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POLYURETHANE-28 is a class of polymers composed of organic units joined by carbamate (urethane) links.
In contrast to other common polymers such as polyethylene and polystyrene, polyurethane refers to a group of polymers.
Unlike polyethylene and polystyrene, POLYURETHANE-28 can be produced from a wide range of starting materials, resulting in various polymers within the same group.
CAS: 9009-54-5
MF: C3H8N2O
EINECS: 210-898-8
Synonyms:Polyisocyanurate resins;Polyurethanes, cellular;PU foam;The following companies react isocyanates or prepolymers with polyols to produce polyurethane foams. The list is incomplete.;POLYURETHANEOLIGOMERS;POLYURETHANEVARNISH;POLYURETHANELACQUER;Polyurethane foam: (Urethane polymers)
This chemical variety produces POLYURETHANE-28 with different chemical structures leading to many different applications.
POLYURETHANE-28 include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL).
Foams are the largest application accounting for 67% of all POLYURETHANE-28 produced in 2016.
A POLYURETHANE-28 is typically produced by reacting a polymeric isocyanate with a polyol.
Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers.
Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.
Global production in 2019 was 25 million metric tonnes, accounting for about 6% of all polymers produced in that year.
POLYURETHANE-28 Chemical Properties
Bulk density: 0.08g/cm3
Form: foam
Stability: Stable. Combustible. Incompatible with strong oxidizing agents.
InChI: InChI=1S/C3H8N2O/c1-2-5-3(4)6/h2H2,1H3,(H3,4,5,6)
InChIKey: RYECOJGRJDOGPP-UHFFFAOYSA-N
CAS DataBase Reference: 9009-54-5
IARC: 3 (Vol. 19, Sup 7) 1987
POLYURETHANE-28 foams are resistant to a wide range of solvents.
In this respect, polyester foams are generally superior to polyether foams, particularly in resistance to dry cleaning solvents.
POLYURETHANE-28 foams are subject to degradation by aqueous acids and alkalis and steam. Ester, amide and urethane groups represent sites for hydrolytic attack.
Since the ether group is not readily attacked, polyether foams are generally more resistant to hydrolysis than polyester foams.
Uses
Prosthetic aid (internal bone splint).
POLYURETHANE-28 resins and foams are two important industrial polymers.
They can be produced as rigid, semirigid, or elastic foams or resins, which give PUR many versatile commercial uses.
POLYURETHANE-28 can be found in furniture, bedding material, automotive sealing material, adhesives, carpet, packaging material and coatings, and many other products.
POLYURETHANE-28 is favored industrially because of its resistance to oil, light, and solvents, in addition to its strength and flexibility.
These polymers are formed by polyaddition reactions between a diisocyanate and a polyhydroxyl compound, such as a polyol.
Several isocyanates (tolylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, etc.) are used in preparing polyurethanes.
All are lowviscosity liquids at room temperature with the exception of 4, 4-diphenylmethane diisocyanate (MDI), which is a crystalline solid.
The aromatic isocyanates are more reactive than the aliphatic isocyanates and are widely used in urethane foams, coatings, and elastomers.
The cyclic structure of aromatic and alicyclic isocyanates contributes to molecular stiffness in polyurethanes.
Flexible polyurethane foams are open-cell structures which are usually produced with densities in the range 24-48 kg/m3 (1.5-3Ib/ft3).
The major interest in flexible foams is for upholstery applications and thus the loadcompression characteristics are of importance.
Preparation
POLYURETHANE-28 foams are produced by forming a polyurethane polymer concurrently with a gas evolution process.
Provided these two processes are balanced, bubbles of gas are trapped in the polymer matrix as POLYURETHANE-28 is formed and a cellular product results.
The matching of the two reactions is essential for the formation of satisfactory foams.
If the evolution of gas is too rapid, the foam initially rises well but then collapses because polymerization has not proceeded sufficiently to give a matrix strong enough to retain the gas.
If polymerization is too fast, the foam does not rise adequately.
By selection of appropriate reactants, POLYURETHANE-28 is possible to prepare foams of varying degrees of cross-linking.
Slightly cross-linked products are flexible whilst highly cross-linked products are rigid. Both flexible and rigid polyurethane foams are of commercial importance.
