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What is the polyurethane foam (PU FOAM)?
(Soft polyurethane foam or semi-rigid)

(1) polyurethane
Commonly abbreviated PU is any polymer which consists of a chain of organic units joined by urethane links. Polyurethane polymers are formed by reacting a monomer containing at least two isocyanate groups with another functional monomer containing at least two alcohol groups in the presence of a catalyst. Polyurethane formulations cover a wide range of stiffness, hardness and density. These Materials include low density flexible foam used in upholstery and bedding, low density rigid foam used for thermal insulation, soft elastomers solids used for gel pads and rollers for printing, and hard solid plastics used as electronic instrument bezels and structural parts. Polyurethanes are widely used in high-strength flexible foam seating, rigid foam insulation panels, microcellular foam seals and gaskets, durable wheels elastomers and tires, electrical potting compounds, adhesives and sealants, high-performance, Spandex fibers, seals, gaskets, carpet underlay, and parts hard plastic. Polyurethane products are often called "urethanes". Not to be confused with the specific substance urethane, also known as carbamate ethyl. Polyurethanes are produced from ethyl carbamate, nor do they contain.

Upholstery is the work of providing furniture, especially seats, with padding, springs, straps, and fabric or leather. The word "upholstery" comes from the Middle English words and Holden, which means support. The term is applied to domestic furniture and also for applications in automobiles and boats. A person who works with upholstery is called an upholsterer, an apprentice upholsterer is sometimes called an outsider or trimmer.

Polyurethane products have many uses. More than three-quarters of global consumption of polyurethane products is in the form of foams, with flexible and rigid types being approximately the same size in the market. In both cases, the foam is usually behind other materials: flexible foams are behind upholstery fabrics household furniture and commercial 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. Its use in garments is growing: for example, in the lining of the cups of brassieres. Polyurethane is also used for moldings which include door frames, columns, balusters, window headers, pediments, medallions and rosettes.

The precursors of expanding polyurethane foam are available in many forms, for use in insulation, insulation, flotation, coating industrial packaging material, and even issued in the place upholstery padding. Given that adhere to most surfaces and automatically fill in the gaps have become very popular in these applications.

Chemistry
Polyurethanes are in the class of compounds called reaction polymers such as epoxies, polyesters saturated, and phenols. A linkage urethane is produced by reacting an isocyanate group,-N = C = O with a hydroxyl (alcohol) group,-OH. Polyurethanes are produced by the reaction of polyaddition of a polyisocyanate with a polyalcohol (polyol) in the presence of a catalyst and other additives. In this case, a polyisocyanate is a molecule with two or more isocyanate functional groups, R-(N = C = O) n ≥ 2 and a polyol is a molecule with two or more functional hydroxyl groups, R'-(OH) n ≥ 2. The reaction product is a polymer which contains the urethane RNHCOOR-'. Isocyanates react with any molecule containing a hydrogen active. Importantly, isocyanates react with water to form a bond urea and carbon dioxide, but also react to form polyureas polyetheramines. Commercially, polyurethanes are produced by reacting a liquid isocyanate with a liquid mixture of polyols, catalysts and other additives. These two components are known as a polyurethane system, or simply a system. The isocyanate is commonly known in North America as the "A-team" or simply "iso. The mixture of polyols and other additives commonly known as the "B side" or the cops. This mixture could also be called a resin "or resin "mix." In Europe, the meanings of 'A-side "and" side B "are reversed. Resin mixture of additives may include chain extenders, cross linkers, surfactants, flame retardants, blowing agents, pigments and fillers.

The first essential component of a polyurethane polymer is the isocyanate. Molecules containing two isocyanate groups are called diisocyanates. These molecules are also known as monomers or monomer units, since they themselves are used to produce polymeric isocyanates that contain three or more isocyanate functional groups. Isocyanates are classified as aromatic as the diisocyanate diphenylmethane (MDI) or toluene diisocyanate (TDI), or aliphatic such as hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI). An example of an isocyanate polymer is polymeric diphenylmethane diisocyanate, a mixture of molecules with two, three, and four or more isocyanate groups, with an average functionality of 2.7. Isocyanates can be further modified in part, reacting with a polyol to form a prepolymer. A quasi-prepolymer is formed when the stoichiometric ratio isocyanate to hydroxyl groups is greater than 2:1. A true prepolymer is formed when the stoichiometric ratio equals 2:1. The main features of isocyanates is its molecular backbone, NCO% content, functionality, and viscosity.

The second essential component of a polyurethane polymer is the polyol. The molecules that contain two hydroxyl groups are called diols, which have three hydroxyl groups are called triols, etc. In practice, polyols are distinguished from those of short chain and low molecular weight glycol chain extenders and cross linkers such as ethylene glycol (EG), 1,4-butanediol (BDO), diethylene glycol (DEG) glycerin, and trimethylol propane (TMP). Polyols are polymers in their own right. They are formed by free radical addition of propylene oxide (PO), oxide ethylene (EO) in a hydroxyl or amine containing initiator, or polyesterification a di-acid such as adipic acid, with glycols such as ethylene glycol or dipropylene (DPG). Polyols extended with PO or equality of opportunity are polyether polyols. The polyols are formed by polyesterification polyester polyols. The choice of initiator, thinner, and the molecular weight of polyol greatly affect its physical state and physical properties of the polyurethane polymer. The main characteristics of polyols are their molecular backbone, initiator, molecular weight, primary hydroxyl groups%, functionality and viscosity.
PU mechanism catalyzed reaction dioxide gas tertiary amine carbon formed by reaction of water and isocyanate
The polymerization reaction is catalyzed by tertiary amines, as dimethylcyclohexylamine, organometallic and salts, as dibutyltindilaurate. Moreover, the catalysts can be chosen depending on whether they favor the urethane (gel) reaction, as diazobicyclooctane, or urea (Blow) reaction, bis-dimethylaminoethylether, or specifically direct the isocyanate trimerization reaction, such as potassium octoate.

One of the polyurethanes most desirable attributes is its ability to become foam. Blowing agents such as water, some halocarbons such as HFC-245fa (1,1,1,3,3-Pentafluoropropane) and HFC-134a (1,1,1,2-tetrafluoroethane), and hydrocarbons such as n-pentane, can be incorporated into poly side or added as an auxiliary power. The water reacts with isocyanate to create carbon dioxide gas, which fills and expands cells created during the mixing process. The reaction is a three-step process. A water molecule reacts with an isocyanate group to form a carbamic acid. Carbamic acids are unstable and decompose to form carbon dioxide and an amine. The amine reacts with more isocyanate to give a substituted urea. Water has a very low molecular weight, so even if the weight percent of the water may be small, the molar ratio of water can be high and significant amounts of urea produced. Urea is very soluble in the reaction mixture and tends to form separate "hard segment" phases mostly polyurea. The concentration and organization of these phases polyurea may have a significant impact on the properties of the polyurethane foam. [11 Halocarbons] and hydrocarbons are chosen so that have boiling points at or near room temperature. As the polymerization reaction is exothermic, these blowing agents volatilize in a gas during the reaction process. Fill and expand the polymer matrix, creating a foam. It is important to know that blowing gas does not create the cells foam. Rather, they are formed during the mixing process of nucleation sites that the blowing gas fills and expands. Indeed, microcellular foams are high density can be formed without the addition of blowing agents or mechanically foaming nucleating polyethylene mixture before use.

(2) The use of polyurethane

1. Furniture
2. Car Seats
3. Varnish
4. Computer mouse pads
5. Glue
6. Wheels
7. Casas, sculptures and decorations
8. Boats
9. construction sealants and fire stop
10. Tennis grips
11. Electronic Components
12. Binding of the industry
13. Watch band packing

1.Furniture

Polyurethane is also used in furniture manufacture for casting soft edges around the tables and the panel that are stylish, durable and prevent injury. These are used in the tables of school, hospital and furniture and bank counters stores and displays.

Much of the foam used in chairs, sofas, mattresses and sacks are Comfortable polyurethane foam. This type of foam is made by polyols mixture, diisocyanates, catalysts, foaming agents and other additives and allowing the resulting foam to rise freely. This can be done in a batch process in blocks relatively small foam made in a mold open top, or continuously, where the components are poured onto an inclined moving belt. The foam is cut to shape and size intended for use in the manufacture of furniture.

Safety concerns about the flammability of polyurethane foam, especially upholstered furniture, sometimes requires the addition of flame retardant foam.

Polyurethane is in other countries like the Netherlands used as a floor solution for homes, offices, museums.

2. Car Seats
flexible polyurethane foams and semi-flexible components are widely used for car interiors and seats, headrests, armrests, roof liners and instrument panels

Polyurethane foam in the bottom half of the mold in which it was made. Once mounted on a chair self, this foam makes up the back seat. The side facing rear seat is below the surface of the foam in the mold upside down. The two holes in the foam the top of the image are to the headrest posts.

Foam after removal from the mold.

Polyurethanes are used to make seats car dramatically. The seat manufacturer has a mold for each seat model. The mold can be closed a "spoon" type of structure that would cast Quick seat cushion, the so-called flexible molded foam, which is then upholstered after removal from the mold.

You can combine these two steps, called "in-situ, foam, fabric or direct molding. In this case, the inner surfaces of the mold with hundreds of small holes that are connected to a manifold vacuum. This creates a constant flow of air from the center of the mold of multiplicity. The operator first places a complete seat assembly, completely covered in mold-mounted and adjusted to the manifold vacuum pulls the seat cover tight against the mold surface. In some operations, this effect is enhanced by the addition of a thin film flexible plastic material as a support to help the vacuum work more effectively. When the seat cover is in place, the operator places the structure seat on the metal mold and the mold is closed. At this point the mold contains what could be viewed as a seat "hole", a fabric seat position correct the manifold vacuum and containing a hollow space with the metal structure in place.

The next step is to inject the chemical mixture of polyurethane in the mold cavity. This is a mixture of two parts that accurately measures through a mixing head. Then the mold is maintained at a predetermined reaction temperature chemical mixture until the foam has filled the mold, and formed soft foam stability. The time required is two to three minutes, depending on seat size and formulation needs and operating conditions. Then the mold is usually opened slightly for a minute or two for an additional curing time before upholstered seat integral withdrew. The operator trims excess fabric cover any seat and puts the finished seat on a conveyor belt.

3 Varnish

polyurethane materials are commonly formulated as paints and varnishes for finishing coats to protect or seal wood. This gives rise to its use on a hard surface, resistant to abrasion, and durable coating that is popular for hardwood floors, but considered by some to be difficult or unsuitable for finishing furniture or other items detailed. In connection oil or shellac varnishes, polyurethane varnish forms a harder film which tends to de-laminate if subjected to heat or shock, fracturing the film and leaving white spots. This increases the tendency when applied over softer woods like pine. This is also partly due to lower penetration of the polyurethane wood. Various priming techniques are employed to solve this problem, including the use of certain oil varnishes, specified "Dewaxing" shellac, clear epoxy penetrating, or "oil-modified" polyurethane designed for that purpose. Polyurethane varnish may also lack the "hand-rubbed" brightness drying oils as linseed or tung oil, in contrast, however, is capable of much faster and higher "build" of film making in two layers which may require multiple applications of oil. Polyurethane can also be applied on a pure oil finish, but due to the relatively slow time curing of the oils, the presence of volatile byproducts of curing, and the need for oil prolonged exposure to oxygen, care must be taken that oils are sufficiently cured to accept the polyurethane.

Unlike drying oils and alkyds which cure, after evaporation solvent, by reaction with oxygen from the air, polyurethane coatings cure after evaporation of the solvent by a variety of reactions chemicals within the original mixture, or reacting with moisture in the air. Certain products are "hybrids" and combine the various aspects of components from their parents. "Oil-modified" polyurethanes, either by water or solvent, are currently the most widely used wood finish floor.

Outside the use of polyurethane varnish may be problematic because of its susceptibility to deterioration through exposure to ultraviolet light. It should be noted, however, that all transparent or translucent glazes, and indeed all film-polymer coatings (iepaint, stain, epoxy, synthetic plastic, etc.) are susceptible to this damage in varying degrees. The pigments in paints and stains protect against UV rays, while UV-absorbers are added to the polyurethane and other varnishes (in particular, "Spar" varnish) to work against UV rays. Polyurethanes are typically the most resistant to exposure water, high humidity, extreme temperatures, and mold or mildew, which also adversely affect the performance of varnishes and paints.

4.Computer pads mouse
Polyurethane is used in the bottom of some mouse pads.

5.Glue
Polyurethane is used as an adhesive, especially as glue for woodworking. Its main advantage over the tails of more traditional wood is its resistance to water. It was introduced in the general market of North America in the 1990s as Gorilla Glue and Excel, but has been used longer in Europe.

6.Wheels
Polyurethane is also used in making solid tires. modern roller skating and skateboarding became economical only with the introduction of strong and parts of abrasion-resistant polyurethane. Other constructions have been developed for the tires and microcellular foam variants are widely used in tires on wheelchairs, bicycles and other uses. These types of foam of the latter are also widely found in car steering wheels and interior and exterior car parts, including bumpers and fenders.

7.Houses, sculptures and decorations
The walls and ceiling (not just insulation) of futuristic Xanadu House were built in polyurethane foam. vaulted ceilings and other odd shapes are easier to foam than with wood. Foam was used to construct buildings in a strange way, statues and decorations in the Seuss Landing section of the Islands of Adventure theme park. Specialty manufactures rigid foam foam selling carved wooden replace the sign and the 3D industry topography.

8.Watercraft
Some surfboards are made with a solid polyurethane core. A rigid foam blank is shaped in the form of specification, then covered with fiberglass cloth and polyester resin.

The Boston Whaler boat's hull is made of polyurethane foam inserted into a skin fiberglass. The foam provides strength, buoyancy and acoustic insulation.

9.Construction sealants and stop the fire

Head of the wall common Firestop: pervasive presence demonstrates the need for both operational and test of compatibility between the joint sealant and mechanical / electrical through-the penetrations. In other words, it is easier to insist on the use of firestops participation can also be used for penetration of the stamps, otherwise piercing can be managed by mechanical and electrical subtrades unintentionally void the fire resistance rating of the wall, which jeopardizes the fire safety plan in place for an entire building.

Fire Chief common wall penetrated by both electrical and mechanical services, which demonstrates the need for interoperability and tested the fire from penetrating the firewall system and joint, whether electrical, mechanical or structural.

Polyurethane sealants are available in 1, 2 and even 3 part systems, either in cartridge, bucket or drum format. sealants are also sold to backfire applications. Obviously, the sealant itself offers no serious obstacle to the fire as their hydrocarbon bonds readily support combustion. However, when backed by inorganic insulation such as rock wool or ceramic fiber, can act as an effective seal to keep out smoke and hose stream, especially in the joints inorganic. It is, however, it is advisable to avoid direct contact with sharp metal and penetration through cables, and the heat carried by the piercing may endanger the sealant. This, however, requires great vigilance. Specifically with concrete or concrete masonry joints, however, that are free of mechanical or electrical pervasive, that works well and reliably. Like all products and passive fire protection systems, the key to compliance code can be demonstrated in the limit.

10.Tennis Grips
Polyurethane has been used to make several Tennis Overgrips as Supergrap Yonex, Wilson Pro Overgrip and grips many others. These handles are highly extensible to ensure adherence carefully wrapped around the racket handle.

11.Electronic Components
Often electronic components are protected from environmental influences and mechanical shock by enclosing them in polyurethane. Polyurethanes are usually selected for excellent abrasion resistance, good electrical properties, excellent adhesion, impact resistance, and low temperature flexibility. The disadvantage of polyurethanes is the limited upper service temperature (usually 250 ° F (121 ° C)). In the production of electronics manufacturing would willing to buy one of urethane (resin and catalyst) is mixed and poured into the assembly of the circuit (see casting resin). In most cases, the assembly final circuit would be irreparable after the urethane has cured. Due to its physical characteristics and low cost properties, polyurethane encapsulation (for pots) is a popular choice in the automotive manufacturing sector in automotive circuits and sensors.

Industry 12.Bookbinding
On the road a new and better glue for bookbinders, a new adhesive system was first introduced in 1985. The basis for this system is polyether or polyester, while those of polyurethane (PUR) is used as prepolymer. Its special feature is the coagulation temperature and reaction to moisture.

1st Generation (Drupa 1988) – Low starting solidity – high viscosity – Drying time over three days

2nd generation (drupa 1996) – Under the soundness starting – High viscosity – Drying time of less than 3 days

3rd Generation (drupa 2000) – Good starting solidity – Low viscosity – time dried between 6 and 16 hours

4th generation (this) – Good starting solidity – Very low viscosity – Drying time is reached in a few seconds due to Dual-Core-Systems

Advantages of polyurethane glue in the bookbinding industry: PUR is real wonder compared to hotmelt and cold glue. Due to lack moisture glue, papers with wrong grain direction can be processed without problems. Even the printed paper and can bind supercalandered smoothly. It is the cheapest glue with a theoretical application of 0.01 mm thickness. But in reality it is not possible to apply less than 0.03 mm. The polyurethane adhesive is a very stable climate and resistant to temperatures of -40 ° C to 100 ° C.

13.Watch Band adjustment
Polyurethane is used as a wrapper for bracelets black clock on the main material, which is usually stainless steel. It is used for comfort, style and durability.

 

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Casting Resin and Liquid Plastic