or any other object) in order to authenticate it, in lieu of or in addition to a signature. ... This article is about mechanical seals. ... A 67 m long condom on the Obelisk of Buenos Aires, Argentina, part of an awareness campaign for the 2005 World AIDS Day A condom is a device, usually made of latex, or more recently polyurethane, that is used during sexual intercourse. ... A carpet is any loom-woven, felted textile or grass floor covering. ... Urethane (also called ethyl carbamate) 1. ... Ethyl carbamate (also called urethane) is a substance first prepared in the nineteenth century. ... Ethyl carbamate (also called urethane) is a substance first prepared in the nineteenth century. ...

Production

The main polyurethane producing reaction is between a diisocyanate (aromatic and aliphatic types are available) and a polyol, typically a polyethylene glycol or polyester polyol, in the presence of catalysts and materials for controlling the cell structure, (surfactants) in the case of foams. Polyurethane can be made in a variety of densities and hardnesses by varying the type of monomer(s) used and adding other substances to modify their characteristics, notably density, or enhance their performance. Other additives can be used to improve the fire performance, stability in difficult chemical environments and other properties of the polyurethane products. Isocyanate is the chemical group of atoms -N=C=O (1 nitrogen, 1 carbon, 1 oxygen), as opposed to cyanate, -O-C≡N, which is formed from cyanogen in the normal -ate manner. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... The name polyols refers to chemical compounds containing multiple hydroxyl groups. ... Chemical structure of the polymeric polyethylene glycol Polyethylene glycol (PEG) and polyethylene oxide (PEO) are polymers having an identical structure except for chain length and end groups, and are the most commercially important polyethers. ... In chemistry, a catalyst (Greek: καταλύτης, catalytÄ“s) is a substance that decreases the activation energy of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction. ... This article concerns the structure of covert cells. ... Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ...

Though the properties of the polyurethane are determined mainly by the choice of polyol, the diisocyanate exerts some influence. The cure rate is influenced by the functional group reactivity and the number of functional isocyanate groups. The mechanical properties are influenced by the functionality and the molecular shape. The choice of diisocyanate also affects the stability of the polyurethane upon exposure to light. Polyurethanes made with aromatic diisocyanates yellow with exposure to light, whereas those made with aliphatic diisocyanates are stable.^[1]

Softer, elastic, and more flexible polyurethanes result when linear difunctional polyethylene glycol segments, commonly called polyether polyols, are used to create the urethane links. This strategy is used to make spandex elastomeric fibers and soft rubber parts, as well as foam rubber. More rigid products result if polyfunctional polyols are used, as these create a three-dimensional cross-linked structure which, again, can be in the form of a low-density foam. In solid mechanics, elasticity is the property of materials which undergo reversible deformations under applied loads. ... Urethane (also called ethyl carbamate) 1. ... Example of spandex Spandex or elastane is a synthetic fiber known for its exceptional elasticity (stretchability). ...

An even more rigid foam can be made with the use of specialty trimerization catalysts which create cyclic structures within the foam matrix, giving a harder, more thermally stable structure, designated as polyisocyanurate foams. Such properties are desired in rigid foam products used in the construction sector.

Polyurethane foam (including foam rubber) is usually made by adding small amounts of volatile materials, so-called blowing agents, to the reaction mixture. These can be simple volatile chemicals such as acetone or methylene chloride, or more sophisticated fluorocarbons which yield important performance characteristics, primarily thermal insulation.

Another common route to produce foams is the addition of water to one of the liquid precursors of polyurethane before they are mixed together. This reacts with a portion of the isocyanate, generating carbon dioxide throughout the liquid, creating relatively uniform bubbles which then harden to form a solid foam as polymerization progresses.

The presence of water means that a small proportion of reactions result in urea linkages —NC(=O)N—, rather than urethane linkages, so that the resulting material should technically be called poly(urethane-co-urea).

Careful control of viscoelastic properties — by modifying the catalysts and polyols used —can lead to memory foam, which is much softer at skin temperature than at room temperature.

There are then two main foam variants: one in which most of the foam bubbles (cells) remain closed, and the gas(es) remains trapped, the other being systems which have mostly open cells, resulting after a critical stage in the foam-making process (if cells did not form, or became open too soon, foam would not be created). This is a vitally important process: if the flexible foams have closed cells, their softness is severely compromised, they become pneumatic in feel, rather than soft; so, generally speaking, flexible foams are required to be open-celled.

The opposite is the case with most rigid foams. Here, retention of the cell gas is desired since this gas (especially the fluorocarbons referred to above) gives the foams their key characteristic: high thermal insulation performance.

A third foam variant, called microcellular foam, yields the tough elastomeric materials typically experienced in the coverings of car steering wheels and other interior automotive components.

Uses

Polyurethane products have many uses. Over three quarters of the global consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. In both cases, the foam is usually behind other materials: flexible foams are behind upholstery fabrics in commercial and domestic furniture; rigid foams are inside the metal and plastic walls of most refrigerators and freezers, or behind paper, metals and other surface materials in the case of thermal insulation panels in the construction sector. It has been suggested that this article or section be merged into refrigeration. ... Insulation must not be confused with insolation (the latter word has an o where the former has a u). Insulation is any material used to reduce or “slow down” or “resist” the flow of energy. ...

The precursors of expanding polyurethane foam are available in many forms, for use in insulation, sound deadening, flotation, packing material, and even cast-in-place upholstery padding. Since they adhere to most surfaces and automatically fill voids, they have become quite popular in these applications.

Varnish

Polyurethane materials are used in coatings and varnishes used in furniture manufacture, carpentry or woodworking. A polyurethane varnish is frequently employed as a finishing coat to protect or seal wood. This use results in a hard, inflexible coat that is popular for protecting floors, but considered by some to be unsuitable for finishing furniture or other detailed pieces. Polyurethane varnish tends to de-laminate if subjected to heat or shock, leaving transparent or white patches. Because it doesn't penetrate into the wood, polyurethane also lacks the lustre of other treatments. Varnish is a finish applied to wood or other surfaces in order to provide a clear, hard, durable, protective finish. ... A Shaker chair. ... A carpenter is a skilled craftsman who performs carpentry -- a wide range of woodworking that includes constructing buildings, furniture, and other large objects out of wood. ... Artists can use woodworking to create delicate sculptures. ... Wood finishing refers to the process of embellishing and/or protecting the surface of wooden objects. ...

Computer mousepads

Polyurethane is used on the bottom of some mousepads.and power transmission belts

Glue

Polyurethane is used as an adhesive, especially as a woodworking glue. Its main advantage over more traditional wood glues is its water resistance. It was introduced in the general North American market in the 1990s as Gorilla Glue and Excel, but has been used much longer in Europe. An adhesive is a compound that adheres or bonds two items together. ... Wood glues are adhesives used to tightly bond pieces of wood together. ...

Wheels

Polyurethane is also used in making solid tires. Modern roller blading and skateboarding became economical only with the introduction of tough, abrasion-resistant polyurethane parts. Other constructions have been developed for pneumatic tires, and microcellular foam variants are widely used in tires on wheelchairs, bicycles and other such uses. These latter foam types are also widely encountered in car steering wheels and other interior and exterior automotive parts, including bumpers and fenders. Tires may refer to: the plural of tire the Italian name for Tiers, Italy, a town in South Tyrol, Italy Category: ... Roller skating girl in Rome, Italy (soul grind) Roller skating is travelling on smooth terrain with roller skates. ... This article or section does not cite its references or sources. ...

Furniture

Polyurethane is also used in furniture manufacture for casting soft edges around table tops and panel that are stylish, very durable and prevent injury. These are used in school tables, hospital and bank furniture as well as shop counters and displays.

Automobile seats

Flexible and semi-flexible polyurethane foams are used extensively for interior components of automobiles, in seats, headrests, armrests, roof liners and instrument panels. This article or section does not cite its references or sources. ...

Polyurethanes are used to make automobile seats in a remarkable manner. The seat manufacturer has a mold for each seat model. The mold is a closeable "clamshell" sort of structure that will allow quick casting of the seat cushion, so-called molded flexible foam, which is then upholstered after removal from the mold.

It is possible to combine these two steps, so-called in-situ, foam-in-fabric or direct moulding. In this case, the inner surfaces of the mold have hundreds of small holes that all connect to a vacuum manifold. This creates a constant air flow from the core of the mold to the manifold. The assembly operator first places a complete, fully-assembled seat cover in the mold and adjusts it so that the vacuum in the manifold pulls the seat cover snugly against the mold surface. In some operations, this effect is improved by adding a thin pliable plastic film as a backing to the fabric to help the vacuum work more effectively. When the seat cover is in place, the operator then places the metal frame of the seat into the mold and closes the mold. At this point the mold contains what could be visualized as a "hollow seat", a seat fabric held in the correct position by the vacuum manifold and containing a hollow space with the metal frame in place.

The next step is to inject the polyurethane chemical mixture into the mold cavity. This is a two-part mixture that is metered exactly through a mixing head. Then the mold is held at a preset reaction temperature until the chemical mixture has foamed, filled the mold, and formed a stable soft foam. The time required is about two to three minutes, depending on the size of the seat and the precise formulation and operating conditions. Then the mold is usually opened slightly for a minute or two for an additional cure time, before the fully upholstered seat is removed. The operator then trims any excess seat cover fabric and puts the finished seat onto a conveyor.

Houses, sculptures, and decorations

The walls and ceiling (not just the insulation) of the futuristic Xanadu House were built out of polyurethane foam. Domed ceilings and other odd shapes are easier to make with foam than with wood. Foam was used to build oddly-shaped buildings, statues, and decorations in the Seuss Landing section of the Islands of Adventure theme park. The exterior of the Xanadu House in Kissimmee, Florida in 1994 The Xanadu Houses were a series of experimental homes, built to showcase computers and automation in the home. ... The Incredible Hulk Coaster at Islands of Adventure Islands of Adventure is a theme park located in Orlando, Florida. ...

Watercraft

Some surfboards are made with a solid polyurethane core.

The hull of the Boston Whaler motor boat is polyurethane foam sandwiched in a fiberglass skin. The foam provides strength, buoyancy, and sound deadening. Boston Whaler outward bound in Boston Harbor, 2002. ...

Condoms

Several types of condoms are made out of polyurethane, including the Trojan Supra and Durex Avanti. These condoms are ideal for users sensitive or allergic to traditional latex condoms, and have been tested to provide the same level of protection from STDs and pregnancy. A 67 m long condom on the Obelisk of Buenos Aires, Argentina, part of an awareness campaign for the 2005 World AIDS Day A condom is a device, usually made of latex, or more recently polyurethane, that is used during sexual intercourse. ... A Trojan condom The Church & Dwight Co. ... The brand Durex is used for a number of unrelated products around the world. ... This article needs cleanup. ... The LaTeX logo, typeset with LaTeX , written as LaTeX in plain text, is a document preparation system for the (TeX) typesetting program. ... Sexually transmitted diseases (STDs) — also known as sexually transmissible diseases, sexually transmitted infections (STIs) or (infrequently) venereal diseases (VD) or social disease — are diseases or infections that have a significant probability of transmission between humans by means of sexual contact, vaginal intercourse, oral sex, and/or anal sex. ... Pregnant woman at 26-week gestation A pregnant woman near the end of her term Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. ...

Construction sealants and firestopping

Head-of-Wall Firestop Joint: the presence of penetrants demonstrates the need to have both operational and fire-tested compatibility between the joint sealant and mechanical/electrical through-penetrations. In other words, it is easier to insist on the use of joint firestops that can also be used for penetration seals, as otherwise penetrants may be run by mechanical and electrical subtrades that unintentionally void the fire-resistance rating of the wall, which jeopardises the entire fire safety plan in place for a building.

Head-of-Wall Firestop Joint penetrated by both electrical and mechanical services, demonstrating the need for operational and fire-tested compatibility between the joint firestop system and penetrants, be they electrical, mechanical or structural.

PU sealants are available in 1, 2 and even 3 part systems, either in cartridge, bucket or drum format. The major (though not exclusive) supplier of construction urethanes in the U.S. is Tremco, of Cleveland, Ohio. A version of their PU sealant is also sold for firestopping applications. Obviously, the sealant by itself provides no serious hindrance to fire, as its hydrocarbon bonds readily support combustion. However, when backed by inorganic insulation, such as rockwool or ceramic fibres, it can act as an effective seal to thwart smoke and hose-stream passage, particularly in inorganic joints. It is, however, advisable to avoid direct contact with metallic penetrants and through-penetrating cables, as the heat carried by the penetrants may jeopardise the sealant. This, however, requires a lot of vigilance. In concrete to concrete, or concrete to masonry joints, however, that are free of mechanical or electrical penetrants, it works well and dependably. As with all passive fire protection products and systems, the key to code compliance is demonstrable bounding. A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... A penetrant is the cause for a service penetration firestop. ... A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... Wikipedia does not yet have an article with this exact name. ... Official language(s) None Capital Columbus Largest city Columbus Largest metro area Cleveland Area  Ranked 34th  - Total 44,825 sq mi (116,096 km²)  - Width 220 miles (355 km)  - Length 220 miles (355 km)  - % water 8. ... A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... A large bonfire. ... Hydrocarbons are refined at oil refineries and processed at chemical plants In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon (C) and hydrogen (H). ... Insulation may mean: Electrical insulation Thermal insulation Soundproofing, also known as acoustic insulation. ... A penetrant is the cause for a service penetration firestop. ... In physics, heat, symbolized by Q, is defined as energy in transit. ... Pouring a concrete floor for a commercial building, (slab-on-grade) Installing rebar in a floor slab during a concrete pour In construction, concrete is a composite building material made from the combination of aggregate and a cement binder. ... Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent [1] cable coating. ... System (from the Latin (systÄ“ma), and this from the Greek (sustÄ“ma)) is an assemblage of entity/objects, real or abstract, comprising a whole with each and every component/element interacting or related to another one. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

See also

• Firestop
• Silicone
• Passive fire protection
• Bounding
• Penetrant

A firestop is a passive fire protection system of various components used to seal openings in fire-resistance rated wall and/or floor assemblies through bounding. ... Silicone caulking can be used as a basic sealant against water and air penetration. ... Fire-resistance rated wall assembly with fire door, cable tray penetration and intumescent [1] cable coating. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... A penetrant is the cause for a service penetration firestop. ...

References

1. ^ Randall, David, Lee, Steve (2002). The Polyurethanes Book. New York: Wiley. ISBN 0-470-85041-8.

External links

• Polyurethane synthesis
• Polyurethane Foam Association
• Urethanes Technology magazine
• Link page to external chemical sources.