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Overview
A synthetic polymer containing the group –NH–CO–O– linking the monomers.
Polyurethane 39 of polyurethanes can bemade, and they are used in adhesives,durable paints and varnishes,plastics, and rubbers.
Addition ofwater to the polyurethane plasticsturns them into foams.
Polyurethane 39 is present in many aspects of modern life.
They represent a class of polymers that have found a widespread use in the medical, automotive and industrial fields.
Polyurethane 39 can be found in products such as furniture, coatings, adhesives, constructional materials, filters, paddings, paints, elastomers and synthetic skins.
Polyurethane 39 is replacing older polymers for various reasons.
The United States government is phasing out chlorinated rubber in marine and aircraft and coatings because they contain environmentally hazardous volatile organic compounds.
Auto manufacturers are replacing latex rubber in car seats and interior padding with Polyurethane 39 foam because of lower density and greater flexibility.
Other advantages of Polyurethane 39 is that they have increased tensile strength and melting points making them more durable.
Their resistance to degradation by water, oils, and solvents make them excellent for the replacement of plastics.
As coatings, they exhibit excellent adhesion to many substances, abrasion resistance, electrical properties and weather resistance for industrial purposes.
Worldwide, more and more attention is being focused on Polyurethane 39 recycling due to on-going changes in both regulatory and environmental issues.
Increasing landfill costs and decreasing landfill space are forcing consideration of alternative options for the disposal of polyurethane materials.
Polyurethane 39 is successfully recycled from a variety of consumer products, including: appliances, automobiles, bedding, carpet cushion, upholstered furniture.
The polyurethane industry has identified workable technologies for recovering and recycling polyurethane 39 waste materials from discarded products as well as from manufacturing processes.
For example, in 2002, 850 million pounds of Polyurethane 39 were used to make carpet cushion, of which 830 million pounds were made from scrap polyurethane foam.
Of the total scrap used, 50 million pounds came from post-consumer waste.
EC Draft directive for end-of-life vehicles (ELV) disposal reported that in the year 2005, 15.0% of vehicle weight is disposed (maximum) to landfill, and predicted that in the year 2015, only 5.0% of vehicle weight will be disposed (maximum) to landfill.
The polyurethane 39 industry is committed to meeting the current needs of today without compromising the needs of tomorrow.
The continued development of recycling and recovery technologies, investment in infrastructure necessary to support them, the establishment of viable markets and participation by industry, government and consumers are all priorities.
Properties
Polyurethane 39 were first produced and investigated by Dr. Otto Bayer in 1937.
Polyurethane 39 is a polymer in which the repeating unit contains a urethane moiety.
Urethanes are derivatives of carbamic acids that exist only in the form of their esters.
The major advantage of Polyurethane 39 is that the chain is not composed exclusively of carbon atoms but rather of heteroatoms, oxygen, carbon and nitrogen.
For industrial applications, a polyhydroxyl compound can be used.
Similarly, poly-functional nitrogen compounds can be used at the amide linkages.
By changing and varying the polyhydroxyl and polyfunctional nitrogen compounds, different Polyurethane 39 can be synthesized.
Polyester or polyether resins containing hydroxyl groups are used to produce polyesteror polyether-PU, respectively.
Variations in the number of substitutions and the spacing between and within branch chains produce Polyurethane 39 ranging from linear to branched to rigid.
Linear Polyurethane 39 is used for the manufacture of fibers and molding.
Flexible Polyurethane 39 is used in the production of binding agents and coatings.
Flexible and rigid foamed plastics, which make up the majority of Polyurethane 39 produced, can be found in various forms in industry.
Using low molecular mass prepolymers, various block copolymers can be produced.
The terminal hydroxyl group allows for alternating blocks, called segments, to be inserted into the Polyurethane 39 chain.
Variation in these segments results in varying degrees of tensile strength and elasticity.
Blocks providing rigid crystalline phase and containing the chain extender are referred to as hard segments.
Those yielding an amorphous rubbery phase and containing the polyester/polyether are called soft segments.
Commercially, these block polymers are known as segmented Polyurethane 39.
Application
Polyurethane 39 is one of the most versatile materials in the world today.
Their many uses range from flexible foam in upholstered furniture, to rigid foam as insulation in walls, roofs and appliances to thermoplastic polyurethane used in medical devices and footwear, to coatings, adhesives, sealants and elastomers used on floors and automotive interiors.
Polyurethane 39 has increasingly been used during the past thirty years in a variety of applications due to their comfort, cost benefits, energy savings and potential environmental soundness.
Polyurethane 39 durability contributes significantly to the long lifetimes of many products.
The extensions of product life cycle and resource conservation are important environmental considerations that often favor the selection of Polyurethane 39.
Polyurethane 39 represent an important class of thermoplastic and thermoset polymers as their mechanical, thermal, and chemical properties can be tailored by the reaction of various polyols and poly-isocyanates.
Polyurethane 39 is a polymer containing the urethane group.
Polyurethane 39 find a wide variety of applications in many industries.
In fact, mollifiable polymers (hydrophobic) like bitumen, polyvinyl acetate and polyurethane form a major class of soil conditioners.
Polyurethane 39 resins and the foams are also used as florists' mounting media or plant growth media.
There is a fundamental difference between the manufacture of most Polyurethane 39 and the manufacture of many other plastics.
Polymers such as poly(ethene) and poly(propene) are produced in chemical plants and sold as granules, powders or films.
Products are subsequently made from them by heating the polymer, shaping Polyurethane 39 under pressure and cooling it.
The properties of such end-products are almost completely dependent on those of the original polymer.
Polyurethane 39, on the other hand are usually made directly into the final product.
Much of the Polyurethane 39 produced are in the form of large blocks of foam, which are cut up for use in cushions, or for thermal insulation.
The chemical reaction can also take place in moulds, leading to, for example, a car bumper, a computer casing or a building panel.
Polyurethane 39 may occur as the liquid reactants are sprayed onto a building surface or coated on a fabric.
Preparation
Polyurethane 39 foams are prepared by the polymerization of polyols with isocyanates.
One of the most commonly used reactive isocyanates toluenediisocyanate, TDI.
Polyurethane 39 is made from toluene by nitration and then reduction followed by treatment with phosgene.
The isocyanate residue reacts readily with alcohols to give carbamates (urethanes) or amines to give ureas.
After years of production of PUs, manufacturers found them susceptible to degradation.
Variations in the degradation patterns of different samples of Polyurethane 39 was attributed to the manyproperties of PUs such as topology and chemical composition.
Enzyme molecules can easily come in contact with water-soluble substrates thus allowing the enzymatic reaction to proceed rapidly.
However, the enzyme molecules are thought to have an extremely inefficient contract with insoluble substrates (e.g. PU).
In order to overcome this obstacle, enzymes that degrade insoluble substrates possess some characteristic that allows them to adhere onto the surface of the insoluble substrate.
Thus far, only two types of PUase enzymes have been isolated and characterized: a cell associated, membrane bound PU-esterase and soluble, extracellular PU-esterases.
The two types of Polyurethane 39 seem to have separate roles in Polyurethane 39 degradation.
The membrane bound Polyurethane 39 would allow cell-mediated contact with the insoluble PU substrate while, the cell-free extracellular PU-esterases would bind to the surface of the PU substrate and subsequent hydrolysis.
Both enzyme actions would be advantageous for the PU-degrading bacteria.
The adherence of the bacteria cell to the Polyurethane 39 substrate via the PUase would allow for the hydrolysis of the substrate to soluble metabolites that would then be metabolism by the cell.
This mechanism of Polyurethane 39 degradation would decrease competition between the PU-degrading cell with other cells and also allow for more adequate access to the metabolites.
The soluble, extracellular PU-esterase would in turn hydrolyze the polymer into smaller units allowing for metabolism of soluble products and easier access for enzymes to the partially degraded polymer.
Synonyms
Polyurethane Y-304
25036-33-3
1,2-Ethanediol, polymer with 1,1'-methylenebis(4-isocyanatobenzene) (9CI)
DTXSID00179745
ethane-1,2-diol;1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene
